What’s Wrong with the Diesel?

By Carolyn Shearlock © 2015 • all rights reserved

Whats wrong

I’ve written before about how our diesel died on the way south from Ft. Myers and how we’re having to rebuild the engine (read about the trip here; the decision to rebuild the engine here). I’ve had a lot of questions about what we’ve found in the course of the rebuild and what the problem seems to be. In short, what caused this?

A few background facts:

  • We bought the boat last April with 350 hours on the engine, a Westerbeke 30B.
  • The boat had been repowered in 2010 by a previous owner — not the one we bought the boat from. We do not know why it was repowered at that time, when the boat was just 11 years old.
  • The survey indicated no problems with the engine. Due to the young age and low hours on the engine, we did not have a separate engine survey.

Our trip before the engine died:

  • When we put the boat in the water after being in storage for the summer, the engine fired right up with no problem.
  • The engine ran well except for a couple of times when we lost RPMs briefly — we thought this was due to bad fuel and changed the fuel filters.
  • We motored about 40 hours over 8 days.
  • The engine made no strange sounds and was not smoking.
  • The engine did not overheat and oil pressure was good.
  • The engine was running just 12 hours before it refused to start.

A compression test showed very low compression in all three cylinders (it should be 398 psi in each; it was 200 in one and just under 100 in the other two). What we’ve learned since:

  • There is absolutely no sign of salt water intrusion anywhere from the exhaust system.
  • Two injectors were bad.
  • All valves were carbonned up badly and not seating (closing) properly.
  • All piston rings were stuck badly — carbon, not rust.
  • No noticeable wear on cylinder walls.
  • The engine is very clean.

We’ve had three different mechanics look at the engine and consulted with several others via phone and email.

The consensus is that this shouldn’t happen to an engine this new and with this few hours.

But it has and so the second consensus is that the most logical explanation is that the injectors being bad put a lot of extra fuel in the cylinders, which caused the valves and rings to carbon up. Apparently this had been going on for some time, and the day the engine wouldn’t start was just a case of “the last straw.”

Yes, it seems more likely that the engine just wouldn’t have started after being stored for the summer if it was carbonned up. And that the bad injectors would have made it run rough before it died. But it ran well just 12 hours before it wouldn’t start. And that’s another reason why everyone is so puzzled.

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Comments

  1. Following with interest as we also have a Westerbeke 30B.

  2. Have someone come polish the fuel and the tank also. That’s your root cause

  3. This is a long shot but you migt want to get ur fuel tested to see if it was contaminatd with something like sugar. Sugar will cause huge levels of carbon build up in ur combustion chamber

  4. Suzan Christensen says:

    you might want to do an oil analysis (costs like $30) to check for contaminants like excess fuel. Some fuel wash down is normal but lots would lead you back to injector or fuel delivery problem.
    This suggestion is from my husband– we had a Westerbeke in our Allied Seawind II before we changed to BetaMarine. Good luck!

  5. A bad thermostat ( stuck open) will not allow the engine to reach full operating temperature which will also cause excessive carbon build-up.

  6. So frustrating, sorry Carolyn. Hoping you’re soon back out on the water.

  7. Was that 350 hr motor rebuilt or was it a replacement for the existing? Is it possible it wasn’t a true 350 hr motor???

  8. Dallas Shaw

  9. Not really enough info, but the compression issue is the key. The carbon buildup compounds the problem, but i believe it is a side effect of poor combustion due to low compression. I would be looking for a valve timing issue.

  10. Maybe this man has an answer. http://www.soundmarinediesel.com/index.html Make sure exhaust is able to freely scavenge – ( my psychic guess )

  11. I would look seriously at the exhaust system. I’ve seen this sort of problem many times before and it has been due to incorrect back pressure in the exhaust. Make sure your setup is the same as other Gemini owners and not some one off setup that occurred during the repower. Also have you tried going back to the firm which did the repower? Good luck and God speed!

  12. Mike Miles says:

    350 hours on an engine is only just run in. I am surprised that there was not a tell tail sign in the exhaust. Black exhaust – too much fuel, blue- too much oil past the rings or valve stems or wrong timing, white – water leaking into the cylinder.
    An analysis of the fuel looks to be a good idea. Don’t want to have the same problem after the next 350 hours!

  13. Hello, my partner alerted me to this issue. My advice is the last thing people like to hear – this issue is pretty clearly operator error. Very likely the previous owners of the boat/engine were driving very sedately, such as putting along at 2 knots quietly. This is extremely bad for small high speed diesel engines. They need to operate within their designed rev range, which will be outlined in the operators manual. Make sure you don’t spend hours just idling the engine in gear or in neutral, this will surely produce the exact signs and symtoms you have described.

  14. The last step of the butterfly video is exactly what we do — but we leave the tail longer to use to tie it to something else, when necessary.

    The butterfly looks great for small stuff, but thicker, longer lines , doubled up would not fit in my hand!

  15. Ken Arnold says:

    1, Get rid of all the old Fuel and put fresh Fuel in. Find some “Howes Fuel treatment” if You can find it and put that in. “PS” (Power Service) also is good stuff if you can’t find Howes.

    2, Check the Air Intake piping, filter/s, especially any Rubber Hoses that can suck down and cut Air Flow

    3, Check the Return Fuel line for Kinks/Restrictions. That causes over fueling and lots of Carbon / Black Smoke

  16. Ebb Tide says:

    Carolyn, recently we were in boot key harbor.
    John Strickland (happy cat) replaced the tension damper plate and rear main seal while we were on a morning ball.
    Did John rebuild your engine?
    Alex diagnosed a electrical problem on our engine. This is after several “experts” failed to find the problem.
    Both these men are a rare find.
    Ebb
    Katie Rose #966 MC 105

  17. I had a Westerbeke 21 in my 30′ sail boat that failed at 850 hours which was almost immediately after I bought the boat. It had the same internal condition you describe, carboned up rings not sealing and it had “the worst looking head” my mechanic ever saw. Namely highly carboned valves. I did a rebuild with the engine still in the boat. Sent the head to a shop for rebuild and rehoned the cylinders. Put in new rings and the engine purred for 1200 more hours till I sold the boat.

    The cause of the problem is too light a load while running for extended time. Either the PO ran the engine at idle to charge the batteries or what I expect was the real cause, a two blade prop with insufficient pitch. I changed out to a 3 blade. The engine should just make or be slightly short of WOT under load full throttle. If it makes WOT under load easily your underpitched. If it puts out black smoke before WOT then you over pitched. A light cat will push easily thru the water so its important to get the prop right to keep the engine loaded. A good prop shop like Frank & Jimmy’s in Fort Lauderdale can help out.

    Any extended running should be at 80% of WOT to keep the engine loaded. For your Westerbeke WOT is about 3200 rpm making cruising at 2500 to 2600 about right. Also IMPORTANT upgrade the multipart exhaust manifold to a single cast type.

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