Propeller for Merc. 50 HP 4 stroke

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briangeorge

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Jun 15, 2010
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26
I have a new smoker craft 16 foot fishing boat with a 50 HP 4 stroke outboard. It has a 10 and 3/8 diameter by 13 pitch propeller. It is very slow out of the hole and even slower with 3 Adults on board. Maximum RPM is around the 5000 to 5100 mark. I have been told by some other boaters that I should be running a 10.5 to 12 pitch propeller to get the full RPM out of this engine. Mercury specs say top RPM on this engine is 5500 to 6000 RPM which I have never seen. Anyone know if the lower pitch prop is going to help?
Thanks and regards:
briangeorge
 
Silvertip

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,762
Re: Propeller for Merc. 50 HP 4 stroke

One inch of pitch down is only going to gain you 150 - 200 rpm and I seriously doubt you need to go lower anyway. an 11 pitch puts you in pontoon boat category. I think there is something else going on. Either the tach is set incorrectly or is simply inaccurate, or there is something wrong with the engine -- such as the throttle not opening fully. A 13P prop is pretty much standard for engines and boats such as yours and it should run in the low - mid 30's for speed depending on load. You need to post some wide open throttle speeds as well as rpm for us to make any prop related determinations.
 
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briangeorge

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Re: Propeller for Merc. 50 HP 4 stroke

Top Speed is usually around 28 mph and max. RPM is around the 5000. As you load more weight as I said (3 Adults) it takes forever to get on plane and it requires lots of trim adjustment to get there. When I am in the boat alone it is still slow to get up on plane but not as bad as 3 adults. Boat has the plane tabs (smart tabs) which did help some.
briangeorge
 
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RicMic

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May 14, 2010
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Re: Propeller for Merc. 50 HP 4 stroke

How much does that boat weigh?
 
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briangeorge

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Re: Propeller for Merc. 50 HP 4 stroke

RicMic:
According to Smoker craft brochure the boats weighs 1010 lbs.
I was in to see Dealer this morning and he has ordered me a new prop. The prop that came with the boat was a 10 and 3/8 diameter with a 13 pitch. He ordered me a 12 inch diameter with a 10.5 pitch. He feels this will make a world of difference.
Thanks briangeorge
 
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RicMic

Chief Petty Officer
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May 14, 2010
Messages
431
Re: Propeller for Merc. 50 HP 4 stroke

I think with weight and load the 12" pitch is probably the right prop, I just don't see it making a "world of difference" from the same prop with a 13" pitch. Let us know what happens!:confused:
 
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briangeorge

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Jun 15, 2010
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Re: Propeller for Merc. 50 HP 4 stroke

The pitch of the new propeller is 10.5 not 12.
The diameter of the new prop is 12".
Hope it works. He figures it should get my RPM up in the 5600-5800 range.
Thanks.
briangeorge
 
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