Stupid Question

[sportsnut87]

New boater, I have a 175 searay with a merc 3.0 130 horse motor. Currently have a 21 degree prop on it,(i hope I am saying that correctly), What is the best number I should be looking for, so the boat performance at its best, Hole shot and top end, no skiers yet, but tubing ect. I current get about 42 to 44 mph with the boat with 3 adult males in it(well as adult as 3 guys can get on a boat)

 

[rndn]

Re: Stupid Question

The most important part of propping a boat is what rpm's are you reaching at wide open throttle (WOT)?

 

[Silvertip]

Re: Stupid Question

The question you asked has a number of considerations so answers are hard to come by. You need to understand that top speed and hole shot are mutually exclusive. You need to compromise on that. If you want top speed, you need a prop that provides top speed. If you want to do water sports, you need a prop for power. If you drive a stick shift car you know you can't climb a real steep hill in high gear so you downshift. The same thing applies to a boat but you don't have a transmission -- you have only one gear so it must do both (get out of the hole and perform at high speed) hence the "compromise".

You currently have a prop with 21 inches of pitch -- not 21 degrees of pitch. That's part of what we need to know. You now need to make sure the engine is properly tuned. Then put an average load in the boat and make some wide open throttle runs noting rpm and speed. Make several runs. Then get back to us. I think you will find the 21P is about right for top end but it will not likely work very well for skiing/wakeboarding/towing.

 

[matthewpa]

Re: Stupid Question

So 42-44 is WOT. You certainly don't always run at that speed and if you do you will have a short lived 3.0L 130hp motor. I have a very similiar boat and the 21p prop is too much. I have knocked mine down to a 19p with outstanding results.
There is now magic prop that is going to give you a great hole shot and top end. You need to make a choice what is more important. I would not get too caught up in top end, the only way you get that is by WOT, see second sentance in 1st paragraph. There are several really good websites to check out like www.mercurypropellers.com, www.turningpointpropellers, etc...