H190SS Merc 4.3L Alpha Prop Suggestion?

WildH · **Posted:** Wed Jul 06, 2016 9:18 am

Put a couple small dings in my alum prop that came with the boat. Looking for a replacement. Any suggestions?

Stock prop was 14.5 19P. I had no problem with it. I noticed that there is a fair amount of variance in diameter when looking for 14.25 vs 14.5 vs 15.25 etc. Does that make a major difference? Also, do I need to do anything different from alum to SS?

Any input would be appreciated....brand, specs, etc. Just looking for a good all around prop for cruising and towing a tube.

GottWhat · **Posted:** Wed Jul 06, 2016 9:31 am

Diameter, pitch, number of blades and metal-type all make a difference in RPM. Each engine has a recommended RPM range during wide open throttle. You want to be within the middle area of that range. Below the range and you are over-propped and above the RPM range you are under-propped.

Going up in diameter and/or pitch will lower the RPM. Going down in diameter and/or pitch will raise the RPM. Changing blade count from 3- to 4-blades will lower the RPM. Going from AL to SS could slightly lower the RPM.

There are guides out there that will go in depth with estimated RPM changes depending on diameter, pitch, etc. I highly recommend researching multiple sites before making a choice. OR you could keep things simple and with what came with the boat new.

WildH · **Posted:** Wed Jul 06, 2016 10:00 am

GottWhat wrote:

Diameter, pitch, number of blades and metal-type all make a difference in RPM. Each engine has a recommended RPM range during wide open throttle. You want to be within the middle area of that range. Below the range and you are over-propped and above the RPM range you are under-propped.

Going up in diameter and/or pitch will lower the RPM. Going down in diameter and/or pitch will raise the RPM. Changing blade count from 3- to 4-blades will lower the RPM. Going from AL to SS could slightly lower the RPM.

There are guides out there that will go in depth with estimated RPM changes depending on diameter, pitch, etc. I highly recommend researching multiple sites before making a choice. OR you could keep things simple and with what came with the boat new.

Very helpful. Thanks. These were all things that were randomly in my head but know confirmed. Do think sticking with the same diameter and pitch but going to stainless would be OK? I can't imagine the rpm changing significantly with that transition.

GottWhat · **Posted:** Wed Jul 06, 2016 10:12 am

WildH wrote:

Very helpful. Thanks. These were all things that were randomly in my head but know confirmed. Do think sticking with the same diameter and pitch but going to stainless would be OK? I can't imagine the rpm changing significantly with that transition.

Going from 14.5 to 14.25 diameter might be enough to compensate for the difference in metals. I recommend doing some research to confirm.

With that said, I was happy with the Michigan Wheel Apollo (stainless) I installed on our last boat.

GottWhat wrote:

I also replaced the prop. Went from a SS 14.25 x 23p to a SS 14 x 21p and love it. The issue with the 14.25 x 23p was it appeared to be over-propped with top speed coming at 4200-4400 RPM. The new prop has the same top speed but comes around 4800 RPM, right where it is supposed to be. The hole-shot is much improved as well. Plus it looks nice and shiny.

WildH · **Posted:** Wed Jul 06, 2016 6:01 pm

Thanks. I was looking at the Michigan brand ballistic. Need to do some research. Found a screaming deal on a 14.25" 19p Stiletto Adv 2. $125 new.... Only problem was it was for a Johnson evinrude.

Iboats had a blurp on ss vs alum. They said a half inch either way makes little differenceb but not sure if go up and keep the same pitch. That would seem a big step in addition to ss.

www.iFourWinns.com

H190SS Merc 4.3L Alpha Prop Suggestion?

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