I have a 2005 Y2K that I’m upgrading the engine on. I have a whipple 525 dyno’d At 790 HP that’s going in. It already has a Bmax and I am curious if anyone has run an extension box. I have a stelling box sitting on the shelf and trying to decide if it’s worth the work putting it on. TIA

Can all depend on how far below the bottom of the boat your propshaft is currently. Moving the drive back further you'd typically want a higher x dimension.

I run an 8 inch extension box on my 07 Y2K. I have a little over 800 hp and have run 107 mph with a bravo XR and a sport master lower. I just did a little upgrade and I’m pretty sure she’s got 110 in her now but we gonna let a new owner find out. I think my days of pushing the limits are done.

Thank you for the advice. Do you think your box made a difference? I have a pair of stelling boxes and am considering using one it’s a question of if the juice is worth the squeeze. It is the older hull design from what I understand being an ‘05. Really trying to pull from y’all who have experimented already rather than reinvent the wheel. Thank y’all!

I ran a 525 with ITS, never had run my boat without an extension box. I like the way my boat handled as well as the clean installation of the ITS/steering Rams. I did run a higher x dimension when JC set it up at Superboat. My 2006 bottom was the same as yours not the current steps. Might consider an imco shortie if you go with the box.

I’ve got a two inch shortie on the B max now. Y’all think the stelling might be too much box? I’m really on the fence as to which way to go

On your current set up with the drive parallel to the bottom how far below the bottom is the prop shaft

I’ll have to measure I’m gone for Xmas right now. Where would you want it to be?

My boat was built with a Konrad package that had a transmission so the hole in the transom was about that of a number 6. I modified the box to a bravo transom. I wish I had the ITS. I’m -2 and have gone down and then came back up.

Occjoe. I read the thread on your boat. I’m jealous nice work! As far as mine goes am I to read between the lines and understand sell off my boxes and go get an ITS? Or go with “run what you brung” theory and slap the stelling on. The integrated steering arms while nice don’t close the deal for me. I don’t mind the the “current look” at all and unless I am missing something it would appear to me that the only real advantage of the ITS over other boxes is one of “ one stop shop, clean looks”