Is it normal to lose RPM'S over time. I have an 89 Cat 30 with a Universal M25XP with around 900 hours. I never go over 165 degrees, and I can easily hit 3200 RPM'S at the dock (not in gear). I noticed while motoring over from my winter yard that under power and in gear I was maxed out at around 2600 RPM'S. I will swear that last year I maxed out closer to 3000. The bottom is as clean as it can be (new paint). The prop has not been changed and is the standard 2 blade fixed. Is the engine losing compression? Is there a problem with the transmission?
Engine RPM'S
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Not the problem
Thanks for the reply Stu, but after the first season with the boat I adjusted the throttle tension, and that has not been an issue since. The throttle stays exactly where I want it. Vibration is not the issue, I definitely lose RPM's which may be perfectly normal. I know I have never been able to get the same readings in gear as I do in neutral. I can understand this, as the load of the transmission, shaft and prop add load to the engine. The issue I worry about is the additional loss over time. Is this something I should have checked by a mechanic (as if I could find a good one where I live) or just live with it. Is this normal with diesel as they age?
Thanks for the reply Stu, but after the first season with the boat I adjusted the throttle tension, and that has not been an issue since. The throttle stays exactly where I want it. Vibration is not the issue, I definitely lose RPM's which may be perfectly normal. I know I have never been able to get the same readings in gear as I do in neutral. I can understand this, as the load of the transmission, shaft and prop add load to the engine. The issue I worry about is the additional loss over time. Is this something I should have checked by a mechanic (as if I could find a good one where I live) or just live with it. Is this normal with diesel as they age?
Take a Pick
A number of things can cause something like that. I strobed my tac to find out it was off 100-300 rpms depending on the speed of the engine. At lack of fuel flow wouldn't necessarily show up without a load but would once loaded up. The same would hold true for a constriction in the exhaust side. The injectors could have an influence, but I would go there last.
A number of things can cause something like that. I strobed my tac to find out it was off 100-300 rpms depending on the speed of the engine. At lack of fuel flow wouldn't necessarily show up without a load but would once loaded up. The same would hold true for a constriction in the exhaust side. The injectors could have an influence, but I would go there last.
Thanks for the suggestions
The fuel filters are new this season, Racor as well as engine mounted. Also, I replaced most of the exhaust system (new Westerbeke riser, muffler). I have not had injectors checked, maybe I should have them serviced or replaced.
The fuel filters are new this season, Racor as well as engine mounted. Also, I replaced most of the exhaust system (new Westerbeke riser, muffler). I have not had injectors checked, maybe I should have them serviced or replaced.
unlikely to be injectors
Don't know much about diesel engines, but I do know that injectors are supposed to last at least 2000 hrs without servicing. My C30 of the same vintage and with a bit over 800 hrs happily does 3200 rpm in gear (although I rarely do that, cruising generally at around 2400/2600), so you definitely seem to have a problem. Having tinkered with motor cars (but not diesels)in my youth, I would suspect a compression or airfilter issue if your loss of rpms only happens in gear, but I don't know if that makes sense with a diesel. Good luck - or get a mechanic....
Don't know much about diesel engines, but I do know that injectors are supposed to last at least 2000 hrs without servicing. My C30 of the same vintage and with a bit over 800 hrs happily does 3200 rpm in gear (although I rarely do that, cruising generally at around 2400/2600), so you definitely seem to have a problem. Having tinkered with motor cars (but not diesels)in my youth, I would suspect a compression or airfilter issue if your loss of rpms only happens in gear, but I don't know if that makes sense with a diesel. Good luck - or get a mechanic....
could it be...
something around your prop? That sounds exactly like my situation - except I had stuff growing on my prop and a line wrapped around it. There was no vibration, just low rpm in gear. A friend dove in and pulled it off.
something around your prop? That sounds exactly like my situation - except I had stuff growing on my prop and a line wrapped around it. There was no vibration, just low rpm in gear. A friend dove in and pulled it off.
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