Re: Overpropped; What to do?
Your 4JHE should have come with a 17x12 two blade.
That's based on a Hull speed should be 8 knts, not 7 (LWL = 35).
3240 rpm (90% of max) / 2.17 reduction x 12 (pitch, inches) with comes out to 1493 feet per minute.
Once you figure the slippage (per David Gerr's chart) at 48% you get 776 feet per minute  just under 8kts (810 feet per minute).
It's important to note that Gerr's slip chart is an ESTIMATE  so you get some variation in numbers.
Okay, that's what you should have had, now you have a 3 blade of unknown pitch
You can get a pretty good estimate on your pitch by reverse engineering the speed/rpm:
Since you are saying you are going at 1800 rpm, that means you have a shaft rotation of 829 RPM and are moving 708 feet per minute (7 kts).
That comes out to a pitch of almost 20 (829 * 20 (pitch) *.52 (slippage) / 12 (convert feet to inch) = 718 feet per minute
That's a bit much in pitch and explains why you can't get 90% of max RPM.
I'm running the same engine on my Irwin 38  with a 16 inch 3 blade MaxProp, pitch set to 12.
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