How I learned to stop worrying and love the Yanmar 1GM10

Although we had some interesting sailing adventures this season, as a whole this has been the quietest sailing summer so far.  This is primarily because of this guy.  The 200 pound rusted and gristled heart of Hurry On, the Yanmar 1GM10.  When we bought Hurry On, it had been a few years since this beast ran, with the previous owner saying we could expect some black smoke.  My wintertime reading explained this was one of the symptoms of unburnt fuel, much fun to look forward to.

Checking/Changing the Oil

Job one was checking and changing the oil.  Because it was so long since the engine last ran, I tried to make sure it was lubed up before starting.  This was simply a matter of pulling out the kill switch and turning it over  for a few seconds.  In order to warm up the oil, the next step was to run the engine for a few minutes.  Being the first time in a few years, really had no idea what to expect.  Away she went, loud and banging, it sounded terrible*!  Surely this thing was going to break free of its engine mounts!  We killed the engine.  (*editor’s note –  I later discovered that the sound of this engine was completely normal.  Because it is a one cylinder, there is nothing to balance out single the piston, hence the bang! bang! bang!  Once the rmps increase, the engine actually gets considerably quieter)

There was a neat little oil extraction pump in one of the lockers, which I never used before.  You put the hose in the dipstick hole till it hits the bottom, pump about 40 times and wait about 10 minutes until you hear it gurgling up the last few drops.  For some reason, the oil filter on the Yanmar 1GM10 screws on horizontally.  This is a pain in the arse, and can get a bit messy.  You can get Yanmar filters around here for about 10 bucks, or Fram PH6607 for $7.

Changing the Fuel Filter

Remember to turn off the fuel at the tank!  If you can manage to get the filter case off, its a pretty simple replacement.  Just have to remember to bleed the engine at the three bleed points when you’re done.

Changing the Impeller

The bit that sucks the raw salt water up through the engine is the impeller.  It sits behind the alternator belt.  When I removed the speed seal, the impeller seemed to be intact with no cracks or anything.  I replaced it with the new one anyway, and kept the old one as a spare.  A little bit of dish soap for lube and then back on.  I noticed that no matter how tight the seal, there seemed to be a single drop of water that leaked out once every 10 seconds.  The leak doesn’t appear to be coming from the seal though, rather from the pump housing itself.


Yanmar 1GM10 water pump speed seal


Behind the seal


Bit of dish soap to keep things lubed

Sacrificial Zinc

I should mention that for most of these engine projects, that they are made infinitely more difficult by the lack of space and accessibility.  With the exception of changing the oil, all of these jobs can only be done with only one hand, and, unless you can strategically duct tape a compact mirror and flashlight in place, you are likely navigating by feel. The zinc is inconveniently located on the port side of the engine.  And it is another one-handed, no-looking kind of thing.

In an effort to get a look at what was going on back there, I snapped a pic after I got the old plate off, this is the best I could muster.

In an effort to get a look at what was going on back there, I snapped a pic after I got the old plate off, this is the best I could muster.

Not sure how long that guy was in there but there ain't much left of it! It looked like a high temperature calking was used. I put a regular gasket in this time.

Not sure how long that guy was in there but there ain’t much left of it! It looked like a high temperature calking was used. I put a regular gasket in this time.

Alternator Belt

This was by far the quickest and easiest fix.  After a particularly squealy, noisy start, the the original belt appeared to lose quite a bit of tension.  The replacement was put on by loosening the alternator, removing old belt, putting the new one on, then snugging up the alternator with a hammer handle, and tightening back up.

Exhaust Elbow

These have a finite life.  Their job is to combine the raw water with the exhaust and safely put it out the back of the boat.  What happens over time, and what happened in our case, the inner sleeve perforated.  So when the water made it to the elbow, it went out the exhaust, AND into the cylinder head as well.  A new elbow was 220 Canadian flippin’ dollars.

Current Condition

The engine starts easily and runs.  At the moment, it appears to be going through a lot of oil with no visible leaks.  Also, there is a great deal of white smoke when in neutral at about 2500 RPMs, under load it will only get up to about 1500 RPMS.  Ok for short trips into the harbour, but for any longer distance this will have to be rectified.  May be time to think about a rebuild, or at least call in a pro!



Filed under Projects, Videos

3 responses to “How I learned to stop worrying and love the Yanmar 1GM10

  1. Alan

    Had same mixing elbow issue as well as it lead to Exhaust Valve pitting and lack of power.
    Took off head and purchased both valves..
    After that fix, started easily and ran perfect.

    Good little engine
    Do you have a working fuel gauge? I suspect the sending unit on mine is faulty.

    • RC

      Funny you mention the fuel gauge. Nope, doesn’t work! When the key turns on the gauge goes straight to empty, so I think it may be a problem with the sending unit.

      • Alan

        Must be as i took a potentiometer (Variable resisitor) and hooked it up instead of sending unit,, as i turned the pot, the gauge needle moved….
        I unfortunately filled up the fuel tank and could not take the sending unit out in the spring as the fuel in the filler pipe would have overflowed out of the sending unit hole.
        Maybe this winter/spring i will replace..

        Enjoy you boat.. its a great boat to sail.. If you are in Halifax and have time, come for a sail on mine if you wish


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