Loss of RPMs with changed prop

SaltytSal

Seaman Apprentice
Joined
Jun 30, 2006
Messages
32
1997 Evinrude 115 V-4. My original prop was 14 X19-(not Evinrude- probably Michigan Wheel). Recently had to replace this prop and purchased a new BRP/OMC prop. The gentleman who sold me the prop said OMC doesn't make a 14 X 19 prop and the closest is 13.2 X 19. Anyway, with this new prop my top WOT went down from 5400 to 4000 which is a substantial drop!! Where do I start to troubleshoot? Thanks.
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
I'd say with that much of a change either the props aren't marked correctly, or you have other motor issues and its just a coincidence.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Take prop to a prop shop and have it measured, probably has more pitch than was stamped on prop body ? Slight less or more diam with same pitch should not account for 1400 wot rpm difference.

Happy Boating
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
Check the prop to see if they handed you the wrong one. There's no way 2 19" pitch props should have that much difference in rpm one vs. the other.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Check the prop to see if they handed you the wrong one. There's no way 2 19" pitch props should have that much difference in rpm one vs. the other.

+1..... on no way. 14" on a 115 V4? And 19" pitch at that?

My last big OMC was a 125 I bought new in 1972. It had a 12-13" dia prop and 19P (as I recall), 3 blade SST (Stainless Steel Teflon coated). 14" props are for the 150's and up in the Merc line....probably OMC too. When changing props you need to keep it apples and apples; same brand, same model, usually tweaking the pitch at about 200 rpm per inch change, more pitch lowering rpms and less upping them, same number of blades, diameter floats as the pitch changes (in prop design) which is what you tweak....adding a blade requires dropping pitch by an inch or so for same rpms. Something is dreadfully wrong.
 
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