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Articles in this Issue:


A Message from our President

A lot has happened in the past year, so let me share a few of the highlights. First of all we now offer online schematic diagrams. All of the Volvo Penta engine and drive drawings are there along with the corresponding part numbers so you can identify your part and part number. Of course, we will e-mail or fax them to you if you prefer.

Second, Mercruiser parts are now available on the website, all 200,000 of them. Remember, if you don't find a part you are looking for, let us know and we can probably get it! We have thousands of expired and hard-to-find parts in our inventory. Our new web site, Mercruiser Central, has become a popular source for parts and Mercruiser information that you can't find anywhere else on the Internet. A full set of schematic diagrams for Mercuriser engines and drives reside there as well. We will continue to offer you the lowest prices on the web for marine engine parts, accessories and props. And with customer service that keeps you, our loyal customers, happy as proverbial clams. (Just see our attaboy page!)

I hope you enjoy our new articles, especially the one on Ethanol that Bob has written. We answer lots of marine engine and outdrive questions every day here at the shop, and this issue can affect everyone who has a gas engine. Finally, please take a moment to look at some our our prior articles of the Express because we wrote them to respond to questions your fellow boaters have asked. Certainly the article we did on winterization might come in handy right about now...

I look forward to hearing from you either by e-mail or on the phone when you have questions.

J. D. Neeson
President, Marine Parts Express
My email: jdneeson "at"
(yes, just put the @ in place of "at", don't you just hate those spammers?)


By Robert Van Brunt
Chief Petty Officer U.S.G.G. ret


Short description:
When the engine compartment becomes hot either by climate or idling, and you use ethanol-blend gasoline it can cause excessive vapors in your fuel line and starve the engine of fuel.  The engine can run poorly or stop and will not run until the fuel condenses.


Vapor Lock

Fuel containing 10% ethanol is called E10.  If you have ethanol in your gas, you run the risk of creating vapor lock because of excess vapors.

Ethanol “boils” at 87ºF (at normal atmospheric pressure) and turns from a liquid to a gaseous state.  By comparison, most automobiles have their fuel pump in the gas tank, so the whole system remains under pressure unlike boats whose fuel tanks are vented.  In a closed system, the higher pressure raises the flash point of the ethanol reducing the amount of vapor that is produced.  In addition, most automobile fuel lines are outside of the vehicle allowing them to stay cooler.

Since most boat fuel lines are in the enclosed space (sometimes even insulated) of the engine compartment, normal ventilation will not cool the fuel significantly enough to avoid the potential problems of vapor lock.  Furthermore, since the fuel pump in a boat is mounted on the engine (versus a car where the pump resides in the tank) the action of the pump can reduce pressure in the tank to below atmospheric pressure and further reduce the flash point.

Boat engineers are aware of this problem and are reducing the likelihood of this occurring by reducing the suction required by the fuel pump, minimizing hose fittings and bends, and including a quality anti-siphon valve.  In existing boats, fuel lines and filters should be kept as low in the boat as possible and tank vents should be cleaned and open.

Heat Soak

Most boats have “forced” ventilation.  Air moves through the engine compartment when the boat moves forward.  Heat soak happens after you have been at high RPM and then stop or drift on idle for a while.  Because of heat soak the engine compartment will rise to a point where the ethanol will boil


To prevent vapor lock (i.e. boiling ethanol):

  1. Make sure the engine compartment has adequate ventilation. 
  2. Relocate fuel lines to be low in the bilge.  (The bilge is cooler because it is in direct contact with the water.)
  3. Monitor the engine compartment temperature.
  4. Add (or turn on) engine room blowers.
  5. Keep the tank vent clean and unobstructed.



Ethanol is a solvent and can damage fiberglass tanks. It can dissolve old sludge in tanks which mixes with the gasoline and clogs filters.  This can cause the engine to run very poorly.

Since ethanol molecules bond with water molecules the fuel can be contaminated by water.  Fuel/water separators (filters) are supposed to separate out this water, but the amount of water trapped by the ethanol can quickly overwhelm the filter and allow water to pass through to the engine.  Moist air enters the fuel tank by the tank vent (remember automobiles do not have this problem due to their closed system designed to help reduce emissions).  Water can also settle to the bottom of the tank and cause the engine to run poorly and corrode fuel system components especially if the tank is not kept close to full.

E10 fuel is not as stable as past formulas.  Older formulations would stay “fresh” for about 6 months.  E10 can go stale in about 2 – 3 weeks.  This is not a problem for an automobile with a 15 gallon tank, but if you have a boat with a 250 gallon tank, watch out!


  1. The best way to keep water from the engine is to install a good water separator with a 10 micron filter to remove sludge and other contaminants.  It is also crucial to drain the filter and check it more frequently than you may have in the past.
  2. Volvo Penta recommends adding Sta-bil ™ to the fuel system.  This must be done with new fuel.  The Sta-bil will not treat stale fuel.

    Purchase 32 oz bottle
    Purchase 8 oz bottle

Express author Robert Van Brunt (Chief Petty Officer, U.S.C.G. ret) is a member of the American Boat and Yacht Council and a member of the International Association of Marine Investigators.


By Fred Sidelinger, Marine Engineer

There are a number of different stories on why the exhaust manifolds used on marine engines using Ford Blocks (Volvo Penta Part Number 3852347 or OMC part number 914898) seem to be on permanent back order.  One story is the foundry that makes these manifolds is having quality control issues.  Another one is that the foundry went out of business and a new foundry is going to begin to produce these shortly.  Yet another tale (and my favorite) is that the original foundry went out of business and the new foundry burnt down and lost all the molds.  What ever the truth is, these Ford manifolds are now just about impossible to get.

Marine Parts Express has come up with a solution for this problem and now offers a complete kit.  We have sold a number of these kits and have found they work well.  Because we are using OSCO aftermarket manifolds that were originally meant to replace Barr and Indmar manifolds for these Ford 302 and 351 blocks, it does mean that both the manifolds, risers, gaskets and hardware have to be replaced.  It is not possible to use your old existing risers with these new manifolds.  These new risers come down at a slightly steeper angle than the original, the outlet is approximately ½” lower, so the rubber exhaust hoses, included in the kit, may have to be cut a bit to fit. 

On our site there is a web page showing the pictures and part numbers of this kit. The price is around $670.


By J. D. Neeson, President

One of our customers, BoatSense (TM), has just finished Beta testing on a nifty little remote monitoring device for boat owners.  BoatSense (TM) felt existing monitoring systems were overly complex and expensive when all that was really needed was a way to notify owners what was happening on their boats.

The BSS 2.1 is a small completely sealed box (around the size of a pack of cigarettes) that monitors the water level and battery condition, as well as accepting three other inputs from other sensors or systems.  Once the BSS 2.1 receives an “event” signal, it sends a text message to the owner’s cell phone.  The owner’s cell phone becomes the keypad for the system.  It works with any cell phone service provider the owner might use.

Most catastrophic boat failures are related to either low battery or water level. While the basic functionality of this device is probably what will attract most people to it, what really appeals to me are those three additional inputs.  They could be wired to an anchor alarm, a security system, a fire monitoring system, or even an engine monitoring system.  A rented or borrowed boat could notify its owner if an engine runs at higher RPMs than it should or if it is has an overheating problem or needs oil.

BoatSense (TM) is also testing a system specifically designed for marinas.  It will allow them to monitor their customer’s moored boats (even transients can be provided a loaner unit) and send E-mail information to a PC in the office.

BoatSense (TM) offers an elegant and relatively inexpensive method for protecting your boat when you are not there.

(Our web site has further information describing this BoatSense (TM) product.

New at the Marine Parts Express Site:

Volvo Penta Engine Schematics

Mercruiser Engine and Outdrive Schematics


By J. D. Neeson, President
Marine Parts Express


Diesel engines, like everything else, have become increasing complicated over the recent years.  These improvements have made marine diesels much more efficient and more environmentally compliant as well as lighter and quieter.  (The EPA Tier I, II and III regulations have been the big impetuous for these newer designs.)  But this added sophistication has meant the newer engines are dependent on their computers to operate and require electronic diagnostic tools for most trouble shooting.  These new electronic tools are extremely accurate and give detailed reports on how the engine is operating.  They are also expensive and most people are unlikely, and in some cases not allowed, to purchase them.

However, the basic way that diesels operate hasn’t changed and by keeping in mind F.A.C. (Fuel, Air and Compression); it is still possible to analyze the exhaust smoke to help diagnose problems with your engine.

Black or Gray Smoke

Most diesel engines, even the new ones, create some smoke (black or white or both) when they first start up.  But if the smoke continues beyond the first few minutes, after the engine reaches operating temperature, there can be problems.

Solid black smoke is caused by unburned carbon from the diesel fuel while blackish gray smoke is a combination of this carbon and incompletely burned fuel.

So remembering F.A.C. lets start with FUEL related causes.

  1. Incorrect Fuel Grade or Contaminated Fuel.  Most people don’t have a choice when it comes to a fuel grade so grade problems are rare, but there has been a great increase in poor quality fuel.  When fuel prices go up if often seems the quality goes down.  So check the fuel from your tank and change the fuel filters often.
  2. Excessive Fuel or Irregular Fuel Distribution.  This is sometimes hard to determine, but it can be caused by:
    1. Improper rack adjustment.  This can be measured, but it is pretty rare.
    2. Improper Timing.  This requires a fair amount of knowledge and special tools.
  1. Faulty Injector Firing.  If the injectors haven’t been checked for a bit, it may be easier to have a mechanic remove these and Pop check them for you.  The newer engines have a common rail and operate under extreme high pressure so if a faulty injector is suspected you will have to call a certified marine mechanic.  On older engines with separate injector lines (mechanically driven fuel injection pump) you can check a suspect injector by disconnecting the fuel line while the engine is running and see the effect on the engine.  WARNING – Please don’t forget the pressure in the injector lines are in excess of 2000 pounds per square inch and can push fuel into your body.  People have lost fingers and arms not to mention blowing themselves up (especially easy on common rail diesels).  Don’t do this unless you are knowledgeable and have good insurance.
  2. Lugging or Overworking Engine.  This happens surprisingly often.  The engine is overloaded and sounds like it just can’t get up to speed.  It can be an incorrect propeller (over-sized or over-pitched) or something wrong with the transmission (stuck plates) or outdrive (grinding gears).  It can even be something as simple as a fouled propeller or substantial growth on the hull.

Next is AIR related causes.

  1. Insufficient Combustion Air.  Diesels require an amazing amount of air so you should check:
    1. Air openings in the engine room or external air vents.  We have seen people attempt to sound proof their engine and cause problems.  Sometimes during hull repainting the openings can be partially blocked.
    2. Intake air filter.  Remove and replace the intake filter.  This can be hard to see if it is clogged so it is easier to just replace it when in doubt.


  1. High Exhaust Back Pressure.  This is usually caused by some obstruction in the outgoing exhaust path.  Sometimes, on the older diesels with outdrives, the rubber flap in the exhaust pipe breaks loose and gets stuck across the opening causing both this problem and overheating.

And finally COMPRESSION related causes.

  1. Faulty Turbo-Charger.  If the turbo charger is not working properly, the engine doesn’t develop the sufficient air/fuel ratio and since the turbo allows the engine to create more power (why a turbo engine has more horsepower than a non-turbo one), the engine acts as if it is lugging.  Fortunately, most times turbo chargers either work or they don’t work.  You can check the turbo, when the engine is off, by removing the air filter and spinning the impeller.  The impeller should turn very easily and not wobble at all.  Incidentally this impeller is turning in excess of 20,000 RPM so there is any grinding, resistance or play then the turbo needs to be replaced.
  2. Incorrect Valve Clearance.  Incorrect valve clearance can also affect the compression stroke of the engine causing the engine to appear to be over working or under-powered.  Rarely does this happen quickly unless the head has been replaced.  This may be beyond the casual mechanic.


Blue Smoke

Blue smoke is almost always caused by excess lubrication oil somehow entering the cylinders.  The smoke, besides being blue, will have a burnt oil smell that is relatively easy to identify.   There are a number of causes of this:

  1. Worn or Broken Piston Rings.  When the condition gets bad enough the engine will begin to use up oil and can cause base pressure in the crankcase.  When the engine is running you can sometimes feel the pressure at the top of the dipstick hole.  The engine will have to be rebuilt.
  2. Scored Piston Liners.  This can cause the same symptoms as the bad piston rings and means the engine will have to be rebuilt.  It can be caused by contaminated fuel which is why it is so important to change fuel filters often.
  3. Faulty Turbo Charger Seals.  This is relatively rare, but sometimes the seals in the turbo charger fail.  Turbo chargers are oil cooled and if the seals fail the oil can be exhausted.  The only fix is to replace the turbo.
  4. Excessive Crank Case Pressure.  It is possible that the crank case filter can become clogged enough to allow the pressure in the crank case to rise.  Most times however, excessive base pressure (see #1 and #2) causes the filter to become clogged rather than the filter causing the pressure.  In any case you should replace this filter relatively often.

White Smoke

White smoke is caused by water vapor or unburned diesel fuel in the exhaust.  It reflects that there has been misfiring in the cylinder.  Often you can tell the difference by smelling the white smoke to see if the smoke has a diesel smell or not.  The typical causes of white smoke are:

  1. Head Gasket Leak.  This is usually accompanied by overheating issues and doesn’t happen all that often in most diesels unless there has been a catastrophic overheating problem.
  2. Cracked or warped Cylinder Heads.  This again is usually due to overheating and is usually not subtle.  The engine runs poorly, puts out white smoke and overheats.
  3. Faulty Injectors.  This means that an injector (or maybe more than one) is not firing properly.  It often gets worse overtime and sometimes causes the engine to start hard.  Rarely, but at times, it can cause some overheating.  The newer engines have a common rail and operate under extreme high pressure so if a faulty injector is suspected you will have to call a certified marine mechanic. On older engines with separate injector lines (mechanically driven fuel injection pump), you can check a suspect injector by disconnecting the fuel line while the engine is running and see the effect on the engine. WARNING – Please don’t forget the pressure in the injector lines are in excess of 2000 pounds per square inch and can push fuel into your body.  People have lost fingers and arms not to mention blowing themselves up (especially easy on common rail diesels).  Don’t do this unless you are knowledgeable and have good insurance.  It is probably a better idea to have the injectors removed and tested.  The injectors can be checked for their opening pressure (Pop tested), for leaking nozzles (contaminated fuel can do this), and for the correct spray pattern.  This requires special tools.
  4. Low Compression.  There are a number of reasons for low compression and it always makes sense for the compression to be checked (special tool again).  But whatever the cause, the reduced compression causes the fuel/air mixture to not fully burn and to allow the partially burnt fuel to exit with the exhaust.  Most times this does not cause overheating, but it can affect starting and the power of the engine.
Comments? Questions? Suggestions for topics in our next newsletter? Send them to Marine Parts Express is a division of Water Resouces, Inc., a privately held Maine Corporation.