XR upper top plate
 

Pushed the top plate off my xr upper , pushed the front 2 bolts out . Is this a common thing for these drives ???? :mad:

Are you talking about the top cap that is held on by four bolts ?? If so I am gonna guess that you have a twin engine set-up and this is the port side drive?? If so the twisting force is transmitted upward when in forward gear.

To fix it drill it out and helicoil the case and replace the bolts with studs. Then torque and check frequently as they will loosen over time from the upward torque.

Smitty

Yes it is the top cap but it is on the starbourd side. thanks for thereply jeff :mad:

I changed mine to 7/16 studs and billet top cap,Smitty

Jeff,
the drive that has the LH prop on it, uses the top gear for fwd. There is a lot of presure on the top cap. The cap is a very weak piece and should be replaced with a better top cap. I use the Merc XR top cap and a stud kit. It has a steel tower in it and is a very strong piece. So I would helicoil the holes and use studs with a good top cap. If you replace the top cap you have to measure the depth of the race on both caps and change the shim accordingly.
Did your top cap come completely off or just pushed up.. either way you better check for damage to other components in the upper gear set and bearings..

Hope this helps.
Dick

Looks like i will put 7/16 studs in them and try that , thanks again for the help Jeff :ernaehrung004:

When you drill it for 7/16" the case gets real thin. I recommend the heli coil and studs. Cause once you go to 7/16" you cant go back..
just my .02

xr topcaps
 

We use a 1/4" longer, grade 8 stainless cap screw for our billet water cooled topcaps. We do offer a 7/16" for already drilled cases but do not recommend the modification...
Curtis @ www.billetmarine.com

Curtis, I was just going to ask if anyone here was running your billit top cap? I was looking at your site, and it looks like a very strong part. Does a standard drive shower line/ fitting screw into your top cap?




Darrell.

Max Machine Worx makes a nice piece http://www.maxmachineworx.com/upperTopCap.htm

After looking at it this weekend I found 1 tooth broke on a gear . I'm thinking when the tooth went through the gears it pushed the top cap up and pulled the threads. As you have said there is not much meat there so I will go with the heli coil's and stud's. Still not sure why it broke ? The drive has less than 50 hours on it. Thinking about going back to bravo 1's if I'm going to be braking drives it might as well be the cheap ones. Thanks again for your advise, Jeff :ernaehrung004:

Jeff,
I have seen more of this problem than I want to. XR upper gear sets, one tooth broken off at the root of the gear. Happening more and more. Used to be we could run 1100hp thru the gears and they would just flake away. Now a perfectly good gear just snaps a tooth off.
My .02 is that Merc has another supplier and quality is not an issue. If people want to run big power (over 550hp) then just opt for the new NXT / 525hp package. Of course you will need to order the new boat with that package also..
I have been talking to someone that says he can make better gears, just dont have the $250k to try a set.
How much HP and Torque? How much does the boat weigh? You may be right. The Helical cut gears may be better at this point. I have always said that if you dont have enough power to knock the teeth off the Helical's, then run them. You still have the problem of the lower gears falling apart.
My sugestion is go with the IMCO SCX. It has bigger gears and no problems so far. But the lower unit is larger, and it will slow down the boat. So add more power if you can (add boost?) or be ready to replace the weak link often..

Dick

The motors dyno'd at 742 hp and 830 ft-lbs and I'm turning 31 pitch 4 blade merc prop's . The boat ran for 200 hours on bravo 1's when it started to twist the prop shaft's . So the xr's were put on with imco lowers and now this sh!t . At least I have all winter to fix it . :ernaehrung004:

Jeff,
You might want to think about going back to the helical cut gears in the upper.. the XZ gears will fit your XR upper case, properly setup. They are the weaker setup, but with the XR gears wearing out and falling apart, in your case the XZ gears may suit your maintenance schedule expectations. I know a lot of guys that think along these lines and their drives hold up pretty good. They know they are breakable, so driven with caution they seem to last. Not forever, but acceptable time frames for their expectations.
Dick

Looks like I'm going to fix what I have . Just burns my but when you spend the money on the so called good parts and this happens. Thanks again for the advice . Jeff :ernaehrung004: