I'm stumped, need advice.
Posted: Tue Jul 04, 2017 9:06 pm
Hello everyone,
I just put a bigger motor on my 24' pontoon. I bought a 2001 Yamaha 150 HPDI. (2 Stroke)
The prop is 15 1/4 x 15 ML Stainless.
At WOT I can't get passed 4400 rpm @ 22kts (25mph) measured by GPS. I'm expecting 35kts with a 150hp.
The motor is running smooth as glass, it accelerates like a dragster, throws you back into the seat, gets to 4400 rpm in about 5 seconds, but it won't get above 4400rpm. Redline is 5500 RPM. While at 4400rpm the engine very smooth and not bogging.
The motor has only 300 hours, and ran with no problems on the previous boat.
In the driveway and WOT, the throttle is at the stops under the cowling.
Spark plugs are brand new, previous plugs indicated perfect combustion.
If the 15 pitch prop is too fine, wouldn't I be hitting redline?
If the 15 pitch prop is too course, acceleration would be bad, but it's like a rocket.
If fuel starvation was the problem, wouldn't the engine be running rough at 4400 rpm?
I'm stumped why I can't get more speed/power. Your thoughts?
I just put a bigger motor on my 24' pontoon. I bought a 2001 Yamaha 150 HPDI. (2 Stroke)
The prop is 15 1/4 x 15 ML Stainless.
At WOT I can't get passed 4400 rpm @ 22kts (25mph) measured by GPS. I'm expecting 35kts with a 150hp.
The motor is running smooth as glass, it accelerates like a dragster, throws you back into the seat, gets to 4400 rpm in about 5 seconds, but it won't get above 4400rpm. Redline is 5500 RPM. While at 4400rpm the engine very smooth and not bogging.
The motor has only 300 hours, and ran with no problems on the previous boat.
In the driveway and WOT, the throttle is at the stops under the cowling.
Spark plugs are brand new, previous plugs indicated perfect combustion.
If the 15 pitch prop is too fine, wouldn't I be hitting redline?
If the 15 pitch prop is too course, acceleration would be bad, but it's like a rocket.
If fuel starvation was the problem, wouldn't the engine be running rough at 4400 rpm?
I'm stumped why I can't get more speed/power. Your thoughts?