Transmission/driveline/coupler failure? Boat don't go!

Moving this discussion over from where I mistakenly posted it in the Mercury Outboards forum... Consensus so far appears to be that it could be an issue with the coupler.

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Today on the lake something failed in the driveline. I didn't hear any kind of a clunk or other noise, but the engine immediately raced in RPM and I shut it down. Afterwards, when I shift into gear, the boat don't go anymore. It's also not pumping cooling water anymore; Fortunately I managed to limp it back on a trolling motor (a 4 hour trip, but better than spending the night on the lake).

I checked the shifter cables and they look fine so far as I can tell. Shifting into gear and manually spinning the prop from the outside, I am able to feel some resistance, but it's certainly not connected to the motor.

I have a service manual somewhere that I'll dig out, but I was wondering if anyone had an idea of the most likely cause? It's a 1993 Bayliner, 4.3 liter, Mercruiser motor and stern drive.

Thanks,
Scott

Re: Transmission/driveline/coupler failure? Boat don't go!

Cause is likely lack of maintenance, water ingestion in the drive and/or lube. Not always, but usually a drive coupler replacement requires that the engine be pulled from the boat to replace it.

Re: Transmission/driveline/coupler failure? Boat don't go!

Slip Away said:

Cause is likely lack of maintenance, water ingestion in the drive and/or lube. Not always, but usually a drive coupler replacement requires that the engine be pulled from the boat to replace it.

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Howdy,


Welcome aboard!!


You most likely have a coupler failure.

It's not related in any way to water injestion or lube (except coupler lube)

The lack of maintenance would be not removing the drive and checking the alignment.

Also, if you have water intrusion into either the transom OR the engine mount stringers, they become soft and the engine and/or drive loses alignment.

Coupler replacement ALWAYS requires the engine to be removed to replace it (otherwise you cannot check and adjust the alignment.....which is usually the cause of coupler failure)

Plan on removing the drive AND engine as a minimum to replace the coupler.

Then carefully inspect the transom AND engine mounts for ROT and water intrusion etc.

If the transom is rotten (and the stringers) it may not be worth it to fix if you cannot do it yourself........in that event, you might start looking for another (good) boat with a cracked block etc..... (wait until Spring when they start "springing" up!!)


Sorry about that!


Rick

Re: Transmission/driveline/coupler failure? Boat don't go!

If It happened that abruptly without and sudden noise or burning smell, the failure might be in the drive.
Could be the vertical driveshaft.......wouldn't be pumping water if it's broken.

I would remove the drive, put in in gear and turn the driveshaft by hand (clockwise), if the prop don't spin......it is in the drive.....

Re: Transmission/driveline/coupler failure? Boat don't go!

FreeBeeTony said:

If It happened that abruptly without and sudden noise or burning smell, the failure might be in the drive.

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Absolutely right. When mine failed it didn't make much noise and there was no rubber. It did look like someone drilled out the coupler though.........All the inner (aluminum) splines were gone!

Once the drive is off, you can use a flashlight and look through the gimbal bearing or use a mirror and a flashlight inside possibly.

With the drive off you can also turn the input shaft and see if it shifts normally before you pull the engine etc........

Hope it's just the coupler! If not, you may be looking at a drive rebuild/replacement, which will cost considerably more....

Re: Transmission/driveline/coupler failure? Boat don't go!

Bubba1235 said:

It's easy to pull the drive off. Once done you can dertermine if its in the drive or if its the coupler. You WILL need an alignment tool to re-install the drive.

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Ayuh,... 6 nuts, 'n a couple of clips are all it takes...
'n a $7.00 gasket set to put it back on..
It weighs 'bout 80lbs, so be ready when it slides off...

Pull the drive, 'n manually shift it into each gear...

See what's broken, insteada Guessin'...

Re: Transmission/driveline/coupler failure? Boat don't go!

if you can see between the engine and the transom, you will see there is the shaft going into the engine. see if that is spinning and see if the coupler there is also spinning. if couple isn't spinning then its your coupler that needs to be replaced. i had this problem last yr and that's a good way to tell.