Extension box on a 29
 

I'm sure this topic has come up before, but I have a fairly detailed question.

I have a 1995 29 that came with a stock HP500 carb.
back in 2006, I built the motor with a ProCharger and with a few burnt pistons later finally tuned it to what ran 713 Hp on the dyno and 78 MPH on GPS with a XR upper, std lower and 28" Bravo. Actually got 79.6 twice, but never quite to 80 :(

I took the Proharger off a couple of years back as I was trying to sell the boat, but not having much interest in it, so I redid the interior last year and decided to keep it

I pulled the motor last fall to have a look at the components and freshen her up. Everything seems pretty good, except that the original roller cam has some wear on the flank of#7 exh. So I am replacing it with a bit lumpier unit to see if it'll squeak 750 hp on the dyno.

Never had external steering on it, but I think its time. But have been wondering about either a shorty drive or an extension box with raised X dimenson.

Shorties seem a bit pricey, but according o CP Performance, I can get a Mayfair ext box with add-on dual ram steering for about $4300

Does anyone have any experience with speed numbers and handling before and after with an extension box?

Thanks

Does anyone have any experience with this topic?
Thanks

A good friend of mine had a 1999 29 scarab with a single 502 with a whipple and he tried the stern jack and he only got 1 mph out of it but he did not do the shorty lower unit. Hope this helps

I put a -1 imco on my scarab 22 and it made a big differnce in handling and gained a little in top end, do not have to trim up real high and runs better in the chop. I am running close to 600 hp and i run a 30 labbed bravo 1. I did have to go to a 4 blade when i went with the imco . I do have drew marine sidewinders on the drive to help the chime walking. I have done 82.5 on gps .

Thanks for the feedback guys.
I'm thinking that it would be alot of money and testing of high dollar props to make it right . All that and may only see a couple of MPH!
Will have to ponder the idea some more........

What kind of speeds were you seeing with the stock HP500 without the procharger?

With the stock HP500, it would see as high as 67 in cool spring weather and as low as 63 in the muggy summer heat.
65 average

I would call and talk to someone like IMCO. Tell them what your idea is and what you have. Measure your x-dimension before you call though, cause they will ask. I talked to them when I was looking at putting a shorty on my old boat. They were very helpful.