Low RMP in Yanmar motor

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Charlotte14150

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Jun 2, 2004
4
- - Clinton Lake, IL
I have a 2005 3YM20 Yanmar motor in my 2006 Catalina 309 sailboat. It has only 330 hours in it. Recently, it cannot go higher than 2500 RPM. I have changed oils, filters according to the user’s manual. A local Yanmar technician also adjusted the valves the last fall. I don’t know if it is related, but since tehn, only occasionally, I have experienced the lower RMP problem. When I called him he said it must have been the barnacles on the bottom of the boat. Today morning, as usual, a diver cleaned the bottom and the prop. Still, the RMP, in the dock, does not go higher than 2500. I also checked the transmission and throttle cables, they are fine in length. When I disengage the transmission from the motor, the RMP can go all the way to 3600. Has anybody experienced similar problem?

Tibor Gyires

Catalina 309, “30”, Charlotte
St. Pete Beach
 
T

tahomathundr

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Jun 4, 2009
92
Catalina 309 Swantown Marina Olympia, WA
Tibor, I have not had a problem, but it sounds like the trans is putting a big load on the engine. If the engine runs up to 3600 rpm in neutral that sounds OK. How is the oil in the trans? I would be looking at that trans as a possibility. Bob C309 #20
 
C

Charlotte14150

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Jun 2, 2004
4
- - Clinton Lake, IL
Bob,

Thank you for the tips. I checked the trans oil, filters, etc. They were fine. Eventually, it turned out that the u-shape elbow mixing the exhasust gas with water was clogged with exhaust residue. After replacing two sections out of three, the motor now runs 3500 that is almost 3600.

Thank you again for your reply.

Tibor
Catalina 309, “30”, Charlotte
St. Pete Beach
 
BoxedUp

BoxedUp

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Feb 9, 2010
30
Undecided 30' Something Oyster Bay, NY
Tibor,

Have you found out what caused the elbow to clog? Do you run the engine at low RPM's for extended periods of time?
 
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