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Diesel This is a new forum dedicated to diesel engines and their applicable accessories.


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Old 05-20-2014
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Yanmar 1GM issues

I am the new owner of a 1984 Sirius 28 sailboat with a Yanmar 1gm and quickly learning the previous owner did very little regular maintenance on the engine. Despite the marine surveyor who stated the boat is in good shape, I have replaced the thermostat, zinc anode, primary and secondary fuel filters, oil filter, air filter, both engine and gearbox oil, seawater intake hoses, seacock, one rusty oil line and checked the exhaust elbow for blockages (none). The hull and prop have been cleaned and I am about to have the packing replaced in the stuffing box. Although this has been a terrific learning opportunity, the engine is still giving me some concerns. The engine starts easily and will reach a max of 3100 RPM in neutral, but only 2400 RPM when in gear which will get the boat up to 6kts. The exhaust is whitish in colour and there appears to be only a low amount of water being expelled from the exhaust, although I do not know what the normal amount should be. Additionally, when accelerating quickly there is a “clanking” noise in the engine compartment – there is no noise if the acceleration is gradual.
I’ve scoured the forums and internet to get some answers to no avail. I am able to perform some fairly basic repairs and would really appreciate any assistance you can provide to identifying potential reasons for the low RPM, whitish exhaust, low exhaust water outflow and “clanking” noise when accelerating quickly.
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Old 05-20-2014
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Re: Yanmar 1GM issues

rod bearings...the clanking happens cause you are loading up the engine...if gradual you arent pushing the engine much

whitish smoke can indicate among other things coolant into oil or viceversa...

there is a very similar thread here with a 2gm with similar issues except for the clanking...
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Old 05-20-2014
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Re: Yanmar 1GM issues

Could also be knocking caused by bad timing, if you don't have a shop manual for the engine, let me know and I can email you a link.
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Old 05-20-2014
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Re: Yanmar 1GM issues

I think your 1gm is raw water cooled. Are you sailing in salt water? You say you replaced the thermostat- this is good. How did the cooling water passages look in the engine when you replaced tha anodes and thermostat? If they looked clogged, you can do an acid flush of the engine. The low water may be due to blocked passages. Contact a yanmar dealer and talk to them about what chemicals to use for the flush. You can do it yourself, just need to use right chems or you could damage the engine (you might need to remove t-stat and anodes during flush). Make sure the raw water suction strainer and screen on the outside of hull are clean and not causing blockage.

My engine will knock if rpms are raised to fast- make adjustments slowly and change gears 900 rpm or below.

I flush my raw water cooled engine with fresh water after each use to slow corrosion.

You did not mention if you replaced the rubber raw water impeller- that could be your problem with low water flow.

Another thing- not sure if the boat sat for a long time- might be a good idea to drain the old fuel and start with fresh diesel- small engin like that buy the fuel from a non marine source- less chance of having water in the fuel. Bad fuel can cause combustion problems.

Last edited by casey1999; 05-20-2014 at 09:13 PM.
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Re: Yanmar 1GM issues

you shouldnt knock no matter what...changing the impeller will have no effect on that but it will help you water flow issue

it also will not do anything with the smoke you are experiencing

knocking in some extreme cases can be caused by carbon buildup too...



the other thread I mentioned will give you clues into the possibilities of what you might have going one with yours

a shop manual will go a long ways in helping you determine what course of action to take

good luck
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Re: Yanmar 1GM issues

I had a Yanmar 1GM in my Cape Dory 25D. It had about ten hours on it when I bought it and sounded like someone banging on an anvil with a hammer when it was running. Despite that, it was absolutely reliable and used so little diesel it was easy to forget to even put any in the tank.
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Re: Yanmar 1GM issues

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Originally Posted by Group9 View Post
I had a Yanmar 1GM in my Cape Dory 25D. It had about ten hours on it when I bought it and sounded like someone banging on an anvil with a hammer when it was running. Despite that, it was absolutely reliable and used so little diesel it was easy to forget to even put any in the tank.
I have heard the 1 cylinder yanmars run a lot rougher than the multi-cyclinder. One cyclinder does not have anything to counter balance.

OP- you may also want to check you engine mounts are good- lift up on the engine and see if the rubber has broken loose from the metal mount.
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Re: Yanmar 1GM issues

I'm not totally clear what your problem is. As a few others pointed out, the 1 cylindar deisel is a loud engine. When you accelerate rapidly the engine does get louder until it gets to the requested RPM's.

I'm not convinced the sound you're hearing is a problem.

On the other hand not getting above 2400 rpm's is a tangible problem. It may just be that the prop is too large. 6 knots for a 28 ft boat with this engine is pretty reasonable (that's my maximum).

Also note that there is a difference between the 1gm10 and the 1gm, with the 1gm10 being more common.
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Re: Yanmar 1GM issues

Wow, that is quite the response, thank you all. So to answer a few questions, yes the boat is in salt water and after I replaced thermostat and zinc anode which were in terrible shape I believe in hindsight that some "bits" may have clogged the cooling system. As suggested I'll have a chat with Yanmar folks to find out what to use to flush it, and how to do it as all of this is new to me. After reading some more about the white exhaust I have a theory. With a low flow of water out the exhaust the small amount of water entering the hot exhaust in the exhaust elbow is creating steam. So first step is to improve the flow of raw water cooling so see if this fixes the problem.

The "clanking" sound described in my OP sounds more mechanical and only occurs when in gear and accelerating quickly vice gradually to full throttle. One suggestion is that it could be rod bearings, but I hope not as this sounds like a complicated and expense repair.

As for the low RPM, the original prop is still with the boat, everything has been cleaned on the hull and prop. Possibly the injector needs some TLC and or timing. Again this is a bit out of my comfort level to attempt on my own so may have to seek professional assistance.
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Re: Yanmar 1GM issues

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Originally Posted by PaulinVictoria View Post
Could also be knocking caused by bad timing, if you don't have a shop manual for the engine, let me know and I can email you a link.
I would really appreciate the link to the shop manual. I am a newbie to this forum and unable to PM you as I do not have enough posts, but are you able to PM me with the link?
With thanks from your V.I. neighbour in Comox.
Mike
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