Do I Have the World's Only 3 Cylinder Gasoline Engine?

Background

My boat is 69 years old. I didn't trust the engine so in 2012 I decided to have it rebuilt as I wanted something I didn't have to worry about. I can't say I achieved that goal. The most persistent problem was the exhaust valve sticking on the aft-most #1 cylinder. Very occasionally at first but toward the end it became virtually unusable. One of the issues is that when the exhaust valve sticks the cylinder sucks water out of the wet exhaust. Does it stick because of the water or does it get water because it sticks? I don't know but I do know that over the years I tried everything anyone could think of to keep it from sticking. I replaced the water lift muffler, I replaced the valve, I rerouted the exhaust. I tried Marvel Mystery Oil (MMO) in the oil and tried pouring a little into the cylinder each time I came back to the slip. No matter what I did, the problem just kept getting worse. The final straw was water in the oil typical of a blown head gasket but upon removing the head the gasket was fine.

New Engine Time?

Finally I had enough. I decided to repower with a Yanmar Diesel. I got a quote. It was expensive but I wanted a reliable engine. Before sending the deposit I wanted to make sure it would fit. I took careful measurements and sketched the cockpit engine relationship. You can see from the sketch on the right that it would not fit. Now what?

The Problem

I considered an electric conversion. But that is probably a year-long DIY project and at 78 years old and a life's goal of sailing until I am 80 that didn't seem like a good plan. I certainly hope I can exceed that goal but still. I came to the conclusion that I needed to give one more try to fix my bad cylinder. When I replaced the valve in 2022, I did not do a good job. I used lapping compound instead of grinding the valve seat. I didn't know any better and it seemed OK but when I was done the compression was still low, not bad but not up to the other cylinders. Over the intervening years I did some research and found that Neway and Regis made the tools I would need to grind the seats and condition the valve guide. I even found a NOS exhaust valve on eBay. Perfect. That should give me what I need to do the job.

Getting the Valves Out

A Gray Marine engine is what they call an L head engine and the valves are in the block. I have rebuilt many engines over the years but I always took the head to a machine shop and they would grind the valves. In this case, I could not even get anyone to do the work because nobody works on gas marine engines any more. I was aware I didn't know what I was doing and that I had to do it myself but with a proper valve guide reamer and a set of Neway cutters, I should be able to do a good job, now it was time to take the engine apart.

Most things come apart easily but getting the valve springs out is very difficult. I found a YouTube video that recommended using long reach 45 degree bent long nose pliers. That worked where using a valve spring compressor did not. The compressor does work well for installing the springs. The intake valve spring came out easily but the exhaust spring broke and I had to cut the remainder of the spring with a Dremel and half a dozen grinding wheels. Some people say that is the best way to remove the springs anyway so no harm no foul - they are cheap. The intake valve came out easily but the exhaust valve was super stuck. It took a week of soaking with PB Blaster to be able to remove the offending exhaust valve using a surprising amount of force. To my surprise it was just gunk keeping the valve from coming out. It wasn't bent or otherwise deformed.

Seeing the Damage

With the valves out I was able to see what I had to deal with and what I saw was not pretty. The exhaust seat was in terrible condition. It needed to be replaced but that was impossible with the engine in the boat. But I had a backup plan.

The 3 Cylinder Idea

In a phone call a few months ago, the mechanic that did my rebuild said "why don't you just run it on 3 cylinders". That sounded crazy and I was not even sure he was serious because when the valve sticks the cylinder sucks in water and the water gets in the oil. But I kept thinking of that comment and did some research. Google: Can I run my engine on 3 cylinders? Reddit had a thread. No, no way. No how, no can do. said Thisisall_new2me2 and others. But Lxifyby said he drove his Civic another 30k miles on just 3 cylinders. Plus, I had just watched one of my favorite YouTube channels, SuperFastMat. He had disabled two cylinders on his motorcycle engine powered land speed car to set a world record for the 500cc class at 207MPH. He just removed the lifters so the valves would stay shut and disconnected the injectors. If he can do it, so can I.

How I Did It

At this point I had two options. I could try to grind my trashed valve seat and run on 4 cylinders. Or I could disable that cylinder and run on 3. There was no guarantee that staying with 4 cylinders would work out any better than it did last time. Converting to 3 would definitely solve the stuck valve issue and I could always take it apart and go back to 4 cylinders if it didn't work out. So that is what I did.

It was not possible to remove the lifters but removing just the adjuster bolts gave me enough clearance so that the valves would not open. I installed the valves with a bit of silicone sealant on the valve seats to make sure there would not be any leakage. I installed new springs and put the head back on. I initially just left the spark plug in but there was a little water condensing on the spark plug. It did not seem like a good idea to run the engine that way. Leaving the plug out was quite loud so I threaded an air compressor exhaust filter into the shell of an old spark plug that I drilled out and tapped to 1/4 NPT. That would also keep critters and debris out and allow the cylinder to breathe so that moisture would not accumulate. I connected a resistive core spark plug wire from the #1 distributor output to a stud on the transmission that was close to the diameter of a spark plug tip. This load prevents any arcing in the coil or distributor. What was left now was a simple trial.

The Test Sail

Our first sea trial was a short one. The engine ran well under load but idled poorly. It would stall coming back into the slip. Closing the idle mixture almost all the way fixed it. I don't know why that was the case, but after that adjustment the idle was stable and we were ready for a real test.

We didn't plan to test the engine quite like we did on our second test. We sailed out just over two miles. On the way back we were sailing at 2.8 knots through the water but only 0.5 knots over land and in the wrong direction because the wind was coming straight from the marina. On top of that, it was a King Tide. The current was strong, and we had a limited window before the water level in the marina dropped. To stay on the safe side, our goal was to be back by 2:30, which would give us a 30-minute margin.

We dropped the sails and started the engine. It held 4.8 knots through the water, 2.3 knots over land, pushing against the current the whole way. It took almost exactly an hour. We made it back on time. The engine in 3 cylinder mode ran perfectly. Smooth under power, no misfires, idled down without stalling when we got to the dock. That was as hard as I have ever run the engine for that long and the oil pressure proved it. It was down to 9 PSI at idle. At 700 RPM it was still above the 10 psi per 1000 RPM rule but about as low as I have seen it. For comparison, on a normal sail I have 17psi at 700RPM after the sail. It was a stress test and it passed. It did exactly what I needed it to do. I could have gone faster, but I didn't want to push it any harder.

Summary

All things considered, I am pleased with the engine I have now. Would I have preferred having all four cylinders? Of course, as long as the #1 cylinder didn't suck water and its valve didn't stick. My decision to go with 3 cylinders rather than grind what was left of the valve seats came down to why do I need an engine in my sailboat. It is, after all, a sailboat and not a power boat. I need an engine to get out of the marina and to return. My marina entrance is dead into the wind making some kind of motor or engine necessary. I knew from times when the valve was stuck open that 3 cylinders had enough power to get into the marina. I also knew that disabling the #1 cylinder was going to eliminate having that valve stick. But I also need an engine for the rare times when the wind dies, I need to get back to the marina, and there is a strong current. Times like the test sail described above. Times when an electric would be put to a test it may not pass. And of course, I knew a Diesel would not fit.

I do worry about what might go wrong. I worry that the #2 valve might start sticking. But the #1 valve is in an especially vulnerable position. It is adjacent to the exhaust and closest to where the water injection happens. It is also closest to where the raw water cooling comes into the engine so it ran the coldest of any cylinder. The #1 exhaust valve obviously cannot stick open now but I worry it might still leak and suck in water. I worry that the Silicone might not seal the poor valve seat enough. But having the cylinder vented should reduce any sucking force and expel any water that does get in.

While I do have some things I can worry about, these worries are coming from me and not from the engine which is exceeding my expectations. The engine sounds different but it runs smooth without any vibration. I no longer have to take the plug out and make sure the valve will start form the closed position. I no longer have to pour MMO in the cylinder. It is actually running much smoother. So far I think this was the right decision. Plus it is reversible if I am wrong. And I know from Reddit and SuperFastMat that it is not a crazy idea.