Extension Boxes and Set Backs
 

Ok Guys,
We have been talking about Extension boxes and Set backs a lot lately.
I need to be enlightened a bit more on how they work as I almost pulled the trigger on one yesterday... :eek:
From what I gather, the idea is to get the propeller into "cleaner" water and to add leverage that will help raise the bow... :cool:
I can understand how a full length V bottom like my boat may benefit from moving the prop back.
But how effective are extension boxes on boats that have a notched transom like a Y2K. Is not the notch for the same reason?
Superbash is running with an 18" set back on his out board 24' that also has a notched transom.
There has to be more to it... :rolleyes:

Re: Extension Boxes and Set Backs
 

Well the setback will increase the effect that the notch has going already. Almost like moving your notch farther forward, so to speak.
Your just moving the pivot point farther forward of the hull so it takes less weight or leverage to lift the bow, so that means less trim up and more forward propulsion.
Tom

Re: Extension Boxes and Set Backs
 

Tom, Your Getting 12" Stelling. Talk To Me ?????

Re: Extension Boxes and Set Backs
 

I originally wanted the Imco stock hight and just raise the x-dimension 1". It also has a torsion shaft extension which helps absorb some of the shock of a high idleing engine when put in gear. JC likes the Stelling which is adjustable 3"s I believe. I don't know at this point if it has a similar shaft or just a regular extention. JC also wants to raise the drive the full 3"s which I'm a little nervous about since hereing other horor stories of drives too high and loosing speed.

Re: Extension Boxes and Set Backs
 

I did read some were that the Stellings extension box is adjustable...
I wonder how that works??? Another U-joint???
Sounds like the way to dial in a boat to me... :cool:

Re: Extension Boxes and Set Backs
 

The engine will have to be raised up or down with the change you make in the box hight. So it's not as easy as it sounds but at least your not stuck with a set X and can't do anything about it like Imco or MERC ITS.

Re: Extension Boxes and Set Backs
 

Somebody on the Excalibur link refitted a 30?'er, and a friend was doing a 40'er, and they called Reggie Fountain for advice. They went into X-dimensions, extensions, etc. I think the bottom line was that a notch negates the neccessity of an extension. Fountain didn't find a significant change by adding a box to their notched boat.

Re: Extension Boxes and Set Backs
 

I've never seen an application that went negative unless the drive was too high or too low. Get it right and it's a good thing, either speed or better handling/ride.

Re: Extension Boxes and Set Backs
 

Just to clarify a couple of things. With the Stellings box you can raise 2"s without raising the engine. He uses ujoints to allow this. $2450 dealer cost. Is it worth it?
The Imco is fixed at 0 or 3" raise. $1600

Re: Extension Boxes and Set Backs
 

On My $20,000 boat, probably not.
On your $100,000 boat, absolutely! :drink: