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.