Need help with drive height!!!
 

I just got my boat back from getting the engine checked. They told me that my drive was too deep. So here is the spec. for the boat. 28’ deep V single step, single engine 565 quad 1,000 hp with a B1 max’s drive, no stand off box. From the center of the prop shaft to the bottom of the V is 3 ¾” (below). They said that it needs to be at the same as the bottom? What is correct? I have a standard Imco lower with a 1” spacer now.


Thanks for your help!! :rolleyes:

Re: Need help with drive height!!!
 

I would start by testing without the spacer. One inch can make a lot of difference.

What specific boat/model?????

Re: Need help with drive height!!!
 

Caliber1 280 offshore thunder had 1" off already but it didn't help. What is your at? I'm asking to see if that is why I break drives?

Re: Need help with drive height!!!
 

I think 1000hp on a bravo style outdrive is why you break drives.

Re: Need help with drive height!!!
 

Yes but I don't run it at full power it's at 900hp right now. I have a 32 lab prop which is at alot of slip right now. BTW no room for a #6 and the Konrad 540 is $28k, just need the height. :(

Re: Need help with drive height!!!
 

IF you are breaking drives its not surprising, you are up to high now! you need to space down further. or install a ext. box.

Re: Need help with drive height!!!
 

My PSH is at 4.25" below the bottom on my 28 Pantera. I agree, NO Bravo style drive is going to last behind 900-1000hp.

Re: Need help with drive height!!!
 

I'm a little confused on the drive height thing.Not trying to hijack your thread just like some info to.Matt at throotle up wants me try try a 2" spacer and manufactor says try a 2" shortie.Matt has been right before with me.I'm about 5" below bottom of boat.10,000lbs,twin whippled 525's and about 17% slip with labbed 32's.trying stock 32's and labbed 34's.Thanks inadvance.

Re: Need help with drive height!!!
 

Based on your information your drive is at a good height, if anything it is a little high. Does your boat have a notch? If you had an extension box and a long notch maybe, just maybe, would you want the prop shaft even with the bottom of the boat.

What are your performance numbers; speed, rpm and gear ratio? How does the boat get on plane? When at max speed, properly trimmed, does the boat shoot a rooster tail?

Matt

Re: Need help with drive height!!!
 

Thanks to all of you!! I had Gary at GT Performance tell me my drive is ok at the height it's at! As far as the drive I have had great luck with the Maxs drive, just the OEM XR gears that are not working, the boys at Maxs have their gears being made right now and will have a set in a few weeks. Some of the new XR gears coming out right now are not hard-ed like the older ones. BTW never broke shafts just gears!!


Thanks for alll the great info. on this site!!!! :drink: heres to summer!!!

Re: Need help with drive height!!!
 

565, how close is your step to the transom of the boat ? If your prop is running in aerated water which it sounds like it is, that might be the problem, and not the drive height as you are running high right now for a non race v hull. The higher you go with your x dimension your handling will suffer even in a straight line. I would try your existing set-up with either more blades on the prop- (maximus ?) to deal with the aerated water- or get the 2" spacer to get your existing prop to hook up- in cleaner (deeper) water.If you do decide on a standoff box- I would get a Stellings as you can fine tune the X dimension but I would say a neutral- 0 rise may benefit you with a single high hp 28' , again just cleaner water. I know it can be a pain but I have even resorted to hanging off the back of the boat to watch how thewater and how the drive is running to determine a fix, understand your weight all the way back there will affect the boats normal attitude. Or ride in a friends alongside, even video how your hull rides at the drives contact point with the water at different speeds and water conditions. If it's white, your in "dirty" water. On the subject of the oem xr gears, they seem to last around 60-70 hrs and then frag. As good as they seem to be designed with the larger square teeth and "backing" support under those teeth, the contact area is not as great as the "old" beveled gears. Mercury should go back to the drawing board on these to make them stronger, I would assume the "backing" of the gear teeth alone would make a huge difference to the old gears. "New" gentlemen, is not always better. What do I know though, I'm running 642h.p. w/ Blackhawk in a " true" air entrapment tunnel, with the old beveled gears. Good luck - Viol8or