Prop selection for merc 15hp kicker

[flobbest]

Just bought my first Lake Erie boat, a 2003 25' Triton 2486 WA and also purchased a used (2002) 15 hp merc 4 stoke kicker motor for trolling. I noticed that the prop wables (shaft is not bent) so I am looking to replace the prop. It is a "A12 9P" can't find any specs on line so I don't know what that # means but my question is, should I just replace with same prop or is there a better choice for my trolling application ie; 4 blade, different pitch, etc.? Thanks.....Frank.

 

[Silvertip]

Re: Prop selection for merc 15hp kicker

There is a sticky at the very top of this forum titled READ THIS FIRST. We can't tell you you need until you tell us how what you have actually performs. There are lots of props available. All have different applications and will perform differently on different boats. Until we know how the one you have performs on your boat, we can't help much since there is no performance base line. Of particular interest is wide open throttle -- observed -- not what the manufacturer suggests. Those are the two numbers we will compare to figure out if what you have is already correct.

 

[steelespike]

Re: Prop selection for merc 15hp kicker

Just bought my first Lake Erie boat, a 2003 25' Triton 2486 WA and also purchased a used (2002) 15 hp merc 4 stoke kicker motor for trolling. I noticed that the prop wables (shaft is not bent) so I am looking to replace the prop. It is a "A12 9P" can't find any specs on line so I don't know what that # means but my question is, should I just replace with same prop or is there a better choice for my trolling application ie; 4 blade, different pitch, etc.? Thanks.....Frank.

Being a kicker used mostly for trolling we priobably don't need a lot of performance specs.
I believe that is a 9" pitch prop. In your setup I would think a 8 or 7" would be better also a 4 blade would give you better control.

 

[Silvertip]

Re: Prop selection for merc 15hp kicker

On a Lake Erie you better have the kicker propped correctly. It may mean the difference between getting back to the dock ahead of a storm or not should the big engine take a dump. A prop that is wrong at WOT is wrong throughout the rpm band. The only time I would recommend a prop with signficantly less pitch (than the one you have if that is correct) would be to slow the boat if idle speed cannot produce the slowest speed you need for trolling. But that means you over rev on the top end. The other extreme would be if the engine over revs at wot then an increase in pitch is required. If you need to add lots of throttle to maintain your desired trolling speed and the rpm annoys you, you need a bigger motor. More pitch in that case only lugs the little motor. Since a big boat relationship to a little motor is akin to a workboat, a four blade prop with lots of blade area in say an 8 pitch might be ideal. However, without WOT rpm data this is again a crap shoot. Any prop you choose will probably work. The effect on the engine is what is being ignored with those uninformed choices.

 

[flobbest]

Re: Prop selection for merc 15hp kicker

Thanks for the input genltemen. I don't have any performance data on the current prop because I just bought the boat and am in the process of rigging it (adding the kicker etc.). I guess I could wait to run it and see how the prop performs but as I mentioned, it wobbles on the shaft and is actually rubbing the lower unit housing. I just thought maybe someone had already been there done that and could just say what prop would be best for trolling. Thanks again.....Frank.

FWIW, I posted this identical question on "walleye.com" on March 15th and so far there have been 31 views but no replies. iboats rocks!!

 

[ondarvr]

Re: Prop selection for merc 15hp kicker

Which model 15 Merc is it, the standard model or the high thrust Bigfoot?

 

[flobbest]

Re: Prop selection for merc 15hp kicker

Good point, I should have mentioned that it is the standard, not the hi thruster or "big foot" unit. Thanks.