Best prop for my boat ?

[Swordsman]

i too got this wakeboarding bug im sure you all have
started wakeboarding about 3 monthz ago and getting pretty good i think
my boat isnt a wakeboarding boat but it fast enough for begginners
reaches about 18-19mph, lately i feel like i need to get more speed out of it, the question is how ?
so i read a little about the prop and its affects
also made me noticed that my 115HP Mercury 4S EFI, doesnt reach its max RPM
as the specs says its max RPM is between 5800-6400
i have never reached this RPM, full throttle gets me about 5000-5200, and it was like this since i bought it(3 yrs ago)
im not sure whats the size of my current prop, i will check and post it here, but basically what do i need to get more out of my engine, a bigger/smaller prop ?
sorry for the newb question but the diameter refers to the size of the prop right ?
and the pitch ? what is that ?
thank you for your help...

 

[rallyart]

Re: Best prop for my boat ?

You could ask that the Moderators move this to the prop section but the core of it is that you need a lower pitch prop than you have. The diameter is one of the dimensions on a prop. The shaft size is another. Number of blades makes a difference. The cup or curve on a blade makes a difference. However the pitch is the biggest change in performance. It's like the gear ratio on a car.
A 17" pitch moves 17" through the water in one revolution. A 22" moves 22 inches forward. If your engine is running right and the boat is trimmed correctly but you still are not in the maximum RPM range at wide open throttle you need to go down in pitch. Then the engine will spin faster and the boat will accelerate better and might even have a higher top speed.
Usually the size of the prop refers to the pitch rather than the diameter in most situations.

 

[Swordsman]

Re: Best prop for my boat ?

wouldnt a smaller pitch accelerate faster but would come in the expense of maximum speed ?
max speed is more important to me than acceleration...

 

[86 century]

Re: Best prop for my boat ?

It is possible that dropping in pitch your eng will rev higher thus reaching a higher top end speed.

If you are riding at 18-19 now how fast do you think you need to go.
I ride at 18+/- as do most of the people I know. The pro's ride up around 22-23.

Would think most outboard boats wouldn't have much wake that fast.

 

[rallyart]

Re: Best prop for my boat ?

Swordsman, you are 1000 RPM away from your optimum range so you can gain speed by dropping the pitch because the engine will be closer to it's best power which means you will have the power to push the boat faster. Some prop shops will allow you to buy a prop and try several until you find the best one for your boat.

 

[Swordsman]

Re: Best prop for my boat ?

It is possible that dropping in pitch your eng will rev higher thus reaching a higher top end speed.

If you are riding at 18-19 now how fast do you think you need to go.
I ride at 18+/- as do most of the people I know. The pro's ride up around 22-23.

Would think most outboard boats wouldn't have much wake that fast.

two things, first my engine should be able to reach its max rpm for whatever reason isnt it ?
second, its not all about speed
till now when i was wakeboarding, to get a bigger with less white splashed wake i had to trim my engine out as much as i could, that sunk the back of the boat into the water, thus creating a bigger and better looking wake, but the downside is when i was doing this it crippled my usual max speed cause it would 100% plane, so if i could get just a few more mph with the same size of wake it would be absolute perfect

 

[Swordsman]

Re: Best prop for my boat ?

Swordsman, you are 1000 RPM away from your optimum range so you can gain speed by dropping the pitch because the engine will be closer to it's best power which means you will have the power to push the boat faster. Some prop shops will allow you to buy a prop and try several until you find the best one for your boat.

maybe my english isnt good enough so im not sure what you mean by higher/lower pitch, is there a graphic explanation i could understand it better?

 

[Swordsman]

Re: Best prop for my boat ?

never mind about the pitch, went to a mechanic to ask about it and he explained just fine
anyways
i was at the marina today, checked my prop specs
and this was engraved on the side
48 77340A45 13P
what does the number mean exactly ?
i guess 13 is the pitch ? how smaller do i have to go ?

 

[jestor68]

Re: Best prop for my boat ?

A Merc 115 with a 13 pitch at 5200 rpm equals 28 mph (theoretical). Your 19 mph equals 32% slip.

Maybe it would go faster if you trimmed it down (from full up trim) when not wake boarding.

What kind of boat do you have; a cabin cruiser?

 

[86 century]

Re: Best prop for my boat ?

Getting bit by the wakeboard bug can be frustrating at times.
Your are trying to make a boat do something it was not designed to do not that its not possible you may haft to give up some top speed to get what you want.

A bow lifting prop with the right pitch to put your eng in it Max hp range at boarding speed will do wanders for your wake.
With an added bonus of being easier to hold at speed.

 

[Swordsman]

Re: Best prop for my boat ?

Getting bit by the wakeboard bug can be frustrating at times.
Your are trying to make a boat do something it was not designed to do not that its not possible you may haft to give up some top speed to get what you want.

A bow lifting prop with the right pitch to put your eng in it Max hp range at boarding speed will do wanders for your wake.
With an added bonus of being easier to hold at speed.

what is a bow lifting prop ?