Is it a coupler or dog clutch?

[Rugby Lock]

Hello all,

I was bombing around on a local lake in my 19' 79 Cobalt OB with a mercruiser 260 this past week end when something happened. I was at WOT and everything was going great then the engine revved like when you put your car in neutral and give it some gas and I lost thrust. So, I put the boat in neutral and opened the engine compartment to check things out. I immediately noticed a burnt rubber but couldn't see anything else. Then I put it back in gear and everything engaged and I started to go again under low power but when I tried it again the same thing happened, engine revved with no thrust and burnt rubber smell. So, I killed the power and waited a minute. Then I put it in gear under low power and was able to make it back to the ramp. I have heard that this could be a spun prop, slipping dog clutch or an engine coupler. Based on what I have read here, but I am no boat mechanic, I am inclined to think it is the coupler... Hope I'm wrong but... LMK what you think it might be. Thanks for the help!

 

[thumpar]

Re: Is it a coupler or dog clutch?

Rubber is from the coupler. Pull the drive and take a peek.

 

[Rugby Lock]

Re: Is it a coupler or dog clutch?

Will I have to remove anything else? What am I looking for? Thanks for the help!

 

[thumpar]

Re: Is it a coupler or dog clutch?

The engine will have to come out to change it but you should be able to get a look at it with the drive off.

 

[stonyloam]

Re: Is it a coupler or dog clutch?

Symptoms say coupler.

 

[81 Checkmate]

Re: Is it a coupler or dog clutch?

Coupler.......

 

[HT32BSX115]

Re: Is it a coupler or dog clutch?

Will I have to remove anything else? What am I looking for? Thanks for the help!

Look back behind the engine with a mirror and a flashlight. You should be able to see powdered rubber back there if it's the rubber part of the coupler. That is not the only way a coupler fails though. The inner splines are aluminum and if they fail, it'll be like someone ran a drill through them.

Either way, the drive and the engine must be removed (in that order) to replace the coupler.

You'll need a service manual and an alignment tool along with some type of suitable lift.......

 

[Rugby Lock]

Re: Is it a coupler or dog clutch?

Pretty much what I figured... :Cry::Cry: JK
I am looking through the manuals online and I am having a tough time finding the section that cover changing the coupler. I found a section in manual three on removing the engine just can't find anything on the coupler. Also, since I will have to take out the engine what else is back there that I should change while it is out?

 

[HT32BSX115]

Re: Is it a coupler or dog clutch?

Pretty much what I figured... :Cry::Cry: JK
I am looking through the manuals online and I am having a tough time finding the section that cover changing the coupler. I found a section in manual three on removing the engine just can't find anything on the coupler. Also, since I will have to take out the engine what else is back there that I should change while it is out?

You need to carefully inspect your transom, and engine-mount stringers (since they may the reason your coupler failed)

Couplers fail because the engine alignment is NOT maintained.

This is why Mercury recommends check/adjusting the alignment every year. You shouldn't have to adjust every year but HAVING to adjust might alert you to problems such as the transom and engine mounts rotting (and MOVING ) which will usually result in coupler failure.

 

[stonyloam]

Re: Is it a coupler or dog clutch?

Remember you don't have to actually remove the engine from the boat, just pull the outdrive and lift the engine up and move it forward enough to access the flywheel cover and coupler bolts.

 

[Rugby Lock]

Re: Is it a coupler or dog clutch?

Thanks for the advice HT32 & Stony! Much appreciated. It is an old boat that was quite neglected before I bought it so I figure I should spend some time back there replacing any seals or parts that need to be taken care of. Aside from the transom and engine mounts (great suggestions btw) what else should be checked and what seals should be replaced? I noticed some extra water in the bilge so what could cause that?

 

[Bondo]

Re: Is it a coupler or dog clutch?

Thanks for the advice HT32 & Stony! Much appreciated. It is an old boat that was quite neglected before I bought it so I figure I should spend some time back there replacing any seals or parts that need to be taken care of. Aside from the transom and engine mounts (great suggestions btw) what else should be checked and what seals should be replaced? I noticed some extra water in the bilge so what could cause that?

Ayuh,.... Welcome Aboard,.... Unfortunately, the most likely culprit is a Rotten Transom,...

 

[Rugby Lock]

Re: Is it a coupler or dog clutch?

Well that's not good news... is this a difficult and expensive repair?

 

[HT32BSX115]

Re: Is it a coupler or dog clutch?

Well that's not good news... is this a difficult and expensive repair?

It's generally a "NOT-WORTH-IT" repair.

If that's the case, your best bet will be to part it out (the engine and drive, etc) cut up the boat and send it to the dump, and use the money you get from the parts to find yourself another boat.

Sorry about that.....

 

[stonyloam]

Re: Is it a coupler or dog clutch?

Drop in over at the boat restoration discussion group and they can tell you how to check your transom and give you information on repairing it if it is bad.

 

[Rugby Lock]

Re: Is it a coupler or dog clutch?

Well, I confirmed it was a bad coupler when I stuck my hand back there and felt a bunch of rubber shavings on the coupler... As for the transom I did the tap and listen test and found a few small areas with the dreaded hollowish sound but the majority sounded good. I will do a more thorough inspection when I get the engine out and the transom plate off. What seals and stuff should I look at replacing since I have everything off if it turns out the transom is not in the "not worth it" category?

 

[Rugby Lock]

Re: Is it a coupler or dog clutch?

bumpity bump bump bump!

 

[Bondo]

Re: Is it a coupler or dog clutch?

bumpity bump bump bump!

Ayuh,.... At this point, IF the transom ain't rotten, you only need the $6. gasket set to put the drive back on,...

You should do some browsin' through the Restoration forum, the Dry Dock,...

The Odds are, a rotten transom Caused the coupler failure,...

 

[Rugby Lock]

Re: Is it a coupler or dog clutch?

Not so sure the misalignment was due to a rotten transom. There are some hollow areas but the bulk sounds good (of course when I get the engine out this week I will be able to examine it better) but I think I found the culprit. Being a total newb to boats i never really thought about it but when y'all starting mentioning alignment a light went off in my heat (incandescent not cfl...) when I was examining what I needed to detach to remove the engine. The front starboard motor mount was not secured... The bottom nut is all the way down and the top nut and lock washer were not tightened down so I am thinking the engine did some bouncing while bombing around at 40+mph and that caused undue stress on the coupler thereby causing the failure. What do you think? I will be pulling the engine this week and hopefully be reinstalling it in two weeks. Fingers crossed that all goes well!!

 

[Bt Doctur]

Re: Is it a coupler or dog clutch?

A loose front mount will take out a coupler too