I have a 25 ft pontoon boat with a 80hp yamaha four-stroke engine. What is the best prop for maximizing mph. Also, what type of speed should I be getting and what is a good rpm to run it at consistantly. Sorry I am new to the outboard engines and do not know these things.
If you read the stickies at the top of the page and the helps at the prop store page I think
you will see what we are up against trying to select a prop for a boat.
However if you give us some info we should be able to tell if your setup is working as it should
and make suggestions of what changes may be needed.
If you get us your present prop size( on the barrel or under the prop nut).Something like
13 X 13 (diameter X pitch)your present max rpm and speed lightly loaded. and your typical load and activities.
There is no "best" rpm to run an outboard at. If you need to run wide open run it. If you want to cruise, run at whatever cruise speed you want. If you want to putt along, do it. The critical rpm however, is determined by the prop you select. The prop must allow the engine to be able to reach the manufacturers recommended wide open throttle RPM with what YOU consider and average load. If the engine cannot reach that rpm it is lugging and serious damage can occur. Obviously if the engine revs over the upper limit then that's not good. You need to go to the Yamaha web site, look at performance bulletins, select your engine, select the boat type (pontoon) and then select the make. If you don't find a test report for your make and model pontoon, select one that is close in size. The performance report will indicate speed, fuel consumption, prop type and even it's part number. You can't do any better than that unless you have access to many different props and lots of time to do WOT testing.