What causes a Boat Engine Coupler to fail on startup?

Question

Hello boating community,

I recently took out my boat(glasstron) for a spin and was towing someone on a tube. To note it was a little harder to get it up on a plane than expected that day. When we stopped and turned off the engine, we loaded someone on the tube and tried to start the engine. It turned over and revved but did not drive in any direction. This is a boat that needs the use of throttling to start the engine (maybe I throttled too much??).
It was taken into the mechanic and the diagnosis came back that the boat had a failed engine coupler. How could this have happened? and is this just a part that needs to be replaced on a boat occasionally or could it have been something we did in starting the boat?

I am very grateful for anyone that could help me understand what could have gone wrong and enlighten me on how often engine couplers should be replaced on a boat. Thank you!

Answer 1

It sounds like you might have an "older boat" (Glastron) with a Mercruiser Stern drive. The lower unit splined shaft mates to the engine through a "Coupler". It's bolted to the engine flywheel. the Female splined coupler is mounted to the coupler by a rubber hub, very similar to how the propeller is mounted at the prop shaft.



They fail because the rubber gets hard over time, but mostly from running aground. Often in muddy or sandy bottoms. They also don't last if you use the stern drive in a partly tilted position, like if you've ventured close to shore and raised it to prevent damage to the prop.



When it's old enough the strain of pulling tubs can weaken it. Unlike the prop which only turns when in gear, the coupler turns all the time, and if you raise or lower the drive it has to accommodate any misalignment between the engine and drive.



The stern drive is removed, then the engine has to come out to replace the coupler. And the part is a couple hundred. I think the time should be about 4 to 5 hours to do the repair, and the engine must be aligned after the coupler is in stalled.

Answer 2

Good enough a number of folks almost received it right.But they are only close. The coupler is the part that's bolted onto the fly wheel. The splined enter shaft from the out power slides into it. If the splines appear just right on the shaft the splines within the coupler may be worn out. This occurs due to the fact that men and women don't hold there boats accurately. It is also a wearing section and can finally fail. Also what will occur is the rubber hub on the coupler will quit the ghost and it is going to spin. It is regularly rough to see the splines , the quality technique to assess this is to insert a enter shaft into it and switch it. If it turns and the engine doesn't the coupler is trashed. The object is this isn't an costly part.You can get them just about any have been.

Answer 3

Engine Coupler

Answer 4

One of the main reasons the engine coupler ( drive doughnut ) fails is poor engine alignment.

When ever the stern leg is removed for regular servicing, an alignment tool should be pushed up through the gimbal bearing and into the coupler.

The tool should slide easily into the coupler without having to use force.

This should be done with the flywheel at 90 deg intervals, a total of one complete revolution.

this will determine if the coupler is distorted or if the front engine mounts are out of alignment.

If there is poor alignment and the coupler is trying to work through an angle, the rubber in the coupler will heat up while under load and eventually let go.

Answer 5

You have to look at what holds a coupler, usually 4 bolts and the compression from them and a key. What likely happened is you spun a key, broke the key, and the result was the coupler spinning around the shaft. Does happen, not often.

Answer 6

you spun a baring some whare is the shaft to the prop 1 peace? it could be the prop bering or eng bering do not run til u know