Yanmar 3GMF on a Pearson 34

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osky

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Dec 16, 2010
2
Pearson 34 Annapolis
MY 1983 Yanmar 3GMF seems to work fairly well, 850 RPMs at idle, 3500 at full throttle forward)...but my pearson 34 only reaches 6 knots at max speed, and 5.5 at 2500 rpm (on flat water, no wind). Except for minimal, tiny amounts of whitish smoke coming eventually from the exaust, everything seems to be OK. Oil level OK, cooling OK, water through exaust OK, all filters and oils changed...why am I not able to reach the 7 knots that others do with this engine on a 34??? I know my boat has a 2 blade feathered prop. Could that be the reason? But the rpms seems to be OK. One more thing: Bottom is clean...
Any input will be appreciate it.
OC
 
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Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
It's all about the prop.

You govenor is probably limiting your max RPM's. I am guessing that you are under propped. Speak with a good prop shop and let them know what sized prop you have and find out what they recommend. (so far that is free)
 
seadaddler

seadaddler

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Dec 19, 2006
5,832
Hunter 36 Punta Gorda
History

Yes what has been your max speed since owning your boat,I would check the prop since you are getting max rpm and everything is clean it must be prop so talk to a few prop experts.
When my H-36 new could barely get 6.5 with hard work and changed to FLEX O FOLD with their advise to different pitch and now she will do 7 plus,I did compare with other 356/36 owners also what they had.
Nick
 
Ross

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
Re: History

I run a 10 horse with a 3:1 reduction gear and a 13 x 13 three blade . I am told that I could run a 15 X 10 three blade without overloading the engine. It is your prop.
 
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CHARLIE STAGE

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Jul 4, 2011
68
Cal 33 ft. MKII Clayton, N.Y. St. Lawrence Rvr
Yup prop! I have the Yanmar 3GM 30F engine in my 89' CAL-33 and it routinely goes beyond 7 knots when required without much stress.
 
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osky

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Dec 16, 2010
2
Pearson 34 Annapolis
Thanks to all for the replies! I've sailed her up to 7-8 knots, and I've heard of others who can get 7.5 Knts with same engine on other 34's. I'll ask the prop shop, but if this is the case (and not an engine problem) I might save my $$ for new sails instead..:)
Thanks again
O
 
S

Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
For just a few bucks you can get your existing prop re-pitched and still have money for sails too!
 
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