Engine Question

[Steve]

Last fall I bought a 1992 H28 with a 2GM20F engine. A couple of friends and I took a trip from Newburyport, MA to Boothbay, ME last weekend. For 10 hours we were fighting a 25 kt wind and 5 foot waves dead on the bow. I was working the engine pretty hard and noticed that I could only get 3250 RPM at full throttle. There was not any smoke or vibration -- in fact the engine seemed happy at this RPM. However, I thought I should have been able to get 3700+ RPM. What should I be able to get out of a 2GM20F?

 

[Roy Mosteller]

2GM20F RPM

I have never gotten more than 3250 RPM on my 2GM20F (30T - 1991). My Yanmar mechanic says although I might expect a little more the RPM is limited by my 3-blade prop. I always motor at 2750 giving me about 6.3 on knotmeter.

 

[nick8481]

Tach Varition

My tach reads 3400 at wide open full trottle no smoke,I have heard that the tach is not always accurate and will not always read the same on all boats.What I do is push trottle forward all the way until I see no inprovement in rpm 's and speed and no smoke,that will give me my top hull speed depending on conditions. nick

 

[Bill O'Donovan]

You done good at 3250

Yanmars typically do well at 85% of rated top RPM, I'm told by my mechanic. More importantly, you found the sweet spot and stayed with it. The spot varies on different boats and engines. Sorry you couldn't sail the trip, but at least you aired out the engine, always a good move.

 

[Ron D]

Sweet spot 3000 rpm

I have a 1991 H28 same engine. If I remember correctly "its been awhile" but the owners manual states run the engine at 3200 rpm for a max of 30 minutes and at 3000 rpm there is no limit?