"I installed a 2YM15 recently,
"I installed a 2YM15 recently, with the 3.2 to 1 reduction gear. In calm water, in gear, my full-throttle maximum rpm is 2900, which is 76% of the maximum (intermittent, not continuous) rpm for this motor (3830 on my tach).
"John" the diesel guru tells me that I should get a maximum rpm of about 3450 under load, under way, which is about 90% of the no-load max of 3830. He says I need to get my prop re-pitched so that my engine is turning about 550 rpm faster at full-throttle (3450 - 2900 = 550).
When the prop is adjusted, John says I should cruise at about 2800 rpm which is about 80% of 3450. He says until my prop is fixed, I should cruise at 2300 rpm which is about 80% of my current maximum loaded rpm of 2900.
QUESTIONS:
1. Does John know what he is talking about? If not, what are reasonable numbers?
2. At full throttle now, I can run for hours without overheating, at somewhat more than my theoretical hull-speed. Is the engine really working too hard if it is not overheating?
3. As John mentioned, until I get my prop fixed, I should cruise at about 80% of my current max. rpm, which is 2300. If I can reach my hull-speed and not over-work the motor, why should I worry about changing my prop pitch?
THANKS!
Notes: My sailboat is 28' and 9500 lbs, with a full-length keel. Hull is clean. Prop is a 14x11 3-blade "Campbell Sailor". I sized the prop with the prop calculator at boatdiesel.com and with the manufacturer's input."
"I installed a 2YM15 recently, with the 3.2 to 1 reduction gear. In calm water, in gear, my full-throttle maximum rpm is 2900, which is 76% of the maximum (intermittent, not continuous) rpm for this motor (3830 on my tach).
"John" the diesel guru tells me that I should get a maximum rpm of about 3450 under load, under way, which is about 90% of the no-load max of 3830. He says I need to get my prop re-pitched so that my engine is turning about 550 rpm faster at full-throttle (3450 - 2900 = 550).
When the prop is adjusted, John says I should cruise at about 2800 rpm which is about 80% of 3450. He says until my prop is fixed, I should cruise at 2300 rpm which is about 80% of my current maximum loaded rpm of 2900.
QUESTIONS:
1. Does John know what he is talking about? If not, what are reasonable numbers?
2. At full throttle now, I can run for hours without overheating, at somewhat more than my theoretical hull-speed. Is the engine really working too hard if it is not overheating?
3. As John mentioned, until I get my prop fixed, I should cruise at about 80% of my current max. rpm, which is 2300. If I can reach my hull-speed and not over-work the motor, why should I worry about changing my prop pitch?
THANKS!
Notes: My sailboat is 28' and 9500 lbs, with a full-length keel. Hull is clean. Prop is a 14x11 3-blade "Campbell Sailor". I sized the prop with the prop calculator at boatdiesel.com and with the manufacturer's input."