gs 720 exhaust manifold studs broke off

[bobbo]

I just picked up a 2000 gs 720 with 2 of the 4 studs broke off on the upper part connecting to the pipe on the manifold.
1 what would cause this ?
2 are all 720 manifolds the same if I can't easy out them?

Any advice at all on this will be much appreciated

 

[bobbo]

Ok so when I posted this I found the answer to why they are breaking in a related that popped up so now I just need to know if all 720 manifolds are the same so I can find a used one

 

[Dr Honda]

Yes they were. The pipes are a little different though.

 

[bobbo]

Thank you I'm pretty confident I can get em out with an easy out but just in case I mess it up I don't want to spend $400+ on a new manifold

 

[parrothd]

check the drive line and rubber inserts on the muffler or you'll break those bolts again..

 

[bobbo]

check the drive line and rubber inserts on the muffler or you'll break those bolts again.. .... Ok I'm hoping it is the rubber inserts just .. But by driveline just make sure it is straight and no chunks out of the impeller?

 

[parrothd]

Yep, bad wear ring, bent drive shaft, bad prop, basically anything that can cause any excessive vibrations or excessive rpms...

 

[bobbo]

So I took the nozzle off and looked the impeller and it has 2 nicks outa it on each blade about the width of a pencil I'm guessing that is what is causing the bolts to snap off

 

[roneagan@cfl.rr.com]

One of the engines in my boat has done this, and there is nothing wrong with anything.. I drilled out the holes to 10mm, they were 8 and got a nylon lock nut for the stud which I left at 8mm.. I used allen stainless cap screws for the 10mm bolts.. I have gone through all the posting on this and it appears this is a fairly common problem on some engines.. I have 3 skis and the boat and this is only one that gives me any grief, It was fine until I removed it to weld up the leaking plugs in the pipe..