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Old 12-27-2013, 03:34 PM   #1
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Yanmar 370

I am shopping for a boat and I recently saw an ad for a 2002 or 3 Mainship with a 370 HP Yanmar. The add said the owner had just replaced the injectors and turbo to the tune of 8K. The engine had less than 1100 hours on it.

I have never owned a diesel inboard and I hope some of you more knowledgeable folks will tell me. Is it common for such a low time engine to have these kind of problems? I was under the impression that Yanmars would run forever.

Thanks for any info.
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Old 12-27-2013, 04:53 PM   #2
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I am no diesel mechanic, but am a pretty good shade tree mechanic who does my own maintenance on my Yanmar 370. And I am an avid participant in the marine diesel forum boatdiesel.

The pros who hang out there say that injectors rarely need to be replaced but many mechanics do it anyway. They should last for thousands of hours.

Turbos also rarely fail in normal operation. But many boats are built with an exhaust system that allows seawater to back up and ruin them and sometimes the entire engine.

Modern, high output marine diesels do require more maintenance than simply changing the oil to keep them running well. The intercooler needs to be serviced periodically otherwise it can fail and flood the engine with seawater. The boat must be propped right otherwise the engine will overload.

If such an engine is maintained right, and it won't necessarily be cheap particularly if you have a mechanic do it, then these engines can last for thousands, maybe 10,000 hours.

And FWIW I wouldn't brag about spending $8,000 on a turbo and injectors. Other than the obvious concern that the exhaust system is faulty and that the injectors were replaced needlessly, it is way too much money even at $100/hr mechanics rates.

PM me if you find a boat that you are serious about and I will try to help with the engine.

David
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Old 12-28-2013, 06:45 PM   #3
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I really appreciate that. Thank you. Would you say a normal purchase survey would catch the potential exhaust problem you mentioned or is that the what I need an engine survey for?
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Old 12-28-2013, 08:38 PM   #4
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If you compare 8K for repairs, to max <1K for a mechanical surveyor, it`s no contest.
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Old 12-28-2013, 08:43 PM   #5
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Pluto:

Most hull surveyors have no clue about exhaust system design. Heck, I'll bet most engine surveyors don't either. It is an issue that affects maybe one or two out of a hundred customers of a badly designed exhaust system. But when it does....

PM me your email address and I will send you a prepurchase survey checklist that you can do yourself.

David
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Old 12-29-2013, 06:17 AM   #6
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Sounds like a 1100 hours of low low power operation might have gunked the turbo to useless ,.

The injectors should have been fine , unless the fuel filtration is very poor.

Turbos can be cleaned at very modest cost.
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Old 12-29-2013, 08:02 AM   #7
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Mainship corp also has a history of poor or marginal exhaust system designs in thier boats as well as a history of overloading the engines.
So listen to David and get that checked out.
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Old 12-29-2013, 08:43 AM   #8
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Turbos also rarely fail in normal operation. But many boats are built with an exhaust system that allows seawater to back up and ruin them
Dave

Aren't some Yanmar powered Mainships inadvertently built with exhaust runs that are prone to water backing into the turbo and flooding #6 cylinder? On the OP's vessel in question that seems a possibility given the turbo replacement.

For the OP, I'd suggest some extra diligence on assessing the exhaust run.

Oops, I see Jay says the same.
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Old 12-29-2013, 12:25 PM   #9
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Sunchaser:

You are absolutely correct. The pic on the left (or top) is of my Mainship Pilot 34 before I extended the dry riser. The spill over point was just 8" above the waterline. Many owners report no problems, but....

The pic on the right (or below) shows the new extended dry riser- the vertical shiny piece behind the support strut. The exhaust elbow is now pointed down so it will drain dry when shutdown and not into the turbo when it fails internally.

David
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Old 12-29-2013, 07:17 PM   #10
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call Roland at Sun Power Diesel in Ft. Lauderdale (Harbor Town in Dania to be exact) and ask him what he thinks about Yanmars. This super experienced mechanic isn't shy about giving his opinions on the engines they sell and service.
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Old 01-01-2014, 08:43 AM   #11
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This may be a stupid question, but why not just install a flapper valve or check valve of some sort to prevent wave action pushing water up the exhaust?
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Old 01-01-2014, 11:41 AM   #12
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but why not just install a flapper valve or check valve of some sort to prevent wave action pushing water up the exhaust?

They all fail eventually.

A proper exhaust is a better option.
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Old 01-01-2014, 11:41 AM   #13
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This may be a stupid question, but why not just install a flapper valve or check valve of some sort to prevent wave action pushing water up the exhaust?
Because of the low profile, I have two of these on the dual exhaust for the 3208 on my Blackfin. It has trolled in some very nasty seas.

marine exhaust flapper covers - Yahoo Search Results
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Old 01-02-2014, 05:08 AM   #14
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It has trolled in some very nasty seas

Trolling , underway , the engine is operating , no problem clearing the exhaust.

Tied to a slip , engine secured with a 1 or 2 ft wave from astern can be a problem.
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