Quiet Storm

Has anyone tried a pair of IMCO shorties on a 386 with extension boxes before? I was told my X dimension is too low with the boxes and the shorties would help.

NJSONIC

Quiet Storm,
I have Shorties on my 386 but no boxes. They seem to work well. I gained 3mph over the stock case.

Quiet Storm

Did it change the ride of the boat? Mine wants to porpoise between 40 - 45 mph in flat water. I thought the higher X dimension may change this.

hpoffshore

Hey QS,
The porpoising in flat water is more a function of bottom design and prop spec than X dim. Many coventional bottom boats(Sonics and other brands as well)will exhibit that behavior in flat water. Things like blade rake/pitch/rotation will have a greater effect than just drive height. It's over-simplified, but that bouncing comes from a hull that's not staying completely "on plane". A prop with more stern lift might help or might just change the speed range where it happens. Of course these changes can really affect your top-end,too. You also didn't say wether-or-not the drive is fully negative trimmed when that happens. It's easier to prevent the bouncing from starting(negative trim at those speeds), than to stop it once it started.
Hugh

Quiet Storm

Hugh
I know I mentioned the porpoising but that's not that big of a deal to me. Putting the tabs down or speeding up takes care of that issue. I'm also happy with the speed of my boat so a couple mph faster, although nice, isn't why I'm considering the shorties.
The real reason is I have broken my XR drives a couple of times and I know the previous owner broke them too. One of the people that repaired them for me said that I may benefit from the shorties. Not only with speed but raising the X dimension may help the drives live longer. It would take some of the strain off them. What do you think?

Thanks
Roger

hpoffshore

Interesting idea....it's been my experience that the majority of stress comes from the planing process, especially with the 575's in bigger hulls. The torque curve must be real fat, right around the rpm where the hull is getting ready to plane off, and the props are just hooking-up. If you raise the prop height, you'll probably need a little more prop diameter so the boat won't become a bear to plane off.
Hugh

Quiet Storm

I'm running 32p Bravo 1's and they bring it up on plane without any problems now. I bring it up easy to save the drives but I also can feel if I push it to hard the props would break loose. I was thinking a set of 5 blade props may be the answer.

NJSONIC, Did you have to change props when you put the shorties on?

NJSONIC

Quiet Storm,
When Doller Offshore was dialing in our boat for Sonic they started with B1's 28 pitch to 32 pitch. with the standard drive,they then changed to the shorties and went with Hydromotive P-5X's in a 30 pitch. I have to be very easy on the throttles to get it up on plane but after that watch out. I'm also running 1.36 gears. With the B1's we were running 1.5 gears and kept hitting red line at 75% throttle.