Engine Maintenance

Our engine is a single cylinder Yanmar 1GM10. It’s horrible and unreliable despite having less than 500 hours on it. While we probably won’t keep this engine, the simple nature and constant issues have given us many opportunities to work with and learn about diesel engines. Also with it’s low horse power, it’s been a good proxy for the continuous power we would get out of an electric engine if we decide to install that instead. Having said all that, it is what we have for the next few years, and below are some of the problems we’ve run into and thoughts on engine care.

Soot Build Up

The main issue with our engine, is that soot builds up and clogs the system. We have theories that this relates to the injection timing, but it is a difficult thing to test unless running for dozens of hours continuously. The failures this has caused have manifested themselves in many different ways, with the worst one caused by a clogged exhaust elbow. A clogged exhaust elbow is a common failure of the 1GM10, and in our case it caused the entire engine to overheat and loose compression right next to a rock break. That was our worst failure, and promoted us to take apart and rebuild the top half of the engine just a month after purchasing the boat.

Since then, we’ve converted to an after market stainless steel exhaust elbow, and pull the exhaust elbow at least once a year. We carry spare exhaust elbow gaskets for this, but often don’t find they need to be refitted and only replace when worn. Since our catastrophic elbow failure, the exhaust elbow has never been clogged again, despite not changing the injection timing.

Another issue we’ve had with soot build up, is on the injector itself. After motoring continuously for dozens of hours on another occasion, white and then black smoke began to come out of the exhaust. The engine was unable to rev higher and began to lose compression. To try and clear out some soot, we reversed hard a few times, and this returned the smoke to just white and allowed us to motor another 4 or 5 hours into port. After arriving in port, we pulled the exhaust elbow to find it completely fine. This pointed to the injector itself being clogged, and after running Diesel Kleen through the secondary fuel filter, everything returned to normal. We now always keep Diesel Kleen on hand for emergencies.

Fuel Quality

If a diesel engine isn’t running correctly, normally fuel is the culprit. The common knowledge is to always keep the tank full, so that condensation will not build up and introduce water and growth into the tank. For us however, this has not turned out to be the case. Even leaving the tank half full for 9 months twice (hard to use much fuel day sailing), we’ve never had any growth. Both times we’ve pumped out all the fuel from our tank to polish it through a Racor filter and an electric fuel transfer pump. Each time it has been completely fine and free of water and growth. All we add is biocide when first filling up the tank.

Despite our good luck, this is not a good practice, and we now try to keep the tank at least 3/4ths full or more. Regardless, we will eventually run into growth, and we’ve tried out a few solutions in case we run into this. Since our tank is only 18 gallons, we at first removed it and put chain inside and shook it around to knock away loose growth. We then used a borescope to check the growth (which there was none). This was a very time consuming process however, and didn’t feel like it would remove much growth. If we ever need to clean the inside of the tank again, we plan to add an inspection hatch.

We also carry a Mr. Funnel for transferring back our polished fuel, or potentially filling up from a bad fuel source. In the US this is quite unlikely, and as long as you use your fuel once a year, even with bad habits fuel quality will most likely not be an issue.

Acid Flush vs Engine Flush

Our engine uses raw salt water as coolant, which inevitably adds many salt deposits inside the engine. We’ve seen two recommendations on how to clean this — acid flush and an engine flush. An engine flush is normally done with fresh water (a rare resource), and mixed with some sort of soap to remove deposits. The raw water intake is hooked up to a 5 gallon bucket with the soap mixed in, and then the engine is run until the 5 gallon bucket is drained. Many boaters do this every time they go out.

An acid flush is the same idea, but a closed loop. A 5 gallon bucket is filled with a mild acid (in our case citric acid as it’s what we use for other cleaning), and that is run through the system and back to the bucket. On our engine, the water intake is the same location, but just before the exhaust elbow, we route the water back to the 5 gallon bucket. The thermostat is also removed so that the water goes through the engine itself, instead of recirculating to the elbow. All anodes are also removed (we put them in backward so water won’t escape). In order to push the acid and water through, we use a simple Submersible Fountain Pump. After flushing the acid, we pump through baking powder and water in order to raise the PH inside the engine. We then test with PH strips.

Of the two methods, we prefer the acid flush. An engine flush will never go through the entire engine due to the thermostat, and much worse, the soaps disperse suds into the marina or bay. The acid flush means extra work disposing of the water and more time running through (about an hour), but it removes many deposits. Our engine runs noticeably better after an acid flush. Ideally we’d do an engine flush with fresh water each time we go out, and an acid flush occasionally. However most inboard engines don’t seem to be cared for that much, and we’ve decided it’s too much work for us.

Engine Hardware and Mistakes

When working on the engine itself, we’ve had many mishaps that only get easier with experience. Some of the simple mistakes we’ve made are not plugging a cable back in the alternator and debugging the electrical system for hours, breaking bolts in the engine block, and not checking the thermostat enough. Most of the time mistakes are manageable, but they always seem to happen right in the midst of a important departure. We will no doubt keep making more, and have added some of the anecdotes of what has and hasn’t worked in this section. Always remember to take a picture while disassembling and possibly assembling. You can never have too many pictures.

One of our longest mistakes was not checking the engine thermostat for way too long. When we finally did check it, it was the night before a large trip, and we found that it had been stuck half open and half closed. It had probably been this way for years. This meant that the engine always ran a little too cold and then a little too hot. This no doubt contributed to our soot problem, though fixing the issue unfortunately didn’t solve it. After overnighting a thermostat from Orange County (couldn’t find any others in the state), we could finally make our trip one day delayed. We now keep a few extra on board and check in a pot of boiling water before large trips.

In another instance, we let a anode cover “weep” seawater for a little while, before the cover eventually stopped weeping after a couple hours. This seemed to be fine, but later when removing the anode and anode cover, a bolt from the cover snapped inside the engine block. The anode and anode cover were also welded together in a way where we had to dremmel off the anode, and then retap the cover itself. Initially we were quite nervous about removing the bolt, but following instructions from here, the bolt came out immediately with a “left handed” drill bit. This all seemed to stem from an ever so slightly uneven anode cover, and initially we used gasket sealant from an auto store to fix the leak. After we had more time we simply flipped the anode cover around and used the backside which seems to work. We still keep gasket sealant on board for emergencies, though it is quite overkill and hard to remove for most situations.

Other smaller annoyances have been around using the wrong tool for the job or not wanting to disassemble the engine. In order to access many covers (anode and impeller notably), it’s possible to install with disassembly. However taking off the starter motor for instance, means more consistent torque and in general a better result. Similarly, we used to try and remove oil and racor filters with strap wrenches. This was very difficult, and we’ve since bought different sized metal oil wrenches for all filters.

Tachometers and Engine Monitoring

In a similar vein to using the right tool for the job, the 1GM10 doesn’t come with a tachometer. We first tried to go without one, then we tried to use the kind with laser and reflective stickers. Both of these solutions mean that finding the RPM is very difficult, and RPM and heat are key pieces of monitoring information. Simply having alarms for when things go wrong has not cut it for us. Currently we use a Tiny Tach which is attached to the fuel lines and monitors RPM through the amount of fuel passing through. This works ok, but it tends to “race” between different RPM’s, and sometimes will not find the RPM at all. Still, it’s far better then guessing or moving the lader to monitor the engine as before.

For heat and engine temperature, we currently just use a heat gun and point it at the exhaust elbow and near the thermostat. This isn’t ideal, but we’ve felt what it’s like when the engine is running too hot, and the heat gun plus that understanding has been enough. When we first got the boat, we ran the engine 40 hours (with we think a broken thermostat as described above), and the entire cabin became very hot after many hours. The engine continued to run on that trip, but we’ve since never experienced anything like that and realize that was much too hot. While not ideal, it has given us confidence in the heat gun and common sense as a monitoring technique.