I have a 1GM10 Yanmar. Last season I could get 2500 RPM out of it, this year only 2200 and there is dirty grey/black smoke from the exhaust at full throttle. Last year there was no smoke. I have replaced all the filters but this did not help. Any suggestions? Thank you mckenzie
When was the last time that you checked the prop for growth?
– Geoff
Thanks for the reply Geoff, there has never been a problem with growth so I believe it must be something else. I don’t think it’s a compression problem because even if I use the decompression lever I have a hard time to hand crank it over on full compression. Today I took the mixing elbow off (I presume that’s the one coming off the block ?) and it was as clean as a whistle. I blew through the exhaust pipe by mouth and that seemed to be clear, I could hear the water bubbling in the wet muffler and of course there was some resistance there. My next plan is to take the injector out and make sure that it’s atomizing and not dribbling.
Hi,
Have you checked the engine air intake/coarse filter? I had a similar problem a couple of years ago when the foam backing of the soundproofing material slowly got into the air intake of the engine. Mixture is then too rich and does not burn properly, generating black smoke.
Good luck
Thanks for the reply Geoff, there has never been a problem with growth so I believe it must be something else.
Before I spent too much time taking apart parts of the engine, I would want to make sure that there wasn’t some fouling. Perhaps you’ve got a bag, or something, wrapped around the prop. I’ve seen it happen.
– Geoff
important test is whether you are still rpm constrained out of gear, if not I will give odds on the prop.
Hi guys,
I am new to this web site (Sunday 27th Sept. 2009) and not really sure what I’m doing in terms of how to respond to your individual answers. Please bear with me, given time I’ll probably figure it all out! Ereiss, when she’s out of gear I can push the “throttle” to full and get 3000 rpm + (briefly, for safety) , same as last season. When I back out of my slip I can go full astern at 2800 rpm or so (I didn’t check the exact rpm, same as last year though). However, last year I was getting maybe 2500 rpm or more at full ahead with a nice clean exhaust and doing 5.8 knots or whatever, now I have max 2200 rpm and 4.6 knots. So here’s the mystery :- now when I put my “throttle” to about three quarter speed I have 2200 rpm,with clean exhaust and when I open it up to full I still have 2200 and now I have this dirty grey / black smoke, not a lot but it’s there. The prop is an “Eliptec” two blade folding, similar to the “Martec”. Today I took off the angled pipe (is this the “mixer” pipe) from the block and it was very clean, I blew through the exhaust pipe by mouth and it seemed to be ok. If there was a bag or something around my prop would I not get some vibration?
Just as a matter of interest I am sailing out of Picton, Prince Edward County, Ontario, Canada on Freedom 25 #215 (Prince Edward Yacht Club).
Thankyou for your help guys, it is much appreciated.
george MCKENZIE hunt.
The 10GM is notorious for getting a garfed up exhaust valve. It creates the symptoms you describe. I’d certainly check for constraint on the air intake as advised above before I did anything.
A quick note for anyone owning one of these engines. Your last thing to do when winterizing is to roll the engine up onto to compression by hand and leave it there. This ensures both valves closed and the cylinder closed to outside air.
George
OK, thankyou George.
Mckenzie, I have had exactly the same symptoms on all my boats, getting worse as the season prgresses and the anti fouling comes due for replacement. I put the boat on the slipway, waterblast and re-antifoul and voila! problem gone until the growth builds up again. Other suggestions put forward are also valid, air intake restriction, faulty injector etc would give you the black smoke as well, but the symptoms your engine exhibits are closer to those of an engine in overload condition, just finding the drag (from a fouled hull) too hard to overcome. Cheers