New guy with a prop question

[sivlersnake]

Hello everyone! While my wife and I have had a lot of boats, a week ago we bought our first ponton boat. It is a 2001 20' Sylvan with a 2001 Mercury 75hp 2 cycle. When we bought the boat it was in good shape. We Still have spent a lot of time over the past week we have did a lot of fixing of a lot of little stuff. The only big issue we have left to figure out is the correct prop. I was hoping to get some good input and opinions on what the best prop and pitch would be. What came on the boat was, what I've been told, is a beat up 19 pitch Michigan wheel. The prop had a dime sized chip out of it and the shape was a little beat up. The boat ran 21mpg at 4600 rpm. I should be turning around 5200 rpm. The prop I am thinking about is a 15 or 17 pitch Mercury spitfire with 13" diameter. Any thoughts? While I am good with bass boat props, I am out of my element with a pontoon boat.

[RcgTexas]

First Welcome to the asylum!


19 inch pitch sounds a bit much. 4600 Rpms if WOT is indicative of too much load.

[sivlersnake]

Thanks! Got any recommendations for what prop I should try?

[justrfb]

Hello and welcome...

I used Mercury's own prop selector assistance...

https://www.mercurymarine.com/en/us/pro ... #/step-one

Good luck.

Sincerely,
Rich

[Scott1]

Got to propgods.com and send Ken all the information that you can, he will help you.
The biggest thing is knowing what prop was on it and what your RPM's were at WOT.

[sivlersnake]

Thanks, folks! !

[Seon]

Not on a Merc but on my Yamaha 115hp 4 stroke with a 13.5" x 19 pitch at WOT was 4800rpm where it should be at or near 6K.

A prop shop and a Yamaha dealer told me that the difference for every pitch size, the motor wills gain/lose 200 rpm so I re-propped to a 13 pitch and attained the 6K rpm.

Was also told that it didn't matter what type of boat the motor was on as long as it reaches near or at the manufacturers WOT rpm.

BTW, it was also mentioned that changing from one pitch to another doesn't necessarily mean the boat will go any faster or slower.

[Scott1]

Not on a Merc but on my Yamaha 115hp 4 stroke with a 13.5" x 19 pitch at WOT was 4800rpm where it should be at or near 6K.

A prop shop and a Yamaha dealer told me that the difference for every pitch size, the motor wills gain/lose 200 rpm so I re-propped to a 13 pitch and attained the 6K rpm.

Was also told that it didn't matter what type of boat the motor was on as long as it reaches near or at the manufacturers WOT rpm.

BTW, it was also mentioned that changing from one pitch to another doesn't necessarily mean the boat will go any faster or slower.

Well, just by understanding what pitch means, example, if your boat can turn a higher pitch prop at the proper WOT rpm, it has to be going faster. Pitch is how far the boat (or prop) will move forward in one rotation. 15P is 15 inches, 17P is 17 inches, so yes you will be going faster. Of course that is theoretical and you have slip involved. Obviously if you over pitch and you cannot reach your rpm's, then yes, you could go slower.

[Littlehoe]

115 yamaha here i was at 5000rpm with a 15 pitch 4 blade spitfire @25mph , put on a 13 pitch 3 blade stainless and was at 5700rpm @27mph. This weekend I have a 13 pitch spitfire 4 blade to try. I will let you know what I find out on monday...