prop

[pies]

hi everyone, i am new to boating and new to the forums. i am hoping some can steer me in the right direction. i have recently bought a 17 foot tracker boat with an 1985 inline 4 cylinder mercury. i am told that the egine is a 50 horse. the prop on the engine is a 10 1/8 th with a 15 degree pitch. the serial number of the engine is A702319. this boat has really poor power off the start and has a hard time getting up to plane. i put new plugs in it and it runs really good and smooth. can anyone tell me by the serial number is this a 50 horse and is this the right prop for this boat and engine . many thanks inadvance.

 

[Barnacle_Bill]

Re: prop

Yes its a 50hp. As for the prop you need to know what RPMs you are turning at WOT.

 

[Moody Blue]

Re: prop

Well pies you could change to a lower pitch prop (13" perhaps) but without a tach you run the risk of over revving the motor. The lower pitch will help out of the hole but you will loose a little top end speed. Your existing prop is 10 1/8" diam x 15" pitch (not degree).

 

[pies]

Re: prop

when i run the boat i can not get the rpm's above 5000. and it takes a long time to get it up there. and the top speed is about 24 mph. thanks very much for the replies. i have read alot of other posts, all you guy's are reallygreat and helpful.

 

[Moody Blue]

Re: prop

You can generally assume that for each 1" change in pitch the rpm's will change by 200. Reduce the pitch by 1" and rpm's will go up by about 200. Looks like the 13" pitch prop should do it for you. Better hole shot for sure. Have you tried adjusting the trim angle of the motor once on plane ? Might be able to get a few more rpm's and MPH out of it.

 

[pies]

Re: prop

thanks RodC , i am going to try a 13 inch pitch this weekend. how much will it affect it if i go to a larger diameter prop. like if i tried an 11 inch with a 13 inch pitch.

 

[walleyehed]

Re: prop

The diameter is built to suit the pitch-a factor we don't need to be concerned with in this application, but as a general rule, the diameter goes up as pitch goes down.

 

[timmathis]

Re: prop

I don't think that you will get much more than 24 MPH out of that 50 H.P. I think it is doing pretty well

 

[pies]

Re: prop

i am not worried so much about the speed as i am getting it to plane out. with 2 guys and fishing gear it takes alot to get this boat up on plane. thanks for the help so far.