21 ft Lowe pontoon

[#onthepontoon]

Hi I purchased a new 21 ft Lowe pontoon with a 90 hrs. 4 stroke comand thrust mercury . It cam with a 4 blade 14 pitch prop. My to speed was 16 mile an hour at 6000 rpm. I talked with dealer he wanted to bring the rpm down and speed up so he got me a 3 blade 15.5 inch 17 pitch prop it brought my speed up to 21mph and rpm down to 4500. When I would try to go faster it would cavitate. He the got me to try a 15 pitch. Now it runs at 4250 doesn't Rev out or cavitate but still 20 mph. Is this the best I'm going to get for speed. And will this pull knee board or a tube maybe a skier now and then. I understand the more people in the pontoon the less it would perform . Any suggestions. Thanks

 

[HotTommy]

I would expect a 21' two log pontoon boat with a 90 HP motor to hit the low 20s with a light load and the engine in its optimum peak RPM range. That's fast enough for simple tubing and lighter skiers on two skis. Pontoon boats don't produce a wake, so wake boarding is not an option. The challenge for tubing is that you'll quickly lose speed if you make sharp turns to make the ride more exciting.

P.S. There's another whole forum here for propeller questions. They might suggest other options to optimize your speed and RPM.