will moving the x dimension up 3 inches wtih an 12 inch extension box reduce porpoising?

That would sort of depend on what your prop shaft height ended up being after you factor in the ideal angle or attack, set-back, and X-dimension and what style props you end up with. But in theory, since you are moving the point of thrust further back from your C/G and fulcrum point, use of your trim will have much more effect than before. --- Jer

Wouldn't it depend on what was causing the porpoising?

Correct, Payton. But that's the best I could do with the info. given. I'm kind of assuming that if he has a 42 Cig as his signature would indicate, there probably aren't any serious hull issues. --- Jer

well it seems all revolutions seem to have a porpoising problem from what i ahve heard. its a triple engine. triple 600 horse. once we get to about 70 and attempt to raise the drives up just 1/10 and it porpoises like crazy. bravo ones with nose cones. it is the stock x dimension from factory. is there a certain place the propshaft should be in relation to the bottom of the hull? idont no where the drive should be in this application. i am not sure if it needs to be lower or higher. it woud be great if someoen could help wiht explaining where ideal height is. thanks

also, is there nething to chekc about the hull...check for a hook or rocker?

I had a brand new Wellcraft Spyder years ago which actually pulled to one side. It had a concave hook on the port and a convex bulge on the stbd. It would always list and pull to the port. It was eventually determined that it was popped out of the mold prematurely. The boat on smooth water looked like a guy walking with one leg 3 inches shorter than the other. If you were turning stbd it would porpoise out of control. To the port it was like having the trim tab buried.

I have read several of these threads where the prop guys are trying to fix these conditions with props, others with extension boxes and x dimensions.

The boats that seem to have the most problems are several years of a couple models of Cigs, 42's and TG's. The best approach in my opinion is to initially address the possibility that the hulls are not true. The problem is getting somebody who knows their stuff and have them show you.

If you have read some of the threads these guys have spent 1000's and it may improve the ride but it truly does not fix it. They have masked the situation but the issue remains.

I am one of those guy's that spent thousands on my 38' Top Gun until we removed a hook which I couldn't even find with my 8' straight edge. We first raised our drives ,lost a ton of speed and she ran more like flipper than before.We tried Hydro 4 blade props, my boat likes 4 blade Bravos. We finally lowered our drives 1/2" more than stock which also helped quite a bit prior to fixing our hull. There really is know instant fix to this problem, I would start with the hull and work your way up . Good Luck!

thanks for the responses. well check the hull with a straightedge next time we go down,I know that the boat has sat awhile on a trailer(i think 2 years before we bought it,and over a year now while restoring, and has only been in water twiced for a matter of hours during that time) and before that had sunk and i guess musta been pulled outta water with a crane. i guess something may have happened to put pressure on the hull in either of those situations.does anyone know how high the drives should be, like where should the propshaft be in relation to the hull when in neutral trim.?
thanks