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I'm past the first 5 hours of breaking in my SE106 on a 78 Searay with a 198 Mercruiser. I tried to bring it up to WOT and only got about 3500 rpm. With the prior drive I would get about 3900. Should I switch to a lower pitch prop? Right now I have a 15-1/4 X15 pitch, Seray's website recommends a 15-3/4 x 17 pitch but I suspect I'd loose even more RPM's. Does it seem reasonable to go to a 14 (or 13) pitch prop? Any suggestions? Thanks
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Prop Size
The westmarine catalog states in general a 2" increase in pitch reduces rpms by 300-400 rpms, just the reverse to increase rpms, 2" decrease in pitch increases rpms about 300-400 rpms.
If you go from a 3 blade to a 4 blade prop and keep the same pitch expect about 50-100 rpm reduction.
Elevation, gas, weight, and other factors all effect WOT rpms.
Find out what your WOT rpm range is, example 4 cylinder gm (4300-4600 rpms). I personally get faster mph if the boat revs to about 4,000 and better fuel economy, but Westmarine and others recommend you do not overprop your boat (puts high load on the engine). I typically run 1500-2800 rpms, with WOT of 4,000 rpms. (gm 4 cylinder 135hp, se 106)
I run a ProPulse 4 blade composite prop that is adjustable from 14-21 pitch (14.5 dia). I have used this prop for 4 years with probably in the range of 500 miles of run time + trolling, all ocean fishing. I have had no problems with the prop and you can fine tune the pitch in 1" increments. I did have a storage unit move the boat with the outdrive down and break a propeller fin, you can buy replacement blades.
Hope this helps, caution WestMarine is expensive so shop around. I did purchase my prop from Westmarine.
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