I know they can....what i need to know is there a big size difference? Currently the cig in question has the mercII setup with TRS's.......wants ALOT more power and i'm thinking we need to change trannies to the Velvet drives.....question is how much of a difference between the two? Barely much room infront of engine to move it forward......

Add about 4 inches. That is approx. how far you will need to move the engine forward.

I've run 400-450HP small blocks thru stock MercII's in race conditions no problem. You can add 1-2 forward clutch plaes to increase that to about 500HP.

Can they be built to handle 650hp???

I think so. I had mine rebuilt with the extra clutch plate, and the input shaft clearanced.

I think you would be ok as long as you took good care of them. Adding an extra cool helps. More capacity of fluid and cooling ability.

Wally, I think another weak link is the pump gear. My old boat was in that hp range and that is what broke.

Ok....so extra clutch plates and check out the pump gear/possibly make new stronger one if need be....cool! anything else anyone wants to add about weakness in this trans?