Exhaust Hole Spacing BBC vs SBC
 

I know of two fellow boaters that are considering re-powering with the new 320HP/6.2 small block rather than reworking or replacing 330HP/7.4 big blocks.

How different is the exhaust spacing? Will some off-set pieces need to be added to line up to the holes in the transom?

Going from big blocks to small blocks!!!. What are they smoking? Forget the Hp numbers. Boats work on torque. And the cost must be amazing. Unless they are very small boats why lose the cubic inches.

Well, one of the boats is an older 29' Formula and the owner has heard that that boat will be much better balanced with small blocks, and defiantly faster.

As for the new 6.2 vs. a low output 7.4; I can say that I have run side by side with a fellow that has the same boat as me. He has the 320HP/6.2MPI, I have a 310HP/7.4MPI... He goes right by me. I am thinking that new 6.2 has just as much torque.

I plan to add a little more juice to my 7.4 this winter, so next year should be different...

better balanced I would agree with. I dont have any experience with the 6.2 so I shouldnt have shot my mouth off. I just have found that when you repower a boat, the bigger you go the better because you will want it to go faster in 2 years.

Pat,
For alot less money he could have two custom marine 383's built totaling an easy, turnkey and reliable 750 hp. And lets not forget the 700 lb weight savings over the twin bigs.
Bob

700lbs? Got some aluminum in those babies? I thought it was about 200lbs each...
I would agree that the 6.2 is pricey new, 8K+, but in classifies on OSO, 5K can buy one...
Can anyone answer my exhaust question???

Pat,
Sorry. Added the 350 twice! Call it 400 total.

PAT, BB HOLES ARE UP AND OUT AROUND 2 INCHES FROM SB HOLES. I UPGRADED FROM SB TO BB AND HAD MY OLD HOLES FILLED IN AND RECUT WITH JUST THE TRANSOM PAINTED ($300). THERE IS A DIAGRAM IN MERCRUISER MANUAL THAT SHOWS THE DIFFERENT CUT LOCATIONS,HOPE THIS HELPS.

Not enough weight differance. to out weigh the tourqe diff.I would stay with the big blocks. the 330 are good motors Just up grade to rectangle port heads and buy rebuild kits with a little better cam and have over 400 hp.

I dont know the diff >its sound like you allready made your mind up on the sb.
Good luck
Rob

I bet you could find some one to swap .Somebody wanting to up grade to big blocks. Remember The small block exhaust and tail pipes are smaller.

this a big block install on the same boat that I have

http://images.traderonline.com/img/6...55773606_2.jpg

and here is my install on a Small block I dont see much differance, I do have EMI THUNDERS W/ CORSA Q&Q II

This is a far apart and high as you can go on this boat
otherwise the tips flange will not sit flat

Ha, The 6.2 mpi is a much better motor than the 7.4L . The torque numbers are not that great on the 7.4. No you do not just want to put square port heads on the 7.4. The 7.4 lack of power also is because it is only a 8.5 : 1 compression ratio. If anything put 110cc oval port heads to raise the compression ratio to 9.0:1 and do not run anymore rpm's than stock because you will break that cast crank. The 6.2 mpi is a better motor than the 7.4.