Drive coupler question. 86 merc 4 cyl. I/O

[Seasonally.boating.jon]

I was told, if the coupler goes bad, then more than likely the lower unit is bad. The coupler will go bad to save the engine. I was just wondering if this could be true.

The lower unit is off. Spun the shaft by hand and it seems perfectly fine. Coupler is shot for sure. The motor was running fine before removing the lower unit, it just made a awful sound as the shaft was spinning. If you need more info on the motor just let me know. Thank you.

 

[Ciera22]

Re: Drive coupler question. 86 merc 4 cyl. I/O

Hope someone answers this my buddies I/O unit started making this clattering noise tonight and I'm wondering if it this coupler you mention?

 

[Don S]

Re: Drive coupler question. 86 merc 4 cyl. I/O

I was told, if the coupler goes bad, then more than likely the lower unit is bad. The coupler will go bad to save the engine. I was just wondering if this could be true.

No......

The reason couplers go bad is because the alignment is off or lack of lubrication. Of course, if an outdrive locks up, it may very well take out the coupler, but the coupler is not going to protect the drive.

 

[Seasonally.boating.jon]

Re: Drive coupler question. 86 merc 4 cyl. I/O

Very helpful. Thank you for the picture. Looks like we have an alignment problem.

 

[series60]

Re: Drive coupler question. 86 merc 4 cyl. I/O

I was told, if the coupler goes bad, then more than likely the lower unit is bad. The coupler will go bad to save the engine. I was just wondering if this could be true.

The lower unit is off. Spun the shaft by hand and it seems perfectly fine. Coupler is shot for sure. The motor was running fine before removing the lower unit, it just made a awful sound as the shaft was spinning. If you need more info on the motor just let me know. Thank you.

First thing is stop listening to the person that told you:

if the coupler goes bad, then more than likely the lower unit is bad.

The noise you heard was probably the drive shaft splines destroying the coupler splines.

The motor was running fine before removing the lower unit, it just made a awful sound as the shaft was spinning.

Engine alignment is CRITICAL to coupler longevity! If the coupler goes while WOT you may ream the engine if you aren't quick on reducing power but it is not intended to save the engine and is not indicative of a bad outdrive. It is there to connect the engine to the outdrive through the use of a rubber/metal spline combination. YEARLY removal of the outdrive is a must if you want the coupler to have a long life. With the outdrive removed you can now inspect the gimble bearing, lube the shaft splines and most important check engine alignment.

You are dealing with a 26 year old boat which, if my guess is correct, the engine mounts and transom have given some from their original position. You may have rotten wood in the transom and or engine mounts or stringers or all of the above. ANY mis-alignment of the engine will shorten the life of the coupler!

 

[River's Revenge]

Re: Drive coupler question. 86 merc 4 cyl. I/O

This is all oh so true Series... many people don't see it for what it is. a motor aligned with a propulsion shaft. So when you do your alignment. use the rule of thumb, if the tool goes in and out with the use of two fingers and checked at least 180 or 90 degrees again. well then you should be good.

 

[Seasonally.boating.jon]

Re: Drive coupler question. 86 merc 4 cyl. I/O

I like your theory about the rotten wood, series. I would bet the farm that the mounts, trans, and all are rotten. This is a older gentleman that has the boat. I'm 32 and gave my thoughts about it. Ofcourse he is much more wise than I.

Wile the motor was running, the mounts vibrated alittle but they did not move. Thats what I was looking for, movement at the mounts. To remove the coupler, we unbolted the engine. I noticed A lag bolt was on the dark wet side. But anyway, the splines are perfectly fine. As for the rubber inside, ground up pretty good. The sound the coupler made wile running kind of resembled bad hub bearings running about 55mph down the highway. I wish Took pics of the inner hole so ya'll could see.
Thanks alot.