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:

Re: Extension Boxes and Set Backs
 

Pat, Spoke To John He Felt Good About Ext. Box, Especialy The 12"...should See Good Results. :D

Re: Extension Boxes and Set Backs
 

MY OPINION :rolleyes: ...is that the notch is an aid to lift the bow...without having to buy an expensive "add on". However...I have found it alone not sufficient on this hull http://img44.exs.cx/img44/4299/tgcemoticon1422oc.gif....thus the additional setback.

Re: Extension Boxes and Set Backs
 

AMEN!

Did I mention the Stellings removes the Merc damper on the flywheel which reduces shock to the outdrive. I am sold on the IMCO just for that fact.

Re: Extension Boxes and Set Backs
 

Bash,
Std hight or 3" rise and stock XR drive????

Re: Extension Boxes and Set Backs
 

It sounds like there are pluses and minuses to the different types of extensions...
Mounting the engine 3" higher sounds to me like it may effect the CG negatively...
Tom,
I am probably repeating my self now, but I think you should talk to Mike (Zuperboat). PM him and ask for his phone #. He can talk boat all day and night just like the rest of us.
The Zuperboat had a neutral Imco box and a -2" short lower.
However, the Zuperboat is lighter than a Y2k...
If your leaning toward the Imco how about this?
Imco neutral box mounted 1" higher than the standard X like Krack's boat.
Then with a stock length drive, the prop would be 1" lower than the Zuperboat was rigged and 1" higher than Krack's boat.
Sounds like a safe compromise... :drink:

Re: Extension Boxes and Set Backs
 

Hmmmm. I gotta mail Mike.

Re: Extension Boxes and Set Backs
 

Lots Of Thoughts Here. We Will See What Happens With Superbabi And 12" Stelling. I Feel John Knows Best What Y2k Needs..........

Re: Extension Boxes and Set Backs
 

Gary,
I don't think John has ever used a Imco from talking to him, but I'm sure they both will work fine. I may be going to 900+ hp if I don't crack 100 this year so I know my idle will be on the high side. I'll need the xtra shock absorbtion of th Imco shaft.

Re: Extension Boxes and Set Backs
 

Tom, 900 Hp. Wow !!!!!!! On An Xr Drive ????

Re: Extension Boxes and Set Backs
 

Gary, 4:48am???
Don't you ever sleep?
I guess when I have another Babi, I won't sleep either... :drink:

Re: Extension Boxes and Set Backs
 

Max Machine Works XR. He's in Havasu where I boat alot. Thier running 1000+ hp in alot of thier Bravo style drives. IT'S ONLY MONEY, RIGHT GARY!!!!! Did you step up to that 1000SCI yet? You should be gettin board with the 600SCI soon. you change motoers more than I change my shorts! :D :evilb: :eek: :drink:

Re: Extension Boxes and Set Backs
 

TOM, YOUR RIGHT, THE HELL WITH THOSE PISTON MOTORS. I'M THINKING TURBINE RIGHT ABOUT NOW. :rolleyes: :D

Re: Extension Boxes and Set Backs
 

I thought so! :D

Re: Extension Boxes and Set Backs
 

:D TOM , LETS ORDER TWO # 6 MERC DRIVES, ONE FOR MY TURBINE, AND ONE FOR YOUR 1000 HP. :rolleyes: :D :evilb:

Re: Extension Boxes and Set Backs
 

Gary,
I did a little reading today about the Stelling 12" extension box.
The box raises the dive 1" in it's neutral position and allows for adjustments of 1" up or 1" down from there. The engine does not have to be moved. Vary cool set up... :cool:
Definitely the way to go if the best prop-shaft depth is not known... :drink:
Tom,
I would have to agree with JC on this one. Too many unknowns; go with the standard X and have some adjustment... :D

Re: Extension Boxes and Set Backs
 

PAT, THANKS MUCH, I CAN'T FIND A WEB SITE FOR STELLINGS. I E-MAILED & PUT A CALL IN . WE WILL SEE WHAT HAPPENS. WE HAVE BEEN DOWN THE SHORE THIS WEEKEND SO I WAS ASKING AROUND ABOUT THE STELLINGS 12" SET BACK AND I HAVE BEEN GETTING VARY POSITIVE ANSWERS !!!!! SO IT LOOKS LIKE A GO WITH THE BIG 12" " S "................... :evilb:

Re: Extension Boxes and Set Backs
 

I did talk to Stellings on thursday. Great guy, nice product. He did say that you would have to remove the Merc driveshaft damper on the flywheel to bolt his ujointed shaft on. Your call Gary.
I think I'll go with the Imco 3" and then do a 1 or 2" drive spacer to get the prop back near stock but still have the ability to go higher by removing the spacer if needed.

Re: Extension Boxes and Set Backs
 

Tom, I Do Hear What You Are Saying. But My Choice At This Point Has Been Narrower Down A Bit. John Has Opened Transom Already. Belive Me I Would Use Merc. Its Steering & Setback If I Could. I Am Not Going To Do Transome Over Again. Thats Why We Are At This Tough Decision Time. I Feel The Stellings Set Back With The Damper Removed Will Really Not Have Any Adverse Effects???? You Know This Was Real Easy On My First Invoice With John, A Simple 496 Ho. Oh Well, Lets See What Happens .....................gary
.

Re: Extension Boxes and Set Backs
 

Hey Tom,
I understand your reasoning for the Imco over the Stellings...
But let me just throw another thought at you:
How about a Neutral Imco box with a short Sportmaster lower on your XR drive mounted at the standard X dim.
This is basically the way MRD rigged the Zuperboat.
With a 750HP blower motor, she ran high 90s and with Mike's 575HP/540 she ran 85-87mph... :drink:
My concern with the Imco +3" box would be raising the engine 3" from the standard...

Re: Extension Boxes and Set Backs
 

From all the chat about balace I've been hearing here, I may just go with a neutral box and stock XR and see how it runs. I just read a email from Zuperboat and I'm thinking he could still use more prop in the water.

Re: Extension Boxes and Set Backs
 

Krak,
Do you know how far below the bottom your prop shaft is?

Re: Extension Boxes and Set Backs
 

Looking at the numbers posted by Krakmeup and fastedy, the stock set-up would seem to be right on... :cool:

Krak's boat: about 72mph @ 5000 with a 26p... :D
Fastedy's boat : about 82mph @ 5000 with a 30p... :D
I don't think you could ask more from a V bottom... :drink:

However, from what jcap has told us, the slip numbers really start to rise as you push a Y2K toward 90mph... :rolleyes:
Professor jcap learned that a 2" spacer and a 5 blade prop gave his boat the added bow lift to crack 90mph. :D
I believe jcap gained 4-5mph from 87 to 91+...

Now how does this all relate to an extension box?
What is the norm; raise the prop 1" or 2" with the 12" extension?

Tom, I like your latest thoughts... :cool:
Mount the engine and drive in the proven location. Add the neutral extension box and that Big Azz 572 and see how she runs! :D :D :D

Re: Extension Boxes and Set Backs
 

Run the Stelling box and then put in my Dyno in it and see just how much power your boat is putting out and you can 'dyno your hull' that is see how much HP/TQ it takes to go a specific MPH.

Re: Extension Boxes and Set Backs
 

Marty,
That sounds like a cool package you have there.

Rick

Re: Extension Boxes and Set Backs
 

In the water on the fly sounds cool!

Re: Extension Boxes and Set Backs
 

To see more do a OSO search for 'on-board-dyno pictures'.

Re: Extension Boxes and Set Backs
 

my y2k did not like the ext box, and boxes often do NOT increase bow lift ,they make the boat longer thus increasing the length of the leaver and push the fulcrum farther back, in fact they increase stern lift, my boat lost bow lift and about 2 mph with a neutral box ,
jim

how many days till spring?

Re: Extension Boxes and Set Backs
 

Alright now I'm confused as HELL! :eek:

Re: Extension Boxes and Set Backs
 

Let's post some results to clarify some of this. Who can list all the 30's that have boxes and results?

The boat 30' Y2k Tempest
OSO name
Hp
setback
rise or std box
prop
speed before
speed after

Re: Extension Boxes and Set Backs
 

6...
But there is still about a foot of snow on top of my boat...:rolleyes:

Good to here from you Jim!
I hope all is well!

Sounds like jcap just may have saved you fellows a bunch of money... :cool:

Tom,
The only other OSO member to talk about an extension box on his 30 is Zuperboat.