had same prob
I have a 5.5 osprey that had a 90 2 stroke, I also struggled to plane whilst loaded up. I recently fitted a 115hp 2 stroke Suzuki, still tows great, performs great, I don't think it's over fast, infact the best way to explain is boat & machine in perfect harmony with each other, I'm very happy now, hope this is of any help to you.
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