Yanmar Engine Self-Repair: Part 2

Here are some details of my Yanmar Engine Self-Repair....
There is a German phrase that is straight to the point; "Wer rastet, der rostet" meaning "He who rests, will rust". I know that with my motorcycles, they are either up hanging from the garage rafters or the frames are up on blocks so my brother can turn over the engines and drive trains every month while they wait patiently for my return. Right: Injector Hole #3.

With my engine, I did NOT do this! When I returned to my favorite anchorage after the Hurricane 'Bill' adventure in the mangroves, I should have run my Yanmar engine a few minutes each week. I did NOT turn it on for 5 weeks and then it seized! Left: Water in #3 Piston.

After the Yanmar technician showed me the sea water in the #3 cylinder, he said it could cost up to $8000 to get it repaired at their Yanmar facility, and would take 3 - 4 weeks. I bought the parts and the Shop Manual, and strarted to 'Do-It-Myself'. First I had to take off all connections - electrical and plumbing.

The Yanmar 4JH4 owner's manual says that after running the engine for prolonged periods at low rpm, before shutting the engine down, you should rev up the engine 5 times to full power and then shut the engine down, to remove carbon build-up in the turbo etc. In my opinion, you still need to let the engine cool down at idle speed a few minutes before you bring it to a stop. My mistake was revving the engine to 2800 or 3000 RPMs for a few seconds five times and then just shutting the engine down. My friend and retired trucker diesel mechanic James, who helped me with the over-haul said you should ALWAYS let the engine idle for 5 or even 10 minutes after running it for a prolonged period, especially the new high speed turbo and ultra high compression 4 valve engines. I did NOT do this, with drastic results.

I learned from my father years ago that when tearing down an engine, you pull off the first things and put each item and its nuts or bolts in a separate container and at the back or end of the work bench, or in this case, a towel lined aft bunk floor. Then you just work clean and organized, labeling or numbering each item with masking tape and a magic marker.

Then I had to lift out the engine from the bilge and onto boards across the sole (floor) to get the engine up to a workable height.
I used a large diameter pipe across the top of the companion way entrance and a borrowed chain hoist.

The engine would not turn over, even with a big leverage bar on the crank-pulley nut. The piston was seized and was soaked in 'Corrosion-X' overnight. But it needed to be drilled and chiseled out.

After taking turns with my friend James at whacking at that piston, then drilling some holes and whacking again, we needed a full day to get that seized piston to finally come loose and pieces removed. I bought a special 'honing' devise to attach to my power drill and we cleaned up and polished the inside cylinder wall according to the Yanmar 'Shop Manual'.

The Yanmar distributor for SE USA, Mastery Engines, was very helpful and especially their service manager, Doug Dykens. He sent me "Everything You Need for an Engine Re-build" including all new seals and gaskets, a new piston and rings, all the little parts for the fuel injectors, and even a special tube of adhesive for the pan gasket. I kept the 'old' piston just as a reminder to check ALL hoses and fittings before a voyage.

Finally, after 7 continuous days of 8 -10 hours work, I was ready to turn her over. James was at the engine and I was at the wheel with the starting key. First tick and she purred like a kitten! Elation and a sense of accomplishment.

After 4 hours of idle speed, I changed the oil and filter. It was a bit dirty and had some diesel fuel mixed in. At ten hours and up to 1800 rpm sailing down to St. thomas and back, I change the oil and filter AGAIN, but it was perfectly clean!

Now, after 25 hours, I hired one of the off-duty Yanmar service technicians to come over to 'WanderLust 3' and check things out and inspect my 're-built' engine, just to make sure I didn't mess anything up. He removed the valve cover and with a feeler gauge checked the tolerances of the valves. They were good. Then he tightened the head bolts with a torque wrench, they were also good. Then a compression check, everything was broken in and running great with 25 hours on the rebuilt engine and two (2) oil and filter changes.

He was slightly impressed that everything seemed to be working perfectly. Then he went to the new Anti-Siphon Valve and also checked the old one. Sure enough the old one was corroded around the rubber flap AND the pressure release tube. This made him think to follow the end of that old tube, re-installed on the new siphon valve. He discovered that the open end, that is supposed to drain and relieve the sea water pressure, was way too long and run under the engine in a cavity that was not visible. When he pulled out the open end of the hose, it was completely CLOGGED with old oil and other debris. That means that eventually the new Anti-Siphon Valve would have FAILED again because the relief tube end was still clogged.

He simply cut that tube, and the parallel one for the generator, about 2 inches above the bilge so it would simply drain down into the bilge AND was also VISIBLE for inspection.

I can only recommend that everyone check the COMPLETE ANTI-SIPHON VALE ASSEMBLY. That maintainance check is NOT in my Hunter Owner's manual nor in the Yanmar book, but it IS in the one essential book I carry from NIGEL Calder, Boat Owner's Mechanical and Electrical Handbook. He devotes five (5) pages (377 -382) to just the subject of "Siphon Breaks". Read it!

Mike Harker
s/v Wanderlust 3

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