high RPM's ?

[mwagne30]

O.K. the boat has been a great bonding tool for my son and I. for those that don't know my son(14) and neighbor(70) are fishing partners. I and water don't mix!! but so far the boat thing has been great! The question I have is this I read that the operating rpm is around 4000-4500 and we pull 5000-5500 easy, the prop is factory 14 1/4 x 21 what should I step it up to? top speed is around 45mph. should I go as far as 14 1/4 x 25 to drop it down 800 rpm. The out drive is a volvo sx with a 5.0 carb 190 hp matched to it. now we are not trying to make this a race boat just drop the rpm's, any help is great, and I don't want to sound cheap but I don't want to buy 4-6 props and do the "let's see how this work's" thing thank you I should add boat, 96 Four Winn horizon

 

[steelespike]

Re: high RPM's ?

Not an expert but::
I think I would start by confirming the tach is accurate.and the prop is in good shape.1,000 rpm seems like a lot.You would need a 26" pitch
I don't even remember discussing that kind of pitch in that kind of setup.

 

[mwagne30]

Re: high RPM's ?

Do you think I can use a car Tach, if so we can check that this week and as far as the prop, it's new, from the volvo box

 

[steelespike]

Re: high RPM's ?

I guess a car tach might work.Worth a try.

 

[mwagne30]

Re: high RPM's ?

O.K. I was on craigslist and now have two new props both S.S. one is a 22 and the other is a 24 I will start with the 24 and work down. I also found a used tach and will wire it in tonight . after we looked at the prop on the boat we think it might have been retuned? is that right? if so how knows how good of a job was done. Once we find out what combo we like we will then change over to alum. prop. the kid like's the way these look but the old man tells me that much more damage can be done. so we will only use them for the test. one is still in the box the other was to large for the boat and switched to a 19 for hole shot's.The nice part is this guy is "loaning" them to me for the test.