Hi Jeffrey,
Do you have photo of boat and engine, I guess if its a F4 its one I will know ??
175 psi is the lower side of good if it has 1 piece head. If its got 2 piece head 175 is good.
Bottom cyl is always a little lower cos the oil pump drive is missing.
Good starting point is timing 19 deg, fuel min 98 oct, main jets 165, carbon reads, 10 mm gap. with 1 piece head.
You can go down jet size but beware dont go much past 19 deg with timming.
2 peice head timing 26 deg fuel min 95 oct main jets 155, 10 mm read gap.
If its running 6j2 2 ring pistons keep eye on piston crowns and land between rings. (6J2 pistons BAD batch of piston, most fail, some still turn up as new old stock ! 6H3 work almost as good)
Try to keep max RPM just under 8000rpm !!!! 7400-7500rpm they run and run and run !
Find a good 11 x 19 or 11x20 prop !!!!!!
Fit head temp gauge. lots problems come from "cold seizing" need to get temp in engine with out cooking it !
Carl
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