20' bowrider. More blades for better bottom end?

[cube21]

Right now we have a Ballistic, SS, 14 3/4", 17p, 3 blade prop. On a 20' bowrider with a 5L MPI alpha 1.
We hit 5000rpms WOT at around 49mph..ish.
[recommended is 4600-5000]

So, for the most part it does ok, but theres a few things that need to be fixed:

-My dad slaloms, and it takes a little too long to get him out of the water.
-The boat doesnt plane at a slow enough speed for wakeboarding (at least for us beginners).
-Its really difficult to hold steady speeds under 20mph because of the planing issue.

Questions:
Will a 4 blade solve these problems? Or should we look into a 5?
Is there any need for another Stainless prop? or will aluminum be fine?
What pitch and diameter would work best for what we want?

thanks to anyone who knows more about this than me and wants to chime in!
-CUBE-

 

[steelespike]

Re: 20' bowrider. More blades for better bottom end?

A 4 blade in the same pitch should solve all your problems.
Rpm may drop about 100 rpm;I feel your motor is better off at 4800-4900.
The boat should plane easier,stay on plane at less power and diddling.
it may be more responsive around the dock.aluminum will work fine;
I've seen some excellent results here with the Solas Amita.

 

[45Auto]

Re: 20' bowrider. More blades for better bottom end?

You would be better off spending your money on a set of Lenco or Bennett trim tabs. They would plane the boat faster and also allow it to hold a much lower planing speed than any prop ever could.

 

[steelespike]

Re: 20' bowrider. More blades for better bottom end?

Yes trim tabs can be very helpful but too agressive use can cause extra drag.
They do add extra complication you may not want to deal with,maintenance/repair.
I think a prop costs less and assuming you don't chop rocks require little or no maintenance.

 

[cube21]

Re: 20' bowrider. More blades for better bottom end?

We have looked into tabs as well as a tower to help watersports...but we want to start with a new prop before we go into that since we are only using a 3 blade.

thanks for the responses.
-CUBE-

 

[stimps]

Re: 20' bowrider. More blades for better bottom end?

Five blader worked like magic on our four winns. Holds a lower planing speed and holeshot is way better than the three blades props I have. Strangely top speed has not changed a great deal. If you do try trim tabs they can ruin the shape of the wake so pretty much defeat what you are trying to achieve.

 

[Tail_Gunner]

Re: 20' bowrider. More blades for better bottom end?

Right now we have a Ballistic, SS, 14 3/4", 17p, 3 blade prop. On a 20' bowrider with a 5L MPI alpha 1.
We hit 5000rpms WOT at around 49mph..ish.
[recommended is 4600-5000]

So, for the most part it does ok, but theres a few things that need to be fixed:

-My dad slaloms, and it takes a little too long to get him out of the water.
-The boat doesnt plane at a slow enough speed for wakeboarding (at least for us beginners).
-Its really difficult to hold steady speeds under 20mph because of the planing issue.

Questions:
Will a 4 blade solve these problems? Or should we look into a 5?
Is there any need for another Stainless prop? or will aluminum be fine?
What pitch and diameter would work best for what we want?

thanks to anyone who knows more about this than me and wants to chime in!
-CUBE-

260 hp in a 20' boat...Your speed seems a bit light. How many people are you running with the above numbers...That is important along with your gear ratio it should be on the outdrive and are those gps speeds or just the boats speedo

While i have no experience with that prop...There are some that dont think much of it..

 

[cube21]

Re: 20' bowrider. More blades for better bottom end?

260 hp in a 20' boat...Your speed seems a bit light. How many people are you running with the above numbers...That is important along with your gear ratio it should be on the outdrive and are those gps speeds or just the boats speedo

While i have no experience with that prop...There are some that dont think much of it..

That speed is with 5 people plus all gear in the boat, not glassy water either.
But remember the prop is pitched at 17, so I assume the speed is about right.

I think were going to a 4 blade Solas Amita, Ill post on the improvements when we get to it.

edit - Im surprised people arent happy with it being that its nearly a $400 dollar prop.

 

[Tail_Gunner]

Re: 20' bowrider. More blades for better bottom end?

http://www.go-fast.com/Prop_Slip_Calculator.htm

Heres some thoughts..It can be dissapointing to spend money and not achieve the desired results...Now the above link will aid you in making a decision in your prop selection. A 1.62 final drive ration is fairly common in a boat of your size with a v8...and you show almost no slip...so something is amiss..The ratio should be stamped on the side of the out drive..

It can be annoying but if you could post your speed using a gps it would be very informative...one side note...your tach on the back of it there is a small switch that should give you three setting's...4..6..8...make sure its set to 8...You will need a flash light

 

[cube21]

Re: 20' bowrider. More blades for better bottom end?

Well I didnt check the tach setting or gear ratio...
but we just got our Solas Amita 4 blade 17p in the mail, so well put it on and Ill let you know the results.

thanks for the advice guys.
Ill keep you posted.

-CUBE-