Prop size 1989, Mark cruiser, 3.7,18.9

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
I am trying to figure out when I bought this boat a while ago if I actually bought it with the correct prop size I have a 1989 regal medallion wonderful boat. It was in storage for like 20 years.

It’s running fantastic but I’m just curious what is the proper propeller size for this boat right now I have a J 14.5 with a 19 pitch. Now as a spare, I have a 14.9 with a 21 pitch. Now my understanding is if I put the 21 pitch on it’ll be faster off the line but I’ll lose rpm range. I never really pushed this boat past 3500 RPMs. Now I’ve taken a raptor about 41 miles an hour 42 but I’m not gonna push it. What would change into a 21 pitch do I wanna verify. What are the reasons I want to do this is because my existing profits been hit a few times and I feel it’s causing vibrations which we all know it’s not good you want a smooth prop
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,082
Ayuh,.... The "Right" prop will allow the motor to run at or very near it's stated max rpms,.....
Smaller pitch gives better low end, not bigger,....

Moving this to the prop forum,....
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
13,636
Unless you know what Rpm the motor hits at WOT, you will not know if you are propped correctly. You also need to know what the WOT Rpm Range for your engine is.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
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50,233
Take your current prop, and do a run, 3-5 miles at WOT, then come back the other way document your RPMs and your speeds.

If you are getting 4600-4800 RPM, the 19 pitch prop is correct
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
13,636
Take your current prop, and do a run, 3-5 miles at WOT, then come back the other way document your RPMs and your speeds.

If you are getting 4600-4800 RPM, the 19 pitch prop is correct
In 89, the WOT range might have been 4400-4600
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
Unless you know what Rpm the motor hits at WOT, you will not know if you are propped correctly. You also need to know what the WOT Rpm Range for your engine is.
4200-4600 is what I found out from my boat
 
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