The 3JH3E is a 3800 RPM engine. Yanmar wants your prop to allow you to attain at least 3700 -3800 RPM at full advanced throttle..
Yanmar cruise RPM
- Thread starter Ken Cross
- Start date
The 3JH3E is a 3800 RPM engine. Yanmar wants your prop to allow you to attain at least 3700 -3800 RPM at full advanced throttle..
Interesting-I'll recheck that top speed next time I on the boat; the prop is a Volvo fixed two-blade, LH 16 x 13; aluminum.
Maine sail..... On another thread somebody mention that sometimes the tach could be off due to age. I replaced my alt a couple years ago, is it a good investment to buy a new tach?? Also assuming the tach is accurate, I guess a prop shop should be able to size and pitch a prop based on the engine / transmission / boat specs...... Out of curiosity, I am going to purchase a new prop next season and was wondering what you have on your boat..... Thanks!
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My tach only works half the time so I run my engine based on sound (easy to tell the rpm it likes) or speed. other than that I operate my engine the way the manual says, meaning if I run it a long time at low load I just run it up high every once in a while.
My 2GM20F maxes out at 3,800 rpm out of gear and 3,600 rpm in gear. I run it at 2,800-3,000 rpm cruising speed. Maybe my prop needs adjusting but that seems awful close?
Many tachs read off the alternator so they're actually telling you alt speed not engine speed. And usually the alt spins faster than the engine so it can be way off. Usually there is a calibration screw to adjust it but you need to at least borrow an optical tach to do that. Harbor freight has them fairly cheap, good enough for occasional use.
