Engine Rebuild

It started with a small leak, actually three small leaks. The first one I noticed was the leaking raw water pump. I decided to wait till we got to Antigua to fix it in case I needed access to a Yanmar dealer. Then I noticed a small fuel leak on the fuel filter. While running the engine after fixing both leaks, I noticed that there was also a small oil leak at the breather tube cap and, more ominously, exhaust fumes in the engine compartment. I replaced the breather cap gasket and solved both problems but I was suspicious about the exhaust leak so I removed the breather tube and found exhaust gases rushing out of the valve cover. In addition the engine started stalling when put into gear. I had a compression test done in Falmouth Harbour and discovered that the #3 cylinder had low compression. Hoping it was only a stuck ring, I tried soaking the cylinder with wd-40 and pb-blaster unsuccessfully. Because our son and his wife were coming to Antigua, we decided to wait on any repairs and learned how to maneuver the boat using only the port engine. After our son and daughter-in-law left, we pulled the head to see if it was cracked. It looked fine but wd-40 quickly ran past the rings on #3 but not the other cylinders, so we knew we had a ring problem. I bought a new piston and rings, thinking that I could replace the one piston, probably at the marina in St. Lucia. However a second problem, the loss of our refrigerator, prompted a visit to Sint Maarten instead because of the wealth of support services available there. That was a fortunate decision.
We removed the starter, alternator, heat exchanger and head (to reduce weight). Here the engine is separated from the saildrive.



Using a block and tackle jockeyed the engine into the cockpit.
We removed the cockpit table and arranged a working area there using old towels and the stainless steel base of a defunct solar panel.




This took three hoists, first with the boom to the cockpit coaming. Then to the cockpit seat and finally the cockpit floor using the bimini as a hoisting point. When we finally were able to remove the piston, we discovered that the top compression ring was broken in three and the second compression ring was shattered.



The piston itself was fractured between the rings.

Luckily Simpson Bay Diesel, the local Yanmar dealer, was close by to the Marina where we were staying and they said that the engine needed to be bored and sleeved. Here you can see the scratches made by the broken rings.



Fortunately, there was a good machine shop on the French side called Mendall. However this meant that we had to strip the engine down to the block. Since this required a special deep well socket which I did not have, we brought the engine (using our grocery cart) to Simpson Bay Diesel where they were able to remove the governor nut. We dinghied the stripped down block over to the French side after Bastille day and they were able to bore and sleeve in one day.
Here is what the cylinder looked like after the sleeve was inserted.


We slowly put the engine back together, working out a detailed plan of what needed to be done, what tools were needed, torque specifications, etc. We were given a respite on Sunday due to the rain of the system that eventually become Bonnie. Two weeks after we started, we were finished with no extra parts and only three missing parts (which we later discovered after improvising replacements). The engine started better than ever and we decided to take a mini cruise to St. Barts to test the engine. So far all is working well.

Neither Simpson Bay Diesel nor Mendall had ever seen a piston with a ring as shattered as ours and they both suspected that it occurred during manufacturing or assembly. Since we had almost 2200 hours on the engine, it took quite a long time to show up. However, that engine had a persistent leak from the rear main seal (which was half out of the end cap when we disassembled the engine) and more curiously, the timing cover gasket blew out at the bottom and had to be replaced three years ago. So we may have always had a ring blow by problem that suddenly got worse in Antigua. Getting the engine out of the engine compartment is relatively easy and working on the engine in the cockpit worked out quite well. I took pictures of everything before I started and during the disassembly which proved invaluable during re-assembly. We studied that engine manual each morning before we started and planned each day in detail. I also used the parts manual to make sure we replaced all relevant gaskets, o-rings and copper washers. Having easy access to a Yanmar dealer and good machine shops was crucial to the successful resolution of our problem. Besides the sleeving, we needed to have the crankshaft bearings pressed in.

Here Pam is cleaning the engine compartment which is much easier with the engine removed.