What all would take out a coupler?
 

I lost a coupler last year put new one in and less than 10 hours later took the new one out.

The drive appears to be fine, as it did last time. There was some metal flakes in the drive very small amount, nothing broke and the drive was not locked up. It would shift into fwd and rev just fine. There was a very slight drag when spinning the prop by hand in neutral. So I took it off and pulled it apart. This time I pulled the drive apart and again only found some damage to the brass part of the gears, the part where the shift for rides.

I am wondering if the drive is locking up and taking out the coupler or if I have two problems.

What should I be looking for that could take out a brand new coupler in under 10 hours.

FYI. I have not run the boat hard since I put the new coupler in. Max rpm has been around 4k, 65 mph. The boat has not been out of the water during any time the last 10 hours. Every time we were out the lake was flat.

Thanks
Rob

My guess would be alignment.

+1

bad alignment, bad motor mounts, bad transom/stringers letting things move

Alignment was perfect both times. The first time I had just replaced the motor so it was checked. The second time we replaced the coupler so we checked it again.

The boat has offshore mounts so it really can't move.

I will check this again, once I put the new coupler in.

Lack of lube on the coupler / input shaft splines or alignment problem which could be caused by many things.

Was it the metal spines that failed or the rubber???

Assuming the spines, a lack of grease will cause the coupler to fail.

If it is aligned and greased, then something is flexing. Either an engine mount or the transom.

[QUOTE=phragle;3158464]bad alignment, bad motor mounts, bad transom/stringers letting things move[/QUOTE

When you sa ybad transom what do you mean? Like a soft or wet transom? Or a bad inner transom plate for the drive?

I will check mounts and stringers at last survey all that was perfect. That was just a couple of years ago and the bildge is never left wet so I don't expect this will be the problem.

Is there something that could cause the drive to lock up for a second and take out the couple and then free up.

I have not pulled the couple yet. But I smelled rubber burning and saw smoke when it went, so I am assuming the rubber let go.

I'll get in there and look around for anything loose and will let you all know.

Thanks for all the ideas so far.

+1

Try standing on the outdrive, just above the prop, and jump on it some. Look for any flex in the transom.

Just looked back there now. The rubber actually exploded there are pieces everywhere. Same thing that happened last time. The spline still looks new from what I can see of it.

Stringers, motor mounts all very tight and in great shape.

I don't think there is a possibility of teh transom being soft at last survey moisture reading was 5 or 6%. The surveyor said it was one of the driest boats he ever checked. He said a brand new boat will hit 6 on his meter. The boat has only been in the water 30 times since then and only over night once.

The only thing I can't tell the condition of is the rubber and steel bushings that are installed in the bell housing. When I pry on that with a bar it is thight as can be. Those were replaced when I replaced teh motor 2 years ago.

Still searching....

OK, long shot, but I seem to recall reading something about HP couplers requiring somewhat of a different process over stock when putting the motors in. Wish I could remember the thread. That is the only thing I haven't seen mentioned already. Hope that helps, I'm out of suggestions.

Thanks for the info I will search around for thr post you are talking about.

I remember that too but I think it was something to do with the drive shaft bottoming out in certain couplers and pushing on the coupler, in turn stressing the main bearing.

But i could be wrong.

im having the exact same problem! i just blew the second coupler in 30 mins of boating! my motor mounts a offshore as well and the strigners are fine but we did find the top gears in the XR drive were worn and blue, my drive is currently being looked at by a mercury tech as it is still under warranty, my mechanic doesnt understand why this is happening either as alignment is perfect, every one is saying alignment and everything seems fine in my boat, we even tested the stringer by lifting on the motor while it was still bolted to the mounts and it pretty much lifted the boat off the trailer so its safe to say the stringers are fine! dont know whats going on either

the drive/input shaft have some runnout?? a little wobble would do the same thing as a bad alignment...

what do you mean by runout??

very slight bend in the shaft

Please keep me posted with your outcome. I'm pulling my hair out.

I will check this.

keep me posted as well cause nobody has an answer for me , i really dont feel like doing this a third time! what coupler part number did you install and on what drive and motor, mine is a XR on a 525efi. both times it happened to me i just finished passing a big cruisers wake but my mechanic swears everything is tight and nothing is moving, but my top gears are finished,need to be rebuit

Our problems are a little different as my gears still look brand new. If yours are blue that would be a sign of excessive heat. So i would guess there is something wrong inside your drive. From what I can tell most of my internals don't show any problems that would cause teh drive to lock up.

I will keep you posted though as to what I find out.

Mine is a 600SC connected to a XR drive.

Is this the post your talking about. This is what happen to me.
http://www.offshoreonly.com/forums/g...p-coupler.html

Yes

update? did you find the problem. I had my coupler explode and don't want a repeat.

Are you running the HP Couplers with steel splines and snout or the standard coupler with aluminum splines? If it's the rubber maybe you just got a bad coupler. Seem's odd to me, I'd have to see it in-person.

I blew a coupler once in my 36' and the only reason that happen is because I blew a drive and it locked up but that was before I got the BMax drives. Matter of fact, the coupler didn't actually blow, I ran it the following weekend and replaced it the weekend after that because the rubber was starting to fall out. I'm running the HP couplers with steel splines on 800+ hp..

Have you checked the gimbal rings for excessive wear/play?

Mine had the steel splines. The rubber is what exploded & took out the rear mount and wye pipe. Lucky it happened close to shore so we could paddle in before sinking.