Need prop change

jcupo6

Chief Petty Officer
Joined
Jul 13, 2009
Messages
512
I recently changed motors. The boat had a 140hp mercruiser with a cracked block. I replaced it with a 120hp merc but kept the same prop, couldn't afford to purchase a new one at the time. I'm ready now!

1. Looking for a good overall prop to gain some speed and rpms. I mainly use the boat for fishing, but might pull a tube here and there.
2. Currently the boat has a 19 pitch aluminum merc prop. Sorry, I'm not sure what model. It's pretty old but in good condition, maybe a black max?
3. The boat currently tops out between 26-30 mph at 2900-3000 rpm with an average load. She should be running around 3800-4400 rpms.
4. Engine is a 1978-1982 120hp merc with a 1 year old SEI drive.
5. Boat is a Aluminum 22 foot 1973 Starcraft Holiday. With no fuel, gear, or passengers the boat weighs around 1600 pounds. I usually run with 1-2 passengers.

Since the current prop was installed for the 140hp motor, I assume I can get more rpm's and speed with a prop change. Thanks in advance for your help!
 

jcupo6

Chief Petty Officer
Joined
Jul 13, 2009
Messages
512
Re: Need prop change

I would also like your opinions on aluminum vs stainless props. I generally do all my boating in the Delaware bay, not in waters with rock bottoms.
 

jdub2

Cadet
Joined
Jul 12, 2010
Messages
16
Re: Need prop change

Assuming the engine is in top running condition, I'd go down in pitch. Maybe to a 15" pitch. Should gain, in theory, around 800rpm (200 rpm increase per inch of pitch decrease)
 
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