Yanmar Engine Self-Repair: Part 1

How can an $80 part cause $8,000 engine damage?

After returning to my favorite spot in the Simpson Bay Lagoon after seeking refuge in the Mullet Pond Mangroves after the only Hurricane (Bill) to be near St. Martin this summer, I did not run the main Yanmar engine for over 7 weeks. That in itself was wrong, I should have run the engine, even for just a few minutes, at least once a week. But with 3 large solar panels and an Air-X wind generator, I only needed to charge my house batteries and make water for about 3 hours a week using the 12 Kw generator.

What I did not know was that the 'Anti-Siphon Valve' at the top of the sea water outlet to cool the intercooler on the Yanmar was corroded and the little flap did not close, allowing sea water back down the hose and into the exhaust, including back through the turbo, exhaust manifold and finally into the open exhaust valve of # 3 cylinder.

The starter would not turn over the engine, so I tried with a 14mm socket to turn the shaft nut at the alternator belt, but no luck. I went over to the Yanmar service facility and the mechanic came out to the boat and took off some hoses and the valve cover to show me how #3 cylinder was filled with sea water.

After e-mailing the Yanmar distributor in Florida, "not a Yanmar part" and the boat manufacturer Hunter, "out of warranty and a maintenance problem not covered under warranty anyway", I asked the service office for a quote. $5000 in cash, in advance, just to have a look at the damage! This would include towing over to their facility, a crane to haul out the engine and 3 - 4 weeks in the shop. If the turbo was damaged and the head and valves needed work the total could be above $8000!!!!

I grew up in Southern California with my Dad and two uncles racing and tuning their race boats. I've seen engines apart at the launch ramp, on an 'All-Night Saturday Night" engine repair before the big race Sunday and enough garage mechanics to attempt the engine over-haul myself. I had the Yanmar 4JH4 HTE service manual and I got Yanmar in Florida to send me all the parts they think I would need, including a new piston and rings, injector tips and all the seals and gaskets for a complete overhaul, and a 'Wish You Luck!".

After getting a steel bar across the companion way and the loan of a small chain hoist, I got the engine up and out of the 'bilge' area and on to boards across the boat's sole. With the stairs removed, I had to enter through the forward hatch. I also got the expertise of a real diesel mechanic, a retired local living on his sailboat for years, JAMES. He has worked on 'many a diesel' including old boat engines and trucks, but never a turbo charged, 4 valve per cylinder modern sailboat engine.

After exactly 1 week we put the hoses back on the engine and fired her back up. She runs perfectly. The turbo was professionally opened and cleaned including new seals and bearings and the head and valves were cleaned and polished. The cylinder wall was honed and polished using a special tool aboard the boat.

For around $800 in parts and about 80 man-hours, we got the engine apart, repaired and back working again. I do NOT recommend that anyone do the same without professional diesel service technicians, but when you are in a desperate situation and need to 'Fix-it-Yourself', it can be done.

I have over 24 hours on the overhauled engine sailing down to St. Thomas and back, I changed the oil and filters twice and the coolant replace a second time and everything works as good as, or, as it seems, better than new.

In Part 2, I'll talk about specific steps during my Yanmar Engine Self-Repair.

Mike Harker
s/v Wanderlust 3

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