Boat was launched yesterday and all went well except that I noticed that it ran very rough even for a 3 cylinder diesel at idle speed. A lot of vibration and shaking. I had to wait 40 minutes for a draw bridge to open, and I spent some time in neutral. As soon as I advanced the throttle it smoothed out. I did not want to shift at higher RPM's so I backed it down to place it into gear, and as soon as I did I thought I was going to stall it was so rough. It never actually stalled. I did replace the Racor and engine mounted filters, and she seems to start fine. Could there still be some air in the fuel lines?
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idle speed
My guess is to reset the idle speed, bet it is too slow. You did not say what engine except it was a 3 cylinder. If it is the yanamr 3 gm idle speed is around 850 rpm. When a diesel is to slow it will shake very very badly. Simple fix on yanmar engine, it is a screw adjustment on the fuel pump linkage. If it was getting air in the fuel it most likely would not have stayed running as long as you said,especialy since the engine ran well at a faster then idle speed,most times if air get into the system from a filter change it is "run" thru in a matter on minutes or the engine will die out. Check out the web site below for good info on yanmar's if that is what engine you have. Take note on the part about yanmar tachometers reading fast so don't be afraid to have your tach read high if the trans is going in and out of gear smoothly.
My guess is to reset the idle speed, bet it is too slow. You did not say what engine except it was a 3 cylinder. If it is the yanamr 3 gm idle speed is around 850 rpm. When a diesel is to slow it will shake very very badly. Simple fix on yanmar engine, it is a screw adjustment on the fuel pump linkage. If it was getting air in the fuel it most likely would not have stayed running as long as you said,especialy since the engine ran well at a faster then idle speed,most times if air get into the system from a filter change it is "run" thru in a matter on minutes or the engine will die out. Check out the web site below for good info on yanmar's if that is what engine you have. Take note on the part about yanmar tachometers reading fast so don't be afraid to have your tach read high if the trans is going in and out of gear smoothly.
My recollection, Chief, is that you have an M25
in your C30. We have one in our C34. Same issue. Over the course of time, the idle adjustment, which is simply the "throw" on the lever at the engine end of the throttle cable gets out of whack. Two choices: don't back all the way down on your throttle and keep a minimum of 1000 to 1100 rpm in a sweet spot, or adjust the linkage at the engine end. We chose #1, but have to caution new helmsmen to not back all the way off. Next step - fix it. We'll get there. You can engage the shift from 800 to 1500 rpm without damaging the Hurth transmission, indeed it's almost better to have some higher revs when shifting gears. You do NOT have an engine problem. If you had any air in the lines it would not work AT ALL.
in your C30. We have one in our C34. Same issue. Over the course of time, the idle adjustment, which is simply the "throw" on the lever at the engine end of the throttle cable gets out of whack. Two choices: don't back all the way down on your throttle and keep a minimum of 1000 to 1100 rpm in a sweet spot, or adjust the linkage at the engine end. We chose #1, but have to caution new helmsmen to not back all the way off. Next step - fix it. We'll get there. You can engage the shift from 800 to 1500 rpm without damaging the Hurth transmission, indeed it's almost better to have some higher revs when shifting gears. You do NOT have an engine problem. If you had any air in the lines it would not work AT ALL.
Idle
Thanks to all who replied. It is indeed a Universal M25XP with just under 1,000 hours. I will try to adjust the linkage, as sometimes the wife is at the helm. I would rather have it fixed, then to try and keep a constant eye on the tach.
Thanks to all who replied. It is indeed a Universal M25XP with just under 1,000 hours. I will try to adjust the linkage, as sometimes the wife is at the helm. I would rather have it fixed, then to try and keep a constant eye on the tach.
Good idea, but the tach is not really all
that far away, plus, it doesn't hurt to get used to finding the right spot. I can do it with my eyes closed by now. Your boat, your choice. Anyway, suggestions on how to do it (in addition to getting the parts blowup from marinedieseldirect): Have your wife at the helm, could be with engine off, watch how the throttle cable works the throttle cam on the engine from stop to full, figure out how to adjust nuts by how the thing moves. That's what I'll do, eventually. Good luck, fair winds.
that far away, plus, it doesn't hurt to get used to finding the right spot. I can do it with my eyes closed by now. Your boat, your choice. Anyway, suggestions on how to do it (in addition to getting the parts blowup from marinedieseldirect): Have your wife at the helm, could be with engine off, watch how the throttle cable works the throttle cam on the engine from stop to full, figure out how to adjust nuts by how the thing moves. That's what I'll do, eventually. Good luck, fair winds.
Also
Whilst I agree the most likely cause is idle low speed, it must be remembered that the engine mounts play a big part too. If one or more mounts are broken or the hold down nuts are loose the engine is free to jump about as it pleases. Only one loose mount could cause the above effect.
Whilst I agree the most likely cause is idle low speed, it must be remembered that the engine mounts play a big part too. If one or more mounts are broken or the hold down nuts are loose the engine is free to jump about as it pleases. Only one loose mount could cause the above effect.
For What It's Worth - My Vibration After Launch
Not to suggest that you don't take into account the previous suggestions. When I purchased my 1980 boat last summer and launched in October, it had been on the hard for a couple of years. I have a 2 cylinder Yanmar. The vibration at all rpms, with the exception of a few smoother "rpm nodes", was significant. Took a couple/three months but the vibrations are now diminished quite a lot and I no longer need to hunt for the lowest vibration rpm around the motoring speed I want. Guess this is why its recommended that engine/shaft alignments shouldn't be made until after the boat has been back in the water for a period. I've read and have been told that the hull changes shape after being on the hard and it takes time for it to conform back to normal back in the water. Idle for my engine is at the specified 650 rpm (per the Yanmar tach). And yes the engine shakes the whole boat at that rpm. (But not as bad now as when I first launched) As the others have posted, I also tend to tweak the throttle say at warm-up to about 800-900 rpm and things settle down much better. Thanks for the post and responses. I'm prompted now to look if the idle on my engine can be adjusted up a bit.
Not to suggest that you don't take into account the previous suggestions. When I purchased my 1980 boat last summer and launched in October, it had been on the hard for a couple of years. I have a 2 cylinder Yanmar. The vibration at all rpms, with the exception of a few smoother "rpm nodes", was significant. Took a couple/three months but the vibrations are now diminished quite a lot and I no longer need to hunt for the lowest vibration rpm around the motoring speed I want. Guess this is why its recommended that engine/shaft alignments shouldn't be made until after the boat has been back in the water for a period. I've read and have been told that the hull changes shape after being on the hard and it takes time for it to conform back to normal back in the water. Idle for my engine is at the specified 650 rpm (per the Yanmar tach). And yes the engine shakes the whole boat at that rpm. (But not as bad now as when I first launched) As the others have posted, I also tend to tweak the throttle say at warm-up to about 800-900 rpm and things settle down much better. Thanks for the post and responses. I'm prompted now to look if the idle on my engine can be adjusted up a bit.
Engine mounts
Sounds like engine mounts have gone south. Fuel problems will happen at all speeds in a diesel. have someone operate the throttle while you observe the engine mounts. It is very common to see the engine jump when you put it in gear and the prop applies torque to it.
Sounds like engine mounts have gone south. Fuel problems will happen at all speeds in a diesel. have someone operate the throttle while you observe the engine mounts. It is very common to see the engine jump when you put it in gear and the prop applies torque to it.
sounds like some air, maybe a loose fitting on the filter or bleeder.
It would run great at throttle up but have problems at idle. r.w.landau
It would run great at throttle up but have problems at idle. r.w.landau
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