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Old 07-22-2015, 01:08 PM   #1
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Yanmar 6LYA 370 hp in Mainship390

Does anybody know if the Yanmar 6LYA 370 hp has any issues in the Mainship 390 single engine.Boat is 2003. Thanks in advance Steve

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Old 07-22-2015, 01:42 PM   #2
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Originally Posted by sjhoman View Post
Does anybody know if the Yanmar 6LYA 370 hp has any issues in the Mainship 390 single engine.Boat is 2003. Thanks in advance Steve
Don't know about the 390, but I had a 2004 Pilot 34 with that engine. It was a strong performer, and gave zero problems. I probably ran it harder that you normally would in a 390. It got 2 mpg at 16 knots in the Pilot. That was running about 2800 rpm.

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Old 07-22-2015, 01:45 PM   #3
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Although I don't own one with this engine, I have been a member of the Mainship owner's group in Yahoo since its inception and rarely hear of any major issue. I know of several with this engine in that and other models and they seem to be fine. As in any boat, maintenance and treatment of the particular boat is the key.
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Old 07-22-2015, 01:56 PM   #4
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I owned a 2006 Mainship 34T with that engine and now have a Pilot 34 with the same engine. I do all of my own maintenance, but am not a diesel mechanic by any means.

The real issue in so far as a specific boat installation is usually the exhaust system design. I have not heard of any issues with this on the 390.

The Yanmar 6LY 370 hp is a very solid engine.

Make sure that you use the approved Dexcool antifreeze. Regular, high silicate antifreeze can damage the aluminum exhaust manifold.

The raw water impeller is a chore to get to and most owners remove the pump to change the impeller but that job isn't easy either due to limited access.

The air cooler needs routine servicing, at least every five years and that includes disassembly, cleaning, new O-rings, lots of grease, reassembly and pressure testing.

Prop it to reach 3.400 rpm and cruise at 2,800 or less, maintain it right and you will have a happy engine that will last many thousands of hours.

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