propeller question for 1992 50 hp mariner

[skypony38]

what propeller pitch etct. would you guys reccomend putting on a 1992 mariner 50 hp. pushing a 24' pontoon?

 

[ThomW]

That's a tough one to answer with what you have provided. Is there a prop on the motor right now? The diameter of the prop can not change, as is fits the prop shaft for that motor. You can only play with the pitch to adjust your rpm's and performance. What is the model of the motor? The ideal pitch for your prop would be based on what you are getting for RPM's at WOT with the prop compared to your engine's specs on its allowable WOT rpm's. For each inch you change the pitch up or down, you will lose or gain about 200 rpm's, depending on if the pitch increases or decreases. You need to know the motor's recommended max RPM's, then see what the prop you have is giving you for rpm's on the pontoon at WOT. Then you can go up or down in pitch to get as close to the max RPM's as you would like. I know this might not be much help, but without knowing more, its hard to guess what pitch will work for you set up. Cheers!

 

[82rude]

24 foot pontoon fairly big for a 50 just taking a wild guees and thats all it is id say somewheres in the range of 7 or 9 p.I would get a 7 and go from there,see what the rpm,s look like etc.

 

[skypony38]

Thank you sir. Not out to break speed records or anything it's just used for fishing . I'll install an rpm gauge and go from there following your advice. The pic is the numbers on the prop that is currently on it. Items fairly low rpms . Came inform fishing on a nuclear power lake and those jokers lowered the water level so low I messed my prop up trying to load my boat up. It was so low I couldn't even get to the peer. Luckily I had my fold up ramp on there to unload my dad who was in a wheel chair . It was so bad when I backed the trailer in it knocked out the tail lights on the traile from scraping the bottom of the lake

 

[skypony38]

Couldn't get the pic to upload

 

[skypony38]

Prop numbers are as follows;
48 73136 A40 13P

 

[82rude]

I HAD A 60 MARINER OF SAME VINTAGE WITH A 16 FOOT BOAT AND IM SURE I USED A 13P.I would think with a 50hp you would need all the prop pitch you could get meaning a much lower pitch like a 7 or 8.Test with what you have if you can and get back with numbers.YOU have a 13p right now which seems too much for a 24 foot pontoon.

 

[skypony38]

Thank you sir will do

 

[ThomW]

Let us know how it goes. Like I said before, if you are at a 13 pitch now, each inch you drop the pitch, you will gain approximately 200 rpm's at WOT. Just make sure you know what the engine's max rpm's are, and don't go above that trying to get too much from the boat! Good luck and sorry to hear about the low lake!

 

[Sea Rider]

This -,+ 200 wot rpm lose or gain is not cast on stone, it's no rocket science either. Will depend entirely on what's powering what. On light to medium applications will achieve more/less rpm going 1 pitch less/more, on very heavy applications around what's stated.

Why do you think that on portable to medium HP-OB's you can play with pitches in 1 increment/decrement while on the higher HP-OB's with 2 fixed pitches. There are virtually no 1 pitch fixed sizes to play with. If being an exquisit boater will need to send prop to a prop shop for a repitch if in need to fine tune exact max wot rpms as loaded.

Happy Boating