Engine Coupler Problem?

[myoldboat2]

Hello -

I have a 1970's Mercruiser 140 hp with a Mercruiser I (or maybe I-R) outdrive. After starting for the frist time since winterization last fall, the drive wouldn't shift into forward or reverse, there was a thumping noise from the rear of the engine, and the engine temp started climbing. I was able to determine that nothing in the outdrive was turning. By watching the splined shaft that connects the outdrive U-joint to the engine coupler, I could see that it was basically not turning--just erratic movement, maybe turning 3/4 turn in 30 seconds. I removed the outdrive. The U-joint and splined shaft look OK. The outdrive seems to work fine in forward and reverse when I turn the U-joint by hand. When I run the engine with the outdrive off, it runs great, and there is no longer any thumping noise.

Do you think the engine coupler has failed? Or could it be something else, as scary as the end of the crankshaft breaking? Do I need to pull the engine to even be able to inspect the coupler?

Also, does it look like the splined shaft was inserted far enough into the coupler? Some of the splines were showing. I have read that the wrong combination of drive/bellhousing/transom can result in not enough spline engagement, but I'm not sure how far it should engage.

Thanks in advance for any advice you can offer.

 

[myoldboat2]

Re: Engine Coupler Problem?

Here are the rest of the photos.

 

[Reel Poor]

Re: Engine Coupler Problem?

I believe you have a pretty good handle on your problem. From your description it sounds to me like the coupler has failed. Yes the engine will have to be remove for service. You may be able to remove the gimble bearing and seal and get a slightly better view of the coupler. If it's bad you will notice distorted and burnt/melted rubber. The spline engagement depth look good.

 

[myoldboat2]

Re: Engine Coupler Problem?

Thanks for the reply, Reel Poor. I am getting ready to pull the engine. That will be an interesting project. On the spline engagement depth, my understanding as of now is that the rear engine mounts set the left-right alignment (not really adjustable), and the front engine mounts allow adjusting the up-down engine alignment (using the alignment tool). So I wouldn't have any idea how to adjust the fore-aft engagement depth of the driveshaft splines, unless there had been a wrong part involved. So I am relieved that you think the engagement depth looks good--thanks for that info.

 

[Reel Poor]

Re: Engine Coupler Problem?

BTW, nice idea on the kicker bracket.

 

[Coors]

Re: Engine Coupler Problem?

Yeah, I was eyeballing that bracket, but my swim platform nixed that one.