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Old 08-30-2012, 05:47 PM   #1
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Question Another prop question

I have a 2002 2700 SCR with a 6.2 MPI Merc Bravo III and originally I had 20 pitch props.
This gave me a good hole shot, but I had to run at 4100-4200 rpm to get 22 knots.
Now I put on 22 pitch and she's sluggish getting out of the hole and I'm running 3800-3900 rpm at 22 knots.

My question is: I've read somewhere about using a 22 pitch for the big prop and a 20 pitch for the small prop.
Does this sound doable?

I'm just looking for a little better hole shot and maybe a few more mph, while keeping a lower rpm.

Thanks!
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Old 08-31-2012, 08:54 AM   #2
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i think you are going the wrong way
max rpm should be about 4700
10 or 20% less is also 10 or 20% less Horsepower = max speed
so if going from 20 -> 22 gives you a downfall of 300 rpm (10%) i would go the other way
try a 19 p and see what it does
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Old 08-31-2012, 01:10 PM   #3
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Bmetro, the best way to really analyze and compare propping is by comparing the Max RPM range of the engine and compare that to the actual RPM"s when at Wide open Throttle (WOT). Don't necessarily look at speed as that can be influenced by sea state, tides and current. The RPM at WOT should be somewhere within the range of the MAx. RPm for the engine. Proper drive trim attitude and trim tab will also have some impact on this.

Going up in pitch will decrease hole shot, but increase cruising speed at a given RPM. Going down in pitch will increase hole shot but decrease cruising speed at a given RPM. If top end is what you're looking for, increase pitch. If hole shot is what you're lookng for, decrease. This is provided that you remain within the Max. RPM range of the engine.

I believe the Max. RPM range for the 6.2L MPI is 4800 - 5200.

As for mixing prop pitches, I'd take a look at the Mercruiser prop calculator as well.
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