Need Help Choosing a New Prop

Bulbash

Petty Officer 1st Class
Joined
May 22, 2012
Messages
332
Boat: Bayliner Capri 1750 with OMC 2.3 Cobra

Currently I have 3 blade 13.5 x 15 prop installed on it, it does give me a good hole shot but not much of top speed around 30 -35mph. RPM's stay in recommended range (5200 - 5400).

Now I'm planning to upgrade to 4 blade prop, and question is which pitch should I go with? Should I stay with 15 pitch or should I go to 17. As far as I understand, my hole shot will improve, but top speed will decrease so would it make sense to increase to 17 to keep same top speed or no?
 

dazk14

Ensign
Joined
Jul 22, 2008
Messages
966
Re: Need Help Choosing a New Prop

What are you trying to "fix" with the new propeller.
 

Levinz11

Senior Chief Petty Officer
Joined
Apr 1, 2012
Messages
726
Re: Need Help Choosing a New Prop

Going to a 4 blade will help your holeshot... usually. It will also LOWER your top speed a few MPH... usually. I use a 4 blade because I am always pulling something: tube, knee board, wakeboard, etc. For watersports a 4 blade is great. When you go from 3 blades to 4, you need to DROP an inch of pitch or 2.

If your goal is more speed keep the 3 blade.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Need Help Choosing a New Prop

I'm guessing that when new it probably had a 17" prop turning around 5400 and speeds about 38.
But I think she has gotten tired.I don't think there is anyplace to go for more speed.
You might be sure the throttle opens all the way.Check/set the timing and be sure it advances as it should.
A compression check may tell you about the motor.
The same prop in stainless might help a little
 

Bulbash

Petty Officer 1st Class
Joined
May 22, 2012
Messages
332
Re: Need Help Choosing a New Prop

You might be sure the throttle opens all the way.Check/set the timing and be sure it advances as it should.
A compression check may tell you about the motor.
The same prop in stainless might help a little

Boat runs great and has a newly rebuild engine...

What are you trying to "fix" with the new propeller.

What I'm trying to find out is, what will happen if I go from 15 pitch 3 blade prop to 17pitch 4 blade...
 

BoatDrinksQ5

Petty Officer 1st Class
Joined
Feb 11, 2012
Messages
377
Re: Need Help Choosing a New Prop

from my limited knowledge adding another blade and increasing pitch will make the RPM's change outside of the recommended range (likely anyhow)

Typical practice assuming existing 3-blade falls in proper RPM range (your case), then you drop pitch with a 4blade.
 

Levinz11

Senior Chief Petty Officer
Joined
Apr 1, 2012
Messages
726
Re: Need Help Choosing a New Prop

Boat runs great and has a newly rebuild engine...



What I'm trying to find out is, what will happen if I go from 15 pitch 3 blade prop to 17pitch 4 blade...

You will lose about 600 RPM's at WOT and speed as well.
 
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