prop question on 2012 Mercury 40 hp 4 stroke

dwatson1

Cadet
Joined
Feb 13, 2014
Messages
6
2013 Bass Tracker Pro 165
2012 Mercury 40ELPT 4Stroke EFI
prop 10 1/2 x 13 black max

Right now at full throttle the rpm will hit around 6200 and reach about 31 mph. This is too many rpms and I never run it that high. I usually keep it at 3/4 throttle and the rpms are around 5600. I have considered changing to a 14 or 15 pitch prop. Either sticking with Black Max or going to a Spitfire. Has anyone with a similar setup have a larger prop. The current 13 pitch prop was on the boat at the time of purchase.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Factory delivered props on light applications usually produces near or top wot rpm factory stated. What are the MIN-MAX wot numbers for that engine ? Does rev limiter is kicking in ? If wot numbers are near your actual 6.2 K, stay with that prop, just throttle less...It's good to have full engine power with engine running safely throughout the whole throttle range.

Happy Boating
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Assuming that your numbers are accurate your wot slip is 18%,a little high.
The 13 isn't wrong, should give a strong hole shot and you can just watch the rpm.
A 14" Spitfire 4 blade should retain a strong hole shot and put the rpm closer to 6000
and should get the slip a little lower.
Other 4 blade improvements may be smoother operation,stay on plane easier art reduced throttle,
and better responce around the dock.
 
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