Prop Size

wakedad1 · Addict Joined: 19 Sep 2003 Posts: 667 City: Discovery Bay

I have a Maxum with a 330 hp black scorpion v-drive. This thing revs too high. If I was to leave it wide open for any length of time it would probably hit 6000 rpm and blow up. Right now it has an Oj 14x18 prop and at about 3/4 throttle is hitting 5200 rpm and 42 MPH the most I ever pushed it to was like 5500 rpm and 44 mph and that still was not wide open. When it's wieghted usually about 1000lbs ballast plus 5 or 6 people the rpm's are running around 3200 @ 22.5 mph. Should I stick with the low top end and good hole shot or get a higher pitched prop?

jonsmith2340 · Soul Rider Joined: 02 Feb 2005 Posts: 370

What is more important to you... do you really need to go over 44 mph? IMO I would rather have the extra low end torque, on the chance that I have extra people/weight in the boat, so that I still have good hole shot versus geting a couple extra top end. But that's for me on a small lake. If you are on a big lake where you need to travel any distance to check out which bay is calm the top end might be more important in the interest of saving travel time.

wakedad1 · Addict Joined: 19 Sep 2003 Posts: 667 City: Discovery Bay

jonsmith2340, I do like having all the low end power but I was wondering if it might be too much low end or if there might be something slipping in the v-drive causing it to over rev????

jonsmith2340 · Soul Rider Joined: 02 Feb 2005 Posts: 370

I don't know how to answer that one. I don't know how to check the slip in a tranny (v-drive).

The only way I can think of to get to that would be to use the gear ratio of the v-drive and calculate the rpm's of the prop at like 5200 motor rpms. With some math you should be able to calculate the speed the boat should travel with a specific pitch prop. The asumption in this is that you have no slip of the prop, which is invalid, and brings us right back to your question. So hopefully someone else can help with that.... hint... that way we can both learn something!