Re: Only 4500 -4800 RPMS- 90 HP Johnson on 20'SF
Raise it only 1 hole at a time. Bottom of the cavitation plate 1" to 1 1/2" above the keel line is right.
4800 max RPM is too little, and puts extra torque stress on rods and bearings. You end up using more fuel. too.
Start with raising the engine. All that costs is time and sealant for the bolt holes.
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Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.
Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!
Currently without a SeaCraft 
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury
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