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Engine in a Box
Notes and
observations
Online you can find just about anything you want concerning the
engine in your boat. Just type into the search engine the make and model and
you can find an enormous amount of information. This page concerns itself with
the cage (engine room) that this animal (gas or diesel) has to live
in. Plus, how to give it the best care and feeding possible, before you
have to climb in there and play doctor to it.
 
First, like any
breathing thing, it's got to have air. The power rating of marine engines, which is
regulated by the volume setting of the fuel injection pump, is set for the
climatic conditions in which they are to operate. Usually, factory settings are
at 60F to 70F. If the air in the engine room becomes unduly heated, the engine
is unable to induct sufficient weight of air to provide complete combustion of
its designed fuel injection volume and it will not develop its designed
horsepower and R.P.M. The "British Standard" of derating for atmospheric
temperature is 2% per 10°F and it will readily be seen that if an engine be
operated in a 120°F atmosphere when it is designed for a 60°F atmosphere it
should have its fuel supply reduced by 12% and, consequently, its power
output reduced.
The atmospheric pressure, temperature and humidity all affect the
density of the air. On a hot or a moist day, the air is less dense. That
reduction in air density reduces the amount of oxygen available for combustion
and therefore results in incomplete combustion and reduces the engine
horsepower and torque. For tweaking the fuel/air mixture, the air density is
the most important consideration.
This incomplete combustion has a cumulative effect on engine
room temperature. The products of incomplete combustion can cause lubricant contamination,
internal deposits and fouling, also high piston, valve and sprayer
temperatures, etc., and may lead to unreliability and high maintenance.
So, when your down in the engine room or open that little engine
hatch, how hot is it in there? Most of the ones I've been in, seem like a
Turkish bath. What can you do? First, check to see where the engine air intake
gets its air from. If it's the cage (room) itself, how about making sure that
it has some nice intake and exhaust air supply hoses. Preferably, that intake
hose is real close the air filter/intake on the engine. That air is maybe 30-40
degrees cooler than the rest of engine room. If it's a long intake hose, make
sure it's has straight as possible to that nice big dorade on deck.
 
No so good to have a 6" hose for a 300 horse power engine that
runs 8 feet with three, 90 degree turns and hooked to a low profile dorade
that has a cooler in front of it! Kinda like you or me breathing out of a
8 foot straw! Do you have too many bends, small diameter hose; think about
adding a power fan to it. I installed one to a 6" hose on a 50 horse power
engine (an engine compartment vent fan, mounted in reverse) cruising the
South Pacific and it helped with engine combustion and cooling the boat at its
heat generating source, the engine. Basically, you want to get that air filter
to get the most and the coldest air possible. (That's part of what a
turbocharger and intercooler is about) Of course, you must ensure the air
filter is cleaned regularly.
So now that it's
breathing OK, what are we feeding it?Some diesel engine
problems are related to fuel problems and now "oxygenated"
gasoline is having some of the same issues. Diesel fuel contamination
problems have two different perspectives: biology and chemistry.
Thinking you have a chemical problem when you have a biological problem and
treating it with the wrong chemical cleaner will not solve your problem and may
compound it.
The most prominent
problem is chemical and lies in the creation of "asphaltene."
Asphaltenes (aka diesel sludge) looks like algae but there is NO ALGAE in
diesel fuel. Asphaltenes are created by either the natural aging of
diesel fuel, by simply adding the wrong fuel additives or mixing perfectly
good clean fuels from two different suppliers. As the fuel further
deteriorates, it darkens, produces a foul odor, and often causes diesel engines
to smoke. This is a direct result of the early-stage fuel clustering and
passing through the filtration systems and into the combustion chamber. These
clusters cause greater difficulty as they increase in size, failing to burn
correctly, thereby exiting the system as unburned fuel in the form of smoke.
This problem is exacerbated as the clusters eventually reduce the fuel flow to
the point of clogging the filters. Filtration does not solve the core issue of
excessive sludge in the fuel and tank.
The other problem
that affects diesel fuel is a biological problem... "Fuel Bugs."
There are many types of Fuel Bugs (aka bacteria, fungus and mold), that can
live in diesel fuel. A small amount of water from either condensation or from
entering the tank through a vent can start your Fuel Bug colony growing.
"Fuel Bugs", bacteria and fungus, primarily Cyanobacteria, in diesel
fuel are less prominent that Asphaltenes. Most diesel users have very little
knowledge of this costly problem. There are over 100 types of Fuel Bugs that
can live in diesel fuel. Fuel Bugs feed on the oil in the fuel and use the
water in the fuel for their oxygen supply. They grow in your fuel at different
rates and can easily cost thousands of dollars in damage.
So, fuel filters are
a start. High quality remote Racors or even those inexpensive ones
you can by at NAPA will help keep the engine running, till they clog! You
can use asphaltene dispersants and fuel biocides, but make sure you know
what the problem is! If the fuel tank is
badly contaminated you could install one of the new onboard fuel treatment
systems or you can try fuel polishing. Then, you must treat the fuel
continually. Biocides eat bugs and when those few ounces of biocides you added
to your fuel tank have eaten all they can, they full and you have to add more
biocides. Also, when you add the sludge dispersant to your 500 gallon tank,
then used 150 gallons, and then let it sit again, it just got older and dropped
out more asphaltenes. The fuel is never in a stagnant state, it may be
changing slowly, but it's changing.
ALERT! ETHANOL IN HAWAII
For those having gasoline engines, inboard or outboard, I have
added some info from the petroleum, ethanol, engine, and marine industry. Read
this stuff and check the internet for your particular engine, boat fuel tank,
etc.
Beginning April 2, 2006, at least 85 percent
of Hawaii's gasoline must be E-10 Unleaded: gasoline containing 10% ethanol.
Ethanol, a renewable fuel, is a normal component of today's gasoline. All
gasoline-powered vehicles sold in the United States are designed to use E-10 Unleaded. Gasoline containing up to 10%
ethanol has been in increasing use in the United States since the late 1970s. In 2005, about 40% of the gasoline used in
the U.S. contained ethanol.
In some states and large metropolitan areas, all of the gasoline
contains ethanol, and has for several years. Blends have been available in over
41 states for more than 10 years, and in over 21 states for more than 20 years.
Information from these areas can help Hawaii gasoline retailers,
automotive industry, regulators, and the public to become familiar with the
fuel.
What is ethanol, and ethanol-blended
fuel? Ethanol is highly refined beverage (grain) alcohol, approximately
200 proof, and can be made from natural products such as corn, sugar, and
wheat. Ethanol that is used for fuel has been denatured with hydrocarbon,
rendering it unsafe to drink.
E10 Unleaded fuel is a mixture of 10% ethanol and 90% unleaded
gasoline (E for ethanol and 10 is for 10%). Automobiles that normally use
unleaded gasoline for fuel can also run using E10 fuel. E10 is NOT considered
an alternative fuel (it's still 90% gasoline).
Another type of ethanol-blended fuel is E85. E85 refers to a mixture
of 85% ethanol and 15% unleaded gasoline. E85 is an ALTERNATIVE FUEL and is for
use in ALTERNATIVE FUEL and FLEXIBLE FUEL vehicles.
FUEL FILTERS
Several issues
come into play with fuel filters and the conversion to an ethanol blended fuel.
There is a sediment issue when an ethanol conversion first takes place. Ethanol
acts as a cleaning agent, breaking loose built-up sediments from the tank and
other areas and leading to an initial period where fuel filters tend to clog
(the same can also happen in automobiles). After the sediment has worked its
way out, Does ethanol lead to plugged fuel filters?
Ethanol is an efficient solvent, and therefore, the use of
ethanol-blended fuel may result in loosened contaminants and residues
collecting in the fuel filter. The fuel filter may need to be changed following
the first full tank of ethanol-blended fuel has been used. After this, the fuel
filter's normal maintenance schedule may be followed. This problem is very
uncommon, and is likely to happen only in older cars that used leaded gasoline
water becomes a consideration.
FUEL TANKS
BoatU.S. Magazine has recently reported a
preliminary investigation into claims about gasoline containing ethanol causing
older fiberglass fuel tanks to fail. The ethanol additives could reportedly
lead to weakened tank walls and bottoms that potentially could lead to a leak
or explosion.
Industry-wide changes in fiberglass
resin formulations made in the mid-1980s could be a beneficial ally in
correcting this condition. The problem appears only to occur in fiberglass
tanks manufactured prior to the changes. It is also important to note that
diesel fuel systems do not appear to be affected.
In preliminary reports, BoatU.S. did
confirmed the claims of gasoline leaking into the bilge following tank wall
failure. The reports also indicated a tar-like substance that produced hard
black deposits which destroyed the engine through continual damage to the
intake valves and pushrods. BoatU.S. speculates the tar-like substance is
created by a chemical reaction between the older fiberglass resin and the
ethanol.
Boat owners should be aware of signs of
engine backfiring and hard or sluggish starting in which the motor turns over
slowly as though the battery is weak. In addition, affected engines may not
reach their rated RPM. Chuck Fort, associate editor of Seaworthy, the damage
avoidance newsletter from BoatU.S., stated, "Ironically, the substance seems to
pass through fuel filters leaving no tell-tale marks - some have appeared clean
on our reports. The only way to know for certain is to pull the carburetor and
inspect the underside for a black, gummy film which can indicate a serious
problem." BoatU.S. is recommending all early 1980s or early vessels with
fiberglass gas tanks be stored empty over the winter.
The investigation is
ongoing, but it appears that 10% ethanol gasoline, which was introduced in the
Long Island area to replace gas additive MTBE in late 2004, may be attacking
the resins used in older fiberglass gas tanks. These tanks were standard
equipment on some Hatteras and Bertram models and may be present on other boats
of the same era. Diesel tanks are not affected.
The engine damage
appears to be due to a tar-like substance--possibly from the chemical reaction
between the resin and ethanol--causing hard black deposits that damage intake
valves and pushrods, ultimately destroying the engine. Early symptoms may
include engine backfiring and hard or sluggish starting in which the engine
turns over slowly. Affected engines may not reach their rated rpm.
Technical info:
The Aussie
government on outboards,
http://www.environment.gov.au/atmosphere/fuelquality/publications/marine/index.html
and the engineering department of Dartmouth College. (This is a 117 page download)
http://www.dartmouth.edu/~ethanolboat/Ethanol_Outboard_Final_Report.pdf
What is phase separation?
When E10 fuel is contaminated with over 0.5% water, the ethanol and
water mixture will separate from the gasoline and fall to the bottom of the gas
tank. The fuel system must then be drained and new fuel added. Before using
ethanol-blended fuel for the first time in an older small engine, all water
should be removed from the tank.
What do we do now?
For now, as of the end of March 2006, not a lot can be done for that
fiberglass tank. The application of some type of coating to the interior of a
FRP tank would be the easiest even with the additional labor of cutting off the
top for access. The problem is, no coating is available as yet, WEST SYSTEMS says no...
All types and variations of tanks have
been successfully constructed with WEST SYSTEM Brand epoxy and used in the
field with great results. However, Gougeon Brothers does not condone or
recommend that certain tanks be built because of various issues noted above. In
our testing, various epoxy combinations have proven to be resistant to various
liquids, including gasoline, diesel fuel, motor oil, potable water, sea water,
sewage, gray water, etc. Regarding gasoline specifically, some epoxy
combinations are more resistant than others. With the increasing use of alcohol
and other high-tech additives, we are unsure how the epoxy will resist them in
the future. We do know that many types of alcohol vigorously attack epoxy; we
can only conclude that gasoline with a higher percentage of alcohol may break
down an epoxy coating over a long period of time.
So for now, Watch your fuel filters!
Watch for
fuel leaks!
Watch for performance issues!
If you have older fiberglass built-in fuel tanks, maybe
you need to think about that time when you will have to replace with a
metal tank. As soon as I hear something that is proven to work, I
will post it on the site.
OK, we got that caged
animal breathing correctly; we got it some good food, next, how about we check
the plumbing and make sure we don't have to clean that cage!
Raw Seawater Systems
They are relatively
simple. That raw water pump should not leak anywhere, period. Any
buildup of salt crystals anywhere, is a leak. The impeller that draws the seawater
in must have all its vanes on it or it will cause the engine to overheat. I
prefer the "blue" Globe brand impellers; they say you can run them dry for 15
minutes before they destroy themselves, used them cruising the Pacific and
every time I popped the cover off, it looked new! We have to play plumber
here and take off the cover plate to check, especially if the engine has not
been started in months. Impeller vanes can take a "set" (bend) in the
pump. Don't worry, that plate and the thin gasket, is relatively easy to
reinstall, just don't forget to turn the intake seacock off! Also, make sure the zincs in the heat
exchanger/transmission cooler are still there. Don't want to buy a
expensive heat exchanger because of a couple of $3 zincs! Check the exhaust
mixer, hoses and clamps for leaks and part one is done.
Part two is the fresh
water side of the exhaust. A 50/50 mix
of antifreeze and water is best, according to most engine manufacturers.
Straight water provides no freezing, boil over or corrosion protection. It also
cools less efficiently than the 50/50 mix. It is best to use distilled water
because it is pH neutral, contains no acids, dissolved salts or minerals and
maximizes the coolant life. If you are using a "long-life"
antifreeze, do not mix it with regular antifreeze and visa versa. They are
both made with different ingredients that may neutralize the corrosion
inhibitors and would contaminate the system. If that happens you will have
to drain the complete system and start again.
Long-life antifreezes
advertise they are good for 3-5 years; regular antifreezes are usually only
good for 1 year, whether the engine is run or not! The corrosion inhibitors
dissipate so just because it looks green or red or yellow, does not mean its
protecting the engine from corrosion. You will have to add more corrosion
inhibitors or drain and renew the system.
To add more inhibitors and combat
corrosion, one must monitor the rate of corrosion within the cooling system.
The rate is caused by a number of factors, including the acidity or alkalinity
of the coolant. The acidity and alkalinity is measured on a pH scale and is
very important. If the coolant remains alkaline, corrosion is inhibited but if
it becomes acidic, the coolant begins to eat away at the interior of the
system. Test strips are available online or at some auto parts stores and it's
a simple test. Also, if your engine does not have an overflow system, add one!
The local auto parts store sells a complete kit, plastic tank, bracket, and
hose for under $20 and it's a whole lot easier and safer to glance at the
overflow tank to see if the coolants low, dirty, etc.
The last check is that expansion
tank/radiator cap, the cheapest moving part of the system. When I do
an engine analysis I pressure check the system and many times that 7 lbs.
or 13 lbs. cap will not hold is rated capacity (Gee, it's 10-15-20-30 years
old). Freshwater system are designed to hold a certain amount of
pressure caused by that water/mixture and heat, add a faulty cap, engines
overheat, loose coolant, etc.etc. Stamped right on that cap is the pressure
capacity, the auto parts stores even have them new fangled caps with the
pressure release levers for about $7.00, can make a world of difference!
Wet Exhaust Systems
Carbon monoxide poisoning, excessive heat in compartments, and
reduced engine performance can develop from the lack of good exhaust system
maintenance. We're not talking about anything more extensive then taking a look
once in awhile. Which is usually the problem! A good surveyor will climb around
down there and look, grab, and/or shake every hose clamp and fitting when the
engine is cold and look at them again when the engine is running. It would be
nice to think I never come across problems in exhaust systems but that's not
the real world. Sometime everything appears fit for service until I run a CO
meter at those same fittings and it detects leaks. Most of the time, just
enough to give you a really crappy headache at the end of your day on the
water. So, what to look for...
Exhaust Manifold - Check the tightness
of the attachment nuts and bolts especially on engines which have heavy
manifolds that incorporate header tanks and heat exchangers. Leaking manifold
gaskets are the first signs of loosening.
Freeze Plugs - Check for salt and corrosion on
them little round disks. First signs are usually pin-prick sized holes, or
bubbling of surface paint.
Exhaust Injection Elbow - Salt or corrosion
indicates a leak caused by severe corrosion. First indications are usually
small pin-prick sized holes adjacent to the point where raw water is injected
into the elbow. Soot deposits by the mounting flange indicate a loose joint or
gasket failure. Check tightness of attachment bolts which loosen through high
temperature and settling of thick gaskets. Lots of engine manufactures suggest
you remove and inspect internally every other season.
Hose Clamps - Inspect for corrosion and
cracking. Those nice shiny clamps with the rusted (not stainless) screws...
usually snap or strip when you want to tighten them up some. NFPA 302 4-3 says exhaust hose should always
be double clamped at every fitting throughout it's' length. Put those two
tightening screws on alternating sides, gives you a little more safety factor.
Lift Box/Muffler - Stainless mufflers
suffer from corrosion with stainless corroding from the inside out. I had a
boat where the stainless water lift was a foot above the engine, "rusty" on the
outside, which really had rusted thru the internal pipe. I turned the engine
off and it dropped all its saltwater down the hose, up the injection fitting at
the exhaust manifold, thru the manifold and into the cylinders. Seven days, 2
gallons of WD-40, 15 gallons of oil, 4 oil filters, a million pesos ($650 US)
and countless rags and cleaning stuff fixed it. Hey, it looked okay to
me a 1000 miles earlier when I last checked it. Best fish tacos are in La Paz, while you wait for
parts. Plastic lift boxes and mufflers suffer from split welds mostly through
over tightening of exhaust hose clamps. Glass fiber boxes are usually
maintenance free and provide longer service (part of that $650).
Exhaust Hose - Check for cracking, softness,
delaminating, kinking and corrosion of the reinforcing wire. An SAE J2006
spec'ed wet exhaust hose just can't be strangled, it's like squeezing a metal
pipe.
More info on how to flood your engine
The raw
water flows with the exhaust gases into a water-lift box, also called a water
silencer. The discharge pipe of the water-lift box is set slightly above the
bottom of the box. The water level rises until it blocks the discharge pipe, at
which point the trapped exhaust gases build up sufficient pressure to lift the
water up the exhaust pipe and out of the boat. If the engine is installed below
the waterline, problems can occur. If the engine is at any time below the
waterline, any cooling circuit that allows raw water into the exhaust has the
potential to set up a siphon action. Water may siphon in from the water
injection side; or, if the exhaust outlet is below the waterline, from the
exhaust outlet side. It may be driven up the exhaust pipe by following seas;
or, in an otherwise calm anchorage, be forced up the pipe by repeated wakes
from passing boats or common wave action. This phenomenon is known as a water
hammer. Similarly, on a boat with a generator, backing down can force water
into the generator exhaust.
Repeated
cranking of a difficult to-start engine can pump excessive water into an
exhaust. With every cranking attempt, the raw-water pump will move more water
into the exhaust. In a typical installation, this water will not be pumped out
until the engine fires by which time; there may be enough water in the exhaust
to flood the engine.
A siphon break is a good idea on sail boats and even on some power
boats where the raw-water injection point is above the waterline, making the
development of a siphon theoretically impossible. I believe the recommended
practice is that the injection point is 15" above the waterline. Those
"level state;' calculations made by the builder often do not hold at sea.
The boat may be heavily laden and down a few inches on its waterline. There may
be times when the angle of heel puts the injection point below the waterline, a
particularly likely scenario on twin-engine boats, where the engines are offset
from the centerline. Or, there may be occasions when substantial waves surging
past the boat create sufficient hydrostatic pressure to set up an intermittent
siphon, eventually flooding the engine
To finish up... get down there and take a look, or tell that mechanic
you dropped a hundred dollar bill and will split it with him if he finds it, or
call me.
OIL
With oil at $70.00+ per barrel before refining, it's not time to be
frivolous about crankcase oil. It's also not time to buy that cheap engine oil
you're going to put into the very expensive machinery and diminish its life
span. I came across this website from guy in Europe that explains engine
oil, use, history, specification, and done very well.
http://www.carbibles.com/engineoil_bible.html
My interest with engine oil came from the propane industry 20+ years
ago. At the time we were converting gasoline engines to run on gasoline and
propane or straight propane. Up to that time as far as I was concerned there
were 2 types of oil, oil for gas or diesel engines. Using regular gasoline
motor oil in an engine that injects a vapor not a liquid into a cylinder causes
big changes. Gasoline and diesel motor oil has an "ash" package additive. Ash
is added to oils because of cylinder wash down, (gasoline or diesel that runs
down the inside of the cylinder) and drops into the oil pan. No ash in those
engines gets you really thin oil, oil so thin it's not oil anymore, it's
solvent. In our experience with propane, no cylinders washed down because
propane is a vapor, the oil is not diluted anymore and now the ash is slowly
cooked with engine temperature. You get nice black grease, a "Crisco" kind of
thing, also not a engine oil and nearly impossible for an oil pump to push up
into the cylinder head!
Why, did I tell you all this? To impress upon you to check your
engine manual and if you do not have one, to contact the engine manufacturer,
they have specified exactly what oil to pour into that little monster. Have
question about using the new synthetics; contact them, especially if it's still
in warranty!
Oil additives are numerous, these are just a few I got from the web
and there's plenty more. Some key types, what they do, what they are composed
of, and how they function.
Antiwear and EP Agent - Reduces friction and wear and prevent scoring and seizure. Zinc
dithiophosphates, organic phosphates, acid phosphates, organic sulfur and
chlorine compounds, sulfurized fats, sulfides and disulfides. Chemical reaction
with metal surface to form a film with lower shear strength than the metal,
thereby preventing metal-to-metal contact.
Corrosion and Rust Inhibitor - Prevents corrosion and rusting of metal parts in contact with the
lubricant. Zinc dithiophosphates, metal phenolates, basic metal sulfonates,
fatty acids and amines. Preferential adsorption of polar constituent on metal
surface to provide protective film, or neutralize corrosive acids.
Detergent - Keep surfaces free of deposits. Metallo-organic compounds of
sodium, calcium and magnesium phenolates, phosphonates and sulfonates. Chemical
reaction with sludge and varnish precursors to neutralize them and keep them
soluble.
Dispersant - Keep insoluble contaminants dispersed in the lubricant. Alkylsuccinimides,
alkylsuccinic esters, and mannich reaction products.
Contaminants are bonded by polar
attraction to dispersant molecules, prevented from agglomerating and kept in
suspension due to solubility of dispersant.
Friction Modifier - Alter coefficient of friction. Organic fatty acids and amides, lard
oil, high molecular weight organic phosphorus and phosphoric acid esters.
Preferential adsorption of surface-active materials.
Seal Swell Agent - Swell elastomeric
seals. Alkylated naphthalene and phenolic polymers, polymethacrylates,
maleate/fumerate copolymer esters. Modify wax crystal formation to reduce
interlocking.
Antifoamant - Prevent lubricant from forming a
persistent foam. Silicone polymers, organic copolymers. Reduces surface tension
to speed collapse of foam.
Metal Deactivator - Reduce catalytic
effect of metals on oxidation rate. Organic complexes containing nitrogen or
sulfur, amines, sulfides and phosphates. Form inactive film on metal surfaces
by complexing with metallic ions.
So, gotta degree in chemistry? I sure don't. How do I tell if the
engine is in trouble from the oil its swimming in? Oil analysis! You bought a nice new boat with an engine, a baseline
analysis is a good start, whether the engine was made this year or 20 years ago
in a "new to you" boat. With the metal particle information from an oil
analysis you can get lots of info on where to go from there and what is
happening inside. I used this company, check the info on their website.
http://www.analystsinc.com
Click on SERVICES, then
USED OIL ANALYSIS, then SPECTROCHEMICAL ANALYSIS to see the metal particles
they count and where they come from.
Oil
Changes
Check your manual (again) they will give you an engine hour time limit.
That does not mean "I ran it for 5 hours, 6 months ago, it should be Ok"! That
ash additive package I mentioned above may or may not absorb water from
condensation. A crankcase is not a completely "seal" system so think of the
crank case like a partially covered bucket of oil in your garage. Cruising,
(running the engine daily) I changed the oil every 50 hours and never had a
problem with that part of the system. I don't believe you can change it too
often in the marine environment, especially small engines. You have 2 huge
diesels you say, the big dollar engines? That oil analysis will tell you
exactly when! Filters are specified
by the engine builder, brands won't matter much if you change the oil
regularly, keep the spares in a zip lock bag so as not to absorb ambient
moisture. Cruising, we had them vacuum packed.
Again, monitor that oil, get a baseline oil analysis, then get one
in the oil change time limits (specified by the engine builder) to ensure the
oil is performing correctly in your particular environment and change the
filters often. Otherwise you're guessing and gambling. An analysis is much cheaper than a tow or a
rebuild.
SOUND
Starting out in power boats then moving to sailboats changed me
drastically over the years. I like my vehicle without glass pack mufflers,
etc., and don't want to hear anything but the radio. On boats, any voyage is
much nicer when you DON"T HAVE TO YELL to have a conversation. I do decibel
tests on every boat survey (see testing methods page) and most levels are at
97dB to 115dB within that engine room, some are lots higher. Cabin spaces are
around 80dB and most could be a lot lower. The culprit is usually no or
incomplete sound insulation installed by the builder. Completely correctable
and easily done with a little time and the correct materials.
Soundproofing involves two concepts that
require two different materials with their own rating systems, barriers and
absorbers. The NRC number tells you how much sound energy is absorbed
(the higher the number, the more absorption), and the STC number rates the
amount of sound blocked in decibels (again, the higher the number, the greater the
sound absorption). For example, a brick wall has an STC in the 50s, whereas a
single-plate glass window's rating may be 30. Another figure to be aware of is
the product's flame-retardency rating. Do not install sound proofing materials
that are flammable, check that UL fire rating.
What is a NRC number? NRC, or Noise Reduction Coefficient, is the average sound
absorption of the four speech interference frequencies (250 Hertz, 500 Hertz,
1000 Hertz, And 2,000 Hertz). A material with an NRC of 0.95 absorbs
approximately 95% of the noise that strikes it. That is, it prevents sound from
reflecting off it.
|
Thickness measured
|
Noise Reduction Coefficient
|
|
1/4"
|
.20
|
|
3/8"
|
.30
|
|
1/2"
|
.40
|
|
3/4"
|
.50
|
|
1"
|
.50
|
The STC number, or
Sound Transmission Class, is a single number rating of a material's ability to
stop sound from going through it. It is used to rate doors, windows, walls,
ceilings, or any other partition between spaces. Generally speaking, the higher
the STC rating the greater the sound reduction. An STC value is a single number
rating used to characterize the sound insulating value of a partition (wall,
floor, or ceiling). A partition prevents sound from being transmitted from one
area to another. The higher the STC rating, the less sound will be transmitted
through the wall, floor, the higher the STC value of a floor/ceiling, the
better its ability to control impact sound transmission. A rating of 50 or
higher is considered acceptable.
56 and up=Excellent
45-55=Very Good 36-45=Good 26-35=Marginal 15-25=Poor As a reference, you can
hear normal speech through a wall with an STC of 25 At an STC of 42, loud
speech is audible as only a murmur.
If you were to make a mat of sound absorbing material thicker and use a
metal barrier inside it, it would be very effective in really stopping engine
noise coming through. So, if ordinary kitchen Reynolds Aluminum Foil is
sandwiched between the mats, (use contact cement), most of that noise will be
prevented from entering the cabin. A 2" minimum total thickness is recommended.
Another is a lead-backed material
originally developed for the military. It is expensive and heavy and I have
used it in U.S. Navy tour boats with great results.
Suggestion from the guy that has constant ear ringing! Make it easier on
yourself and the family, add the sound insulation. HOOK UP or A SANDWICH WOULD
BE NICE, sounds more professional WHEN YOU DON'T HAVE TO YELL.
Marine Engine Alarms
I am a big fan of alarms; it's the first thing on a survey that you
do not have to inspect with your eyes, magnifying glass, or meter! After
looking at the entire engine I can, I turn the key to on. Bells, buzzers, and
sirens tell me that if something happens while underway, at least there is
some system in place to let me know. Cruising, I even had a 12 volt counter
in the bilge pump system to let me know how many times the pump cycled, and it
had a piez buzzer with it (which I duct taped over after a knock down in the
Coral Sea).
There are a variety of systems available, from the $30 Cole
Hersey vibrating relay to the Aqua Alarm 5 sensor system for $300, and I am
sure many more. Use one and make it annoyingly loud. It would be
nice to hear differences whether it's the water temperature or the engine oil
but whatever you can afford. It could be the only thing between you having
to buy and install another impeller or rebuilding an engine, or worse. They all
seem to tie into the existing oil or water temperature sensors that come with
the engine for the gauges so it's not a complicated process.
Years ago lots of power boats had pyrometers in
the engines (a thermocouple that installed into the exhaust manifold with
a gauge) and some captains swore they could tell you if the prop had picked up
a piece of kelp by what the pyrometer temp was. They are still available and if
you look at your exhaust manifold you will probably find a square screw in plug
where they are installed. Some of the newer monitor systems attach into the
exhaust hose and monitor the quantity of water flow out the transom. Never
tried one of those, but if you are a gadget person, why not. Some of those
freighter and tankers you see on the horizon have a monitor system on each
cylinder of their engines that tell them the parameters of every engine stroke. The issue is, making sure your alarms
function if you have them and install something if you don't.
If you want to see something real different and maybe the future of
propulsion systems for recreational boats...
http://www.solomontechnologies.com/m_recreational.htm#multihull
Contact me,
Phone: 808-375-8260
Email:Bob@BoatSurveysHawaii.com
Robert J.
"Bob" Dupuis
Marine
Surveyor/Consultant
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