Extension Box help.

[tfarmer]

Hello. I need some help. Im looking to add a 12" extension box
and I have a few questions. First.. what is the difference between a imco, stellings, and mercury boxes?
I can't even find one to buy. Who sells them? I need everything
to do the complete install. Cash in hand.
Thanks Timmy.

[JasonSmith]

Imco makes a nice box as does Stellings.
I use Imco because their design uses the coupler from Merc. I think it provides a little more protection to the engine that without.
Imco also uses a torsional drive shaft & Stellings uses a straight driveshaft with universal joints.
In the Baja community, we have found that a 3" rise box yeilds the best results with a stock length drive.

[fast22]

The way that they set the x-dimension is the major difference between the imco and the stellings. The stellings can be raised in the box without moving the motor mounts. With the imco you have to raise the motor. I don't know a lot about the mercury. I think CPperformace carries them and a few others on the board, if you do a search you will find tons of info on them and probably someone who knows a little more than me!

[fast22]

I have the Imco also, no complaints yet.

[f311fr1]

The Imco does use a longer torsional shaft to insert into the Merc coupler. Retaining the coupler helps to save the drive. As stated above the Stellings removes the coupler from the flywheel and hard bolts a u joint to the flywheel into a carrier bearing in the box then a double u joint. Imco does make a netural box so that you do not have to raise the engine, how ever the drive will be too deep in the water. One solution to this would be to run an Imco 2" shorter lower gearcase.

[Inspector]

Fast22, what configuration is your 29', single or twin? Did you use the +3 box (es)? What benefits have you experienced since the installation?
Thanks.

[DiamondPerformance]

We sell IMCO, nice Box,the torsional shaft does help out in saving your drive. Let me know if i can be of any help.

[Wild Card 09]

The Imco is very simple and straightforward, and the shaft and coupler do help to protect drive and motor from abuse. The raised box compensates for the extension into deeper water, and frees up the boat a little, too.

I have run two seasons with the box and it has functioned perfectly, improving the rough water performance to an amazing degree. It has also contributed to top speed, trim and steering response.

I chose the Imco over the Stellngs because the idea of another two u-joints and a bearing carrier seemed like potential trouble, and the raising the x by doglegging this propshaft a source of vibration.
With everything in one line, using a raised front motor mounts (the rear one are ittegral on the Imco raised x box) there is little to go wrong.
The fine tuning of the x is then done with a shorty and/or spacers.

[fast22]

Inspector,
It's a single and have the nuetral 12" box. As stated above my drive is too deep. It helped alot in the rough water and handeling is improved but my x-dimension was not great to start off with, -2" shorty is the next move!

[billet marine]

I have a great, used IMCO standard offset box w/ torsional shaft and steering "wings". Send me a message for details.
The IMCO setup also requires use of "full Hyd" steering. (No room for a tiller arm...)
Thanks, Curtis @ Billet Marine