1GM10 questions

[rperret]

Have a 2004 1GM10 0 after a minor glitch, the engine starts and runs great.

What I do notice is that the motor tends to shake somewhat whilst at idle (approx 900 rpm on the control panel). Now I know that the 1GM's tend to be sewing machine like due to the single throat - so maybe it's normal. It tends to move about 1/8-1/4" side by side at low idle - then starts to smooth out as it gets to 1500+ RPM. Assume this is BAU for the 1GM10.

Note that the motor was previously idling at about 600 RPM, and the yanmar spec seems to indicate a 875-900 rpm at idle. Since I raised the idle another item has arisen - when I shift into forward - i hear the clunk as it goes into gear - i did not hear this before. Any idea what might be causing this? Maybe the higher RPM? I have a Kanzaki (sp?) 2.61 ratio gear box.

Any thoughts appreciated.

Rick

[Rickm505]

Drop your idle back, as the thunking can not be good. I have a pair of these engines in my catamaran and they do shake a bit. If you notice it shakes a lot, invariably it's a fuel system or fuel problem. Usually water in the fuel.

Any smoke coming from the exhaust?

Rick in Florida

[Gary M]

Good advice Rick, I would set the idle as low as it will run. The thud when you shift at a higher RPM has to be hard on your transmission. My last boat had a 1GM and current a 2GM they do rock around a bit, no big deal.

The plywood support structure on mine is not as ridgid as they should be, actually it is delaminating, so mine shakes a bit more than it should. I hope to strengthen or replace them this winter.

Gary

[Goodnewsboy]

Setting a diesel to a low idle speed may not be such a good idea. Yanmar prescribed the idle setting for a reason.

Make sure the transmission is filled to proper level with the right oil and if it still clunks, it may need an adjustment. Look at your Yanmar service manual.

[rperret]

A thought - i neglected to mention that I have a Martec folding prop. Now, when I do hear the slight clunk - i don't feel the boat surge forward at all. Could it be the sound of the prop opening up and engaging?

[sailingdog]

Yup... the prop could make the clunk. Might be worth checking to see where the clunk is coming from. If it is from the prop... then it is probably good. If it is from the transmission...then it is probably bad.

[Goodnewsboy]

The poor little 4 cycle engine has only one power stroke per 2 revs. Give it a break. It is going to shake more than its multiple cylinder cousins, (hence the higher idle speed) and I can see where the torque spike caused by an unfolding prop could be quite harmful, perhaps to the extent of wiping a bearing, bending the connecting rod, or breaking the crank.

[rperret]

Originally Posted by RickBowman

A 1GM10 shakes at an idle. I was told not to use a folding prop on a 1GM10, as it would invalidate the warranty of the engine. This info came from the dealer that sold the new boat in 1999.

Called MackBoring technical support -they told me that a folding prop was not a problem. I just put in some fresh fuel today and i noticed it didn't complain much when I placed it in gear. Also went more slowly from idle so it seems to have helped. Who knows.