Mercruiser 3.0 prop suggestions.

Rouletista

Cadet
Joined
May 30, 2023
Messages
6
Hi all. I have a 2000 party barge 22 regency with the 3.0 Mercruiser. I am running a 15x15p prop right now. WOT is 4200 @ 21mph. I was wanting suggestions on if I should go down in pitch to get more on the higher end of the rpm range. Maybe a 16 diameter and less pitch? Any suggestions would be appreciated. Thanks!
 

airshot

Rear Admiral
Joined
Jul 22, 2008
Messages
4,466
Is the engine running up to par, check that first. Is your rpm figured with a light load or a heavy load ? Many folks get the prop setup with a light load at max rpm rating so they don't bog down when loaded. If you always carry a heavy load then prop accordingly. Rule of thumb is...one inch of pitch gains/ looses 200 rpm, where one inch in diameter changes the rpm 100 rpm. Other things like cupping and rake can also make a difference. If you have a prop repair shop near you, use their expertise...
 

St1ngr4y

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Mar 16, 2021
Messages
5
More diameter will make the RPM's go down so that would not make any sense. The party barge seems like a boat that will be heavy loaded. I would suggest a 4 blade prop with smaller dia and pitch to reach the max rated WOT with a low load.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
Messages
47,783
make sure the motor is up to snuff:
  • check compression
  • check fuel pressure
  • check timing
if all is good with the motor, then look at dropping down 1-2" in pitch. if you add a blade, you need to drop pitch. I personally would not recommend a 4-blade prop on a pontoon.

FWIW, pontoons are displacement hulls. it would go just as fast with a 40hp outboard as it does with the 130hp I/O
 

Scott06

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Joined
Apr 20, 2014
Messages
5,740
Hi all. I have a 2000 party barge 22 regency with the 3.0 Mercruiser. I am running a 15x15p prop right now. WOT is 4200 @ 21mph. I was wanting suggestions on if I should go down in pitch to get more on the higher end of the rpm range. Maybe a 16 diameter and less pitch? Any suggestions would be appreciated. Thanks!
yes down in pitch dont sweat the diameter if staying with same type of prop.

make sure engine is in good shape as suggested. Probably a 13" will get you into 4500-4600 range which will put less strain on the engine. Are you currently running a basic aluminum Black Max type ?
 

Rouletista

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Joined
May 30, 2023
Messages
6
I currently have the prop that was on the boat when I bought it. It is a Solas rubex 9511-150-15. Would it be best to go with a black max that doesn’t have the rubex hub style prop that I currently have?
 

Rouletista

Cadet
Joined
May 30, 2023
Messages
6
yes down in pitch dont sweat the diameter if staying with same type of prop.

make sure engine is in good shape as suggested. Probably a 13" will get you into 4500-4600 range which will put less strain on the engine. Are you currently running a basic aluminum Black Max type ?
I currently have the prop that was on the boat when I bought it. It is a Solas rubex 9511-150-15. Would it be best to go with a black max that doesn’t have the rubex hub style prop that I currently have?
 

Scott06

Vice Admiral
Joined
Apr 20, 2014
Messages
5,740
I currently have the prop that was on the boat when I bought it. It is a Solas rubex 9511-150-15. Would it be best to go with a black max that doesn’t have the rubex hub style prop that I currently have?
No that is fine, more or less equivalent to a Black Max from Merc. Everybody used to use rubber hubs for decades until swapping over to the insert style hard plastic (delrin). You are fine with what you have. If your engine is in good shape drop to a 13 and you are done.
 
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