how hard can you run the 8hp yanmar?

[John]

I am new to small diesel ibs. Have owned tons of gas outboards my entire life. Can you run the 8hp yanmar at full throttle for a long period of time as long as the cooling system is working up to par? No tach with the boat I just bought.

 

[John K Kudera]

in a word, Yes!

I have a friend with one of those, he is Mr non maintenance, always ran at full throttle, with a three blade prop. He owns a very early model H27. Always starts, runs well!

 

[Terry]

Hi John, if it were my boat I would run the....

propulsion engine about three quarters throttle while cruising. I would estimate that puts your RPM at around 3,000, which should push your boat along at hull speed. You can run it harder but all you do is increase fuel consumption.We had an 18 horsepower 2GM and cruised it for hours on end at around 3,000 RPM. It pushed our H28 along at 6.5 knots. Increasing it to max RPM made less than a half knot difference, so left it at 3,000.Terry

 

[Bob Talley]

Run Wide Open

I had a H27 1979 for about 16 years. Always pushed the thottle to the max setting and backed off just slightly. The boat ran fine like this for hours on end. Never had a problem with the engine.

 

[Andy]

In the same boat

Like you, I had no experience with diesels before we bought an H27 (82) 2-1/2 years ago. Advice from various sources was much the same as you have received here. When in the clear, I try to keep it at 3000, it is hull speed. Pushing it harder does, as one person suggested, seem to waste fuel. Of course when you use about 10 gallons a year, so what? I would not be concerned to push harder if conditions made that necessary. Do realize, however, that this engine (depending on your boat) is not going to allow you a lot of options in boat handling so plan ahead and practice so you know the limitations.Andy"Baroque"

 

[robert]

yanmar 1 cylinder, running at peace

you can push this little engine hard, but why try to kill it. Listen to it. when it starts to scream, back off a little. You'll know what I mean . You want to have it run in a groove. Thats when the harmonics of the engine, transmission and the engine struts are at peace. when you have severe shaking or bucking, try to first increase throttle. If no luck try to decrease throttle. Your boat will tell you where it wants to run. By the way these are very NOISY engines by nature.

 

[Tim McCarty]

My former engine was a 1gm

on my old, much-loved '82 h27. If I recall, I used to run it at about 3200 rpm. I now have a '94 29.5 and run the 2gm at about 27-2800 rpm.