1991 246 WA engine height

“Hi.

For the past year, I have been the happy owner of a 1991 246 WA powered by a 1996 Yamaha 250 Saltwater Series (pre-OX66). The engine has a relatively new powerhead and lower unit, so I’m planning to keep it for a bit but would like to make sure it’s set up correctly to give the best possible performance, especially since it was not the factory engine (I’m guessing it came with a Merc but don’t really know). I have a number of questions but am starting with the engine height.

The engine has 1 hole below the bolt (I believe this means it can go up one hole) and a prior owner installed a wedge. She porpoises at speeds under 40 mph unless the engine is trimmed all the way down, and porpoises more with a couple folks sitting on the aft bench. At WOT I see around 45mph (I’ve seen up to 48 when it’s just me and she’s totally empty) and can tilt the engine as high as the two rams will get it without ventilating (so long as I’m running straight. this can’t be efficient as I’m throwing a 4 foot rooster tail but she doesn’t lose any speed when it’s tilted that way). In addition, when trimmed normally I can’t see the anti-ventilation plate. I assume that all of this means the engine’s too low – Does anyone with experience on these particular boats know if this sounds to be the case? Does anyone know which hole the Yamaha should be in, and is it possible that it has to come up farther than the one available hole? If it has to come up farther, would a manual jackplate with a 6″” setback (the least i can find) work?

Any other suggestions or information would be great. Thanks.

Graham”