speeddemon651

I've come across a slightly used IMCO 12 inch neutral extension box. I called the guys out at Imco in NV to get the big picture on adding it to my boat along with a external hydro steering. First off is anyone else running a Extension box on a 26 Velocity ? I currently have the engine out for a rebuild. Its a 540 with 600- 650 hp range. With the box I was told I should pick up about 8mph. Any input would be appreciated .

Pat McPherson

Good question.
You'll likely need a shorter lower if you add an extension box.
The Velocity race boat, for sale here, does not have a box on it; maybe those guys have some input.
Call Velocity, Steve will tell you what he thinks.
8mph increase sounds like a sales job to me.

speeddemon651

Well at this point I went from a 454 Mag to a 540 with 600 - 650 hp. I'm just trying to get the boat setup to be capable to really fly. About running the extension box in racing I believe its restricted in most classes. Imco did also mention that, but He said I needed to see exactly how low the drive was when parallel to the bottom of the hull. He said that would tell If I needed a shorter lower drive.

Revelocity

A neutral extension box probably won't pick up any speed since the boat already uses a similar affect from the notch transom - your high speed rough water handling may improve however. The IMCO shorty drives coupled with a 5 blade prop seems to offer more speed potential on the twin drive boats then on a single drive.

speeddemon651

I agree, I've done some more research and talked to a guy that has a velocity 260 that runs 113 mph, he said spend the money in the steering and lower and a good prop and don't worry about that box.

Andy

Holly crap 113mph in a 26' boat. Any pix of that boat?

velocitykid

speeddemon, good talking with you yesterday, i see from your post that imco is trying to sell a standoff box. 8 mph increase, if that was the case steve would have one every boat that left the factory, at 113mph if i thought it was worth 1 or2 mph i would have one. no real magic to making one of these boats run, get the x-diminision close within .25in, put in lots of power and learn to drive your boat. the last step is usually the hardest. i will try to post a pic of my ride but im not very good with a computer, just give me a boat and things can happen

Revd Up

What X dimension measurement should you shoot for?

velocitykid

sorry it takes me a while to get back to the computer, i can't find where i wrote the x- diminsion # down for my boat, but a quick and dirty method, on the back of the boat measure from the top of the notch to the bottom of the transom assembly. my measurment is 6", another 260 that i set up with the same engine combo measures 5.75" and is 3mph slower. i am running standard height drives and the boats respond very well to prop work. i have tried moving the x-dim up by .25" and .5" and lost speed because of to much prop slip. i have set up other velocitys with lower x-dim and had no problem getting them into the mid to high 90s with blower power

Revd Up

Thought I'd check mine. From the top of the notch to the bottom of the transom assembly mine also measures 6". Glad to hear I have a good drive height.
Thanks