Extensionbox questions !

[alfons]

Originally Posted by irishtornado

There's no adjustment in a IMCO box you have to raise your engine 3"

The box have a built in 3" raise !

[alfons]

Originally Posted by fast22

Didn't know that, I had a stellings so the box was adjustable. Maybe try moving it up 3" and use spacers in the drive to find the right height?
Scott

How high was your propshaft with the box ? Improvements ? (scarab 29 whipple ! tell me more ! )

[jdub]

Originally Posted by alfons

No i am not going to raise the engine ! i am thinking of the imco-box with 3 inch lift .

With the Imco 3" box you have to raise the engine. The drive shaft they provide is longer and solid. It will not allow for the extreme angle. That is why you MUST raise the engine to align your driveshaft.

Going back 12" and up 3" will most likely net you a 2 1/8" rise. You lose aprox. 7/8" for every 12" depending on transom angle.

You might want to do the motor mods first then the box to see the best results. Doing everything at once will be hard to tell what worked and how much. Or what didn't work and what to change.

[fast22]

I never really had time to play with prop height. I was having drive failure about every two trips or so. Boat is very heavy for a single and 750flbs of toruqe from a blower motor and no rubber coupler didn't work well. I can tell you that the box had no rise, it was set nuetral and had a stock length bravo. I actually gained speed when the box was taken off. I have heard that the 29's like a shorty, you are the first I've spoken to that actually tried it. If you are getting those numbers with a stock 496 then you should be fairly close with your x-dim. These boats need good power to get them going fast. Another thing you may want to look into is hook in the hull, I know mine has a good bit You can see it just by looking, you don't need a straight edge. There is speed to be gained there without engine mods. Alfons are planning the -3" box and the imco shorty?

[alfons]

Originally Posted by jdub

With the Imco 3" box you have to raise the engine. The drive shaft they provide is longer and solid. It will not allow for the extreme angle. That is why you MUST raise the engine to align your driveshaft.

Going back 12" and up 3" will most likely net you a 2 1/8" rise. You lose aprox. 7/8" for every 12" depending on transom angle.

You might want to do the motor mods first then the box to see the best results. Doing everything at once will be hard to tell what worked and how much. Or what didn't work and what to change.

You are so right !! Of course i have to raise the engine. But thats a small jobb compare to "rebuild" the transom ! I will try the box before the engine modifications !

[alfons]

I have heard that the 29's like a shorty, you are the first I've spoken to that actually tried it. I gained 6 mph with the -3 " shorty .

[Irishtornado]

Originally Posted by alfons

No i am not going to raise the engine ! i am thinking of the imco-box with 3 inch lift .

How did this work out?

[fireboatpilot]

I don't think he grasped the fact that he HAD to raise the engine in order to install the box. I think he thought he could do it later after he installed the box and tried it first.

[alfons]

I have now raised the engine and mounted the box/drive !! Looks good :-) Now i just have to wait for the summer :-( F..k winter its about -10 celsius and a lot of snow !