Home › Forum › Ask A Member › 1959 Evinrude 18HP has power, moves water but…. › Re: 1959 Evinrude 18HP has power, moves water but….
Hmmmm, You say your 9.9 sits much lower in the water. Is your 9.9 a long shaft motor? Is it possible you have a 20" transom on your boat? The "short shaft" 18s of this era have a shaft length of about 18". Kind of a "mid length" shaft and would be too short for a long shaft transom. If that is the situation, cavitation could most definitely be your problem. Maybe just as the boat begins to plane it’s lifting the prop too close to the surface and it cavitation. The anti cavitation plate should be nearly even with the bottom of the boat when mounted to the transom. Say +/- about 1".
Measure your boat’s transom. If it measures very close to 20" from top to bottom and your 18hp doesn’t have the long shaft spacer in the tower, I think we found your problem. If your transomom measures close to 15", then I suspect the prop is spun.
-Ben
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