Hello all. I have an INTERMITTANT rpm decay on my little Yanmar. It has happened seveal times over the last few years, and again just recently. I've had this boat for quite a while, and the engine has been meticulously maintained. The mixing elbow was clogged (the raw water port) a few years ago, yielding some overheating problems, and was replaced. The fuel filters have been replaced regularly, and again recently when this problem recurred. So, here are the symptoms: Every once in a while (and, of course, this always happens when it would be really nice to have full power) the engine cuts back from cruising rpm (I run at around 3200 when the wind dies and I need to get somewhere) to about 2300 rpm, with no black smoke or anything else unusual to note, and, even with the throttle pushed wide open, it will just stay at or near that rpm indefinitely, but then it eventually gets back to normal operation after a a while (a few minutes, maybe a few hours, or sometimes not until the next time I go out), at which point it will achieve full power at 3500 rpm or so, and behave normally for days, weeks, or even months. I've tried the obvious stuff (filters, filling up, Startron, etc) to no avail. The throttle linkage is working normally. I've heard the govenor is tricky to mess around with, but I might give it a try... but, honestly, the intermittant nature of this problem has me stymied. Any Ideas? Thanks- Rick
Another 2GM20F RPM issue:
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Intermittent problems are the hardest to diagnose over the net. Ask yourself, what do all these occurrences have in common? Weather, water temp, on one tack or the other, other heavy loads turned on, choppy seas, negotiating a sea of kelp or crab pots? My first impression is either there is an additional load or the engine is getting too little fuel. Since you stay on top of the fuel filters that leaves a pump (lift or injector), a fuel tank restriction (pickup or vent) or throttle linkage. I can't imagine the throttle linkage would let the engine come back up to full power once it slipped so I'm thinking fuel system pump or clogged plumbing. It could be a gremlin!! You might want to raft up with someone and entice the gremlin to your, soon to be ex-friend's, boat.
Intermittent problems are the hardest to diagnose over the net. Ask yourself, what do all these occurrences have in common? Weather, water temp, on one tack or the other, other heavy loads turned on, choppy seas, negotiating a sea of kelp or crab pots? My first impression is either there is an additional load or the engine is getting too little fuel. Since you stay on top of the fuel filters that leaves a pump (lift or injector), a fuel tank restriction (pickup or vent) or throttle linkage. I can't imagine the throttle linkage would let the engine come back up to full power once it slipped so I'm thinking fuel system pump or clogged plumbing. It could be a gremlin!! You might want to raft up with someone and entice the gremlin to your, soon to be ex-friend's, boat.
I had the same problem
last year in the keys. I even took the mixing elbow off and cleaned it out at anchor. Finally figured it out after several days. Seaweed wrapped around the prop. Now, when it slows down, I just pop it in reverse for a few seconds to clear the prop and all is well. Hope it helps. John
last year in the keys. I even took the mixing elbow off and cleaned it out at anchor. Finally figured it out after several days. Seaweed wrapped around the prop. Now, when it slows down, I just pop it in reverse for a few seconds to clear the prop and all is well. Hope it helps. John
Bill Roosa Said
Make a point of checking things out,sounds like some thing with the engine fuel system,in that too long period when it is happening. I would check your fuel system one thing at a time,maybe the pump or govenor is needing cleaning or rebuilding,fuel hoses,fuel tank is needing checking. How old is the engine and how many hours. Nick
Make a point of checking things out,sounds like some thing with the engine fuel system,in that too long period when it is happening. I would check your fuel system one thing at a time,maybe the pump or govenor is needing cleaning or rebuilding,fuel hoses,fuel tank is needing checking. How old is the engine and how many hours. Nick
DIEING THROTTLE
It sounds like a fuel supply promblem. I have heard of the teflon tape used for sealing pipe joints getting sucked into small openings and restricting fuel flow. It is hard to detect becauseit only happens intermittingly. Undue all your connections one at a time and look for the tape overlapping the end of a pipe or tube opening.
It sounds like a fuel supply promblem. I have heard of the teflon tape used for sealing pipe joints getting sucked into small openings and restricting fuel flow. It is hard to detect becauseit only happens intermittingly. Undue all your connections one at a time and look for the tape overlapping the end of a pipe or tube opening.
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