Not a great day,,,,,,

[akwalker]

1987 OMC Cobra, 5.0 ltr. GMC, 1987 2150 Bayliner


Went out on the boat today. We were at wake speed comming into a marina for lunch, when all of the sudden there is a metallic grinding noise, and loss of forward motion. Shut down and coast into the dock. Got a ride back to our marina, fetched the trailer and loaded the boat.

Here is what I found. With the engine in forward gear, I am able to spin the prop shaft fairly easily, and can hear a metal on metal "bumping" comming from the upper (horizontal) driveshaft. So, I pull the outdrive. The splines on the yoke shaft are pretty beat up, but not completely gone. My question:
What are the symptoms of a failed motor coupler? There was no warning of the failure other than the grinding sound at the point of failure. I'm hoping that it is just the yoke shaft, and not the coupler. Any comments surely welcome.

Also, would anyone know what the diameter across the splines should be on the yoke shaft? Thanks.
__________________

 

[akwalker]

Re: Not a great day,,,,,,

One other thing, while I'm thinking of it, towards the end of last season, almost every time I would put the boat in gear and start off, there would be a solid bang, sort of like a mild backfire. Please note, that the outdrive was fully engaging in forward gear, so I know its not in the gearcase. Is it possible that the shaft was failing and the male splines were slipping in the female? Coupler?

 

[boatguya1]

Re: Not a great day,,,,,,

If we're talking about the boat in your sig line then the ID splines on the coupler are made of aluminum and most likely damaged if I understand you correctly. Take a flash light and look up through the gimbal brg at the coupler. You shpould be able to see it and it's splines. With a steel shaft and aluminum splines they usually give out dirst.

James

 

[akwalker]

Re: Not a great day,,,,,,

 

[boatguya1]

Re: Not a great day,,,,,,

Sometimes the shaft splines appear to be wiped out but are really just full of aluminum from the coupler.

James

 

[boatguya1]

Re: Not a great day,,,,,,

Those splines don't look to be stoping you from moving based on what I see in the picture. If you shift the drive into gear and turn the shaft while holding the prop can you turn the shaft without the prop turning? Like I said you can see the coupler splines through the gimbal brg if they look good I think your problem is elsewhere.

James

 

[boatguya1]

Re: Not a great day,,,,,,

Sometimes the shaft splines appear to be wiped out but are really just full of aluminum from the coupler.

James

Typed that prior to seeing the pictures

 

[akwalker]

Re: Not a great day,,,,,,

Those splines don't look to be stoping you from moving based on what I see in the picture. If you shift the drive into gear and turn the shaft while holding the prop can you turn the shaft without the prop turning? Like I said you can see the coupler splines through the gimbal brg if they look good I think your problem is elsewhere.

James

The gearcase behaves normally. In other words, its not a spun prop or a problem in the gearcase. When I looked in the coupler with the outdrive off, I can see the female splines in the couple. Question:
Does the motor have to come out to change the coupler? As I stated in the first post, this is a 5.0 GM with a cobra outdrive. Thanks for all the input thus far.

 

[boatguya1]

Re: Not a great day,,,,,,

Yes engine must come out to change the coupler. I've generally not heard a metalic grinding noise on most coupler failures. I've had more than one customer tell me the rubber hub melting smelled like macaroni and cheese though. Maybe the coupler failed where it's attached to the flywheel, that would account for metalic grinding noise. If the drive is happy look's likke time to pull the motor. One more thing, is it possible the hub in the prop failed allowing the prop to **** to the side and contact the gearcase making the noise you heard. That's the only other thing I can think of if the drive is good besides the engine coupler flywheel area.

James

 

[danond]

Re: Not a great day,,,,,,

Luckily removing a boat engine doesn't require much drama. Much easier than a car.

 

[akwalker]

Re: Not a great day,,,,,,

Yes engine must come out to change the coupler. I've generally not heard a metalic grinding noise on most coupler failures. I've had more than one customer tell me the rubber hub melting smelled like macaroni and cheese though. Maybe the coupler failed where it's attached to the flywheel, that would account for metalic grinding noise. If the drive is happy look's likke time to pull the motor. One more thing, is it possible the hub in the prop failed allowing the prop to **** to the side and contact the gearcase making the noise you heard. That's the only other thing I can think of if the drive is good besides the engine coupler flywheel area.

James

Nice thought, but like I said, before I pulled the outdrive, I put it in gear and could turn the prop with very little effort, and I could feel and hear what seem like the splines slipping. I was not aware that the coupler splines were made of anything other than steel. I was aware of a burning rubber smell when the coupler fails, but we DID NOT experience this. Still going to pick up a new yoke shaft because the splies are worn almost to a point. In other words, very sharp.

 

[HT32BSX115]

Re: Not a great day,,,,,,

Nice thought, but like I said, before I pulled the outdrive, I put it in gear and could turn the prop with very little effort, and I could feel and hear what seem like the splines slipping. I was not aware that the coupler splines were made of anything other than steel. I was aware of a burning rubber smell when the coupler fails, but we DID NOT experience this. Still going to pick up a new yoke shaft because the splies are worn almost to a point. In other words, very sharp.

It's quite normal for there to be a clicking, ratcheting feeling when you turn the prop in the forward direction when it's in forward gear. the dog clutch in the Cobras works that way.

If you had spun a coupler (and it wasn't the rubber part but the inner aluminum splines) you would not be able to run in either forward or reverse.

There would be a LOT of aluminum on the yoke, and when you can see the coupler it would appear like someone drilled out the splines. (actually it's the yoke that "reams" out the inner splines)

if the yoke splines are worn to a point. it's probably because previous owners have NEVER lubed them or did it so infrequently as to cause the wear. (I had a 66 model boat that the coupler and splines went until 2005....actually I replaced the coupler and kept running it on the original yoke.)

If the yoke is worn as you say, the coupler should also be replaced. (you gotta pull the engine)

If you have shift problems, you probably need to replace the lower shift cable. If you don't have a correct year OEM service manual, now would be a good time to get one.


Regards,


Rick

 

[akwalker]

Re: Not a great day,,,,,,

It's quite normal for there to be a clicking, ratcheting feeling when you turn the prop in the forward direction when it's in forward gear. the dog clutch in the Cobras works that way.

If you had spun a coupler (and it wasn't the rubber part but the inner aluminum splines) you would not be able to run in either forward or reverse.

There would be a LOT of aluminum on the yoke, and when you can see the coupler it would appear like someone drilled out the splines. (actually it's the yoke that "reams" out the inner splines)

if the yoke splines are worn to a point. it's probably because previous owners have NEVER lubed them or did it so infrequently as to cause the wear. (I had a 66 model boat that the coupler and splines went until 2005....actually I replaced the coupler and kept running it on the original yoke.)

If the yoke is worn as you say, the coupler should also be replaced. (you gotta pull the engine)

If you have shift problems, you probably need to replace the lower shift cable. If you don't have a correct year OEM service manual, now would be a good time to get one.


Regards,


Rick

Thanks, Rick for the response. This was not the normal ratcheting sound caused by the clutch dog. Like I said, I could hear what sounded like the splines slipping past each other from the upper gearcase. Whats got me is that there was hardly, if any aluminuim in the splies of the yoke shaft. You are correct, I can't attest to how the previous owner maintaned the engine in the past, but that yoke shaft was just about vacant of grease when I pulled the drive.

 

[boatguya1]

Re: Not a great day,,,,,,

Maybe the whole engine coupler is broke loose. You might try sticking a long screw driver up there to see if you move it. I agree if splines on shaft are worn to a point you need to change the coupler also. As mentioned pulling the motor isn't a big deal especially if there's not alot of boat in the way.

James

 

[HT32BSX115]

Re: Not a great day,,,,,,

Thanks, Rick for the response. This was not the normal ratcheting sound caused by the clutch dog. Like I said, I could hear what sounded like the splines slipping past each other from the upper gearcase. Whats got me is that there was hardly, if any aluminuim in the splies of the yoke shaft. You are correct, I can't attest to how the previous owner maintaned the engine in the past, but that yoke shaft was just about vacant of grease when I pulled the drive.

Well,

if that's the case, you'll have to closely inspect the coupler (and if true, replace it)


I had the same problem with a nearly 40 year old Mercruiser.......Now that I remember it....I don't recall a lot of aluminum on the yoke.

It DID spin the yoke/coupler ....Slowly got to the point where it would go but it would "slip" once in a while during acceleration... of course it got progressively worse (quickly)

When it finally failed it would just spin in either FWD or reverse.

the yoke was usable.....a rubber coupler failure is of course, more dramatic what with the burning rubber smell and rubber dust etc.....


There is another failure mode. I had a guy describe a failure where the coupler (metal part) literally "exploded"........It took out the bell housing, transom plate, gimbal mount etc....

That was on a 460 King Cobra in a 28' Bayliner running at nearly full throttle.





The failure of the rubber "snubbe

 

[akwalker]

Re: Not a great day,,,,,,

Well, turns out that the coupler has failed. I removed the yoke shaft from the outdrive, and stuck it into the transom assembly. Shoved it all the way in, and I am able to turn it by hand. When I pulled it out, there was all the grease and aluminuim debris that others had mentioned. I think when I was looking in the hole with a flashlight, I actually was seeing the grease, not the splines. I guess I'll be pulling the motor as soon as I find a coupler. Thanks again to all that replied.

 

[Lou C]

Re: Not a great day,,,,,,

It seemed odd that the yoke didn't have any grease on it in the pic, did you clean it off to check the splines?...But you did say that there was grease in the coupler...I wonder if the alignment was off, or it wasn't greased each year...at any rate if it's the OE coupler it lasted over 20 years so I guess that's how you have to look at it....
I have pulled the drive each season and greased the splines with OMC/Bombardier triple guard grease, and when I pull it off at the end of the next season, the yoke splines are pretty much still well greased...
After you replace the coupler, make sure to get an alignment tool and check the alignment and the new one will last you as long as you have the boat....as long as your engine mounts are good and solid.....

 

[akwalker]

Re: Not a great day,,,,,,

Yep, will do. Nope, the splines came out fairly devoid of grease. PO probably used the wrong kind, I'm guessing. Anyway, it'll be nice to know theres a new coupler and shaft in there.