Questions on extension boxes.
 

I have been thinking of installing extension boxes on my Advantage Sportcat. Not for a speed increase, the boats plenty fast, but to be able to bring the drives up into the full trailer position. Let me explain. The drives on the boat are currently very high. So when I put them into the full up position they can only come up so high before they would touch the swin platform. Because they do not come up like a normal drive would, the bullets of the lowers will drag in the sand when pulling onto a sand bar. Doesn't sound like much, but it can be a PITA when they are dragging and there is a current(we boat on the Colorado river).

So here is my real question. If I were to install an extension box with a +2 to 3 inches, do the motors have to be raised? One shop said that with a +3 IMCO it would.
I appreciate any help guys.

PS Are any boxes available with a lift and do not require the engines to be mounted higher?

Darrell.

Darrell,
Typically a 12" setback will put the drive 3" deeper in the water when at speed. So yes the drive needs to be moved up 3". Using the Imco boxes, both need to have the motor raised. The straight one would be equivelent to what ever height you mounted the box. Ex: move the box up 3" to raise the drive height 3" and the motor goes up 3".
With the 3" offset box.. you can mount the box where your drive is now and the drive ends up 3" higher, and yes the motor has to come up 3". Imco uses a torsion type driveshaft that has to be in line with the engine. Imco retains the rubber coupler on the flywheel.. eaiser on the drive.

Stellings uses a drive shaft that has ujoints on each end and is bolted directly to the flywheel. Their box can be mounted higher without moving the engine. But there is a limit, I dont think you can move it the full 3". All depends on the drive shaft angle. The stellings box is also adjustable, I think it has 2" of up and down movement. But the cutout in the transom needs to be modified if you move it up too much..
I have an Imco and not 100% sure on the Stellings info, others can chime in to verify or not.

Hope that helps.
Dick

Mr Gadgets
 

Are you using a +3" or standard IMCO box on your Checkmate? Are you using a shorty or std. lower drive?
Thanks.

MR Gadgets,
Thanks for the info. Really, the only way for me to do it, would be to go with standard ext boxes and -2 lowers. More than I want to spend at this time. Once again, thanks for the info.


Darrell.

Your welcome Darrell! Glad it helped.

Dick