Tritoon speed verses rpm

[jckelope]

So i just purchased a 25ft party barge tritoon with a merc 150 verado. I was doing 28mph and 3500 rpm at wot. The motor is rated for up to 6400 rpm. It actually has a great take off but seems it should go a little faster at wot. What i dont understand is the low rpm. If i understand props. I would think going to a lower pitch prop would raise my rpm but also lower my speed? Is that correct? Is their a way to prop it so as to increase rpm and gain speed or should i just live with what i have?

 

[airshot]

As your rpm increases, so will your speed to some degree. Due to slippage there is not a direct corolation between speed and rpm. Think of it as changing the gear ratio in your vehicle. Pontoons are more challenging to calculate due to excess drag in the water. If you have a prop shop in your area, talk to the experts..

 

[rallyart]

In your case lowering the pitch would allow you a faster takeoff AND likely raise your top speed. Top speed is limited by horsepower being produced and at 3500 rpm you are probably a long way below your peak horsepower so you can't push the boat faster through the water. Getting your engine up towards its peak power will give you more extra power to increase the speed.

 

[jlh3rd]

you're at WOT and 3500 rpm? It's not the speed of the boat you should be concerned about, it's your motor. Your lugging it excessively.
you need to prop that motor to get it into recommended operating range, then let the speed be what it's going to be....

 

[Scott06]

So i just purchased a 25ft party barge tritoon with a merc 150 verado. I was doing 28mph and 3500 rpm at wot. The motor is rated for up to 6400 rpm. It actually has a great take off but seems it should go a little faster at wot. What i dont understand is the low rpm. If i understand props. I would think going to a lower pitch prop would raise my rpm but also lower my speed? Is that correct? Is their a way to prop it so as to increase rpm and gain speed or should i just live with what i have?

Have you verified tach is accurate at 3500 rpm with a shop tach? If you have good hole shot one would think that you are not so over propped you are 3 k low on WOT RPM....

Verify the rpm first then if accurate you need to go way down in pitch. So far down (13" less than now....) it doesn't add up unless you have the wrong gear case on the motor , hence why I am thinking tach is wonky

 

[flashback]

Might be you need a tune-up, otherwise your over propped.