Will a different prop work?

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thegooddan

Cadet
Joined
Jan 22, 2011
Messages
6
Here's a new one for a prop expert. I have a 1994 Merc 115 outboard with an aluminum prop. The motor idles great at about 900 rpm. When I put it in gear it will troll at idle speed about 2.85 to 3 mph. What can I do to slow down to about 1.8 mph short of pulling a drift sock or putting a flip-down plate on the motor? Can I put a smaller bladed prop on this motor? If so, where do I find one? I've been told a different pitched blade won't help very much. I don't want to buy a kicker motor to slow down. Thanks
 
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ufm82

Master Chief Petty Officer
Joined
Jul 29, 2003
Messages
827
Re: Will a different prop work?

It's not a new idea but it restricts your abilities while not trolling. You didn't state what pitch you are currently running but you can buy a prop that has less pitch and it will slow your boat down. However you'll lose top speed and can wind up over-revving your engine if you aren't careful. There are a ton of prop selectors out there including one on this site. Find out what you have now and go from there. I'd rather stick with the drift sock or trolling plate as they won't affect your normal operation and will likely be cheaper, especially the sock.
 
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Lyle29464

Lieutenant
Joined
Mar 10, 2009
Messages
1,261
Re: Will a different prop work?

reducing the prop bite by 40% would do the trick. LOL the math might be correct but you really should not do that. Your engine could turn about 8000. I like the other idea's you have. Mybe a 5 gallon bucket full of holes.
 
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steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Will a different prop work?

Is 900 rpm in gear? I think 700 is closer to specs.650-700 in gear.
Assuming 900 in gear and a 19" prop 3 mph indicates 60% slip.
At 700 with a 19" prop assuming 60% slip indicates 2.64
700 w a 12" prop 60% is 1.5.
5250 12" prop 9% = 26 mph.
All this disregards what type/size boat.
So if you don't mind a max speed of 26 you could
use a 12" prop.Just watch the rpm.
I think something like a trolling plate is a better bet.
 
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