Mercruiser couplers...3 in a year!!!

[goblenick]

I have an "89 Sea Ray with a 4.3 Alpha One (gen 1) drive. Yesterday my engine coupler gave way for the third time in just over a year! The first one gave way in the late spring of last season. We had it replaced along with the bellows and gimbal bearing at a local shop ($1500 total). The mechanic explained an engine mount had come loose and misaligned causing the coupler to blow. About 20 hours of running later, the new one blew. I took it back to the same mechanic and he had Sierra pay for the new part and pay for the labot his shop performed (mechanic explained part had broken abnormaly). By the time I got the boat back, it was too late in the year to take it out. After putting around 25 hours on it this year, its gone again. Here are my questions:

1. What could be causing this repeated problem to happen? Could the shaft not be seating into the coupler as deep as it should? Could the shaft be out of balance causing it to wear out?
2. Has Sierra couplers given anyone else trouble?
3. Will a part number for one of the 5.7 couplers work in its place? If the part numbers are even different. I would assumbe the ones for a 5.7 would be built to handle more torque and both motors have the same drive and rear of the engines are the same to my knowledge.
4. Is this job incredibly hard to do yourself? I have a little mechanic experience and have a couple of friends to help that are more experienced than me.

Any help is GREATLY appreciated.

 

[Boomyal]

Re: Mercruiser couplers...3 in a year!!!

Recommend that you check the alignment yourself. Misalignment is really the only reason that a coupler would go out. Along with the alignment, I would check for transom and mount stringer integrity. If any of those two items are compromised, then it is possible that the alignment is good at rest but when the engine is running the torque moves everything out of alignment. I don't quite understand the claim that 'the engine mount had come loose'. What does that mean exactly?

Sierra makes a lot of boat parts and I doubt that you would get a string of bad ones

 

[goblenick]

Re: Mercruiser couplers...3 in a year!!!

Thanks for the advice. As far as the engine mount, the way he explained it the engine mount (bolts) had worked themself loose and misaligned the engine.

 

[Limited-Time]

Re: Mercruiser couplers...3 in a year!!!

Thanks for the advice. As far as the engine mount, the way he explained it the engine mount (bolts) had worked themself loose and misaligned the engine.

Engine mount to engine, or engine mount to stringer?? Neither are common, but if its the engine mount to stringer you need to take a good close look at your stringers.

 

[Don S]

Re: Mercruiser couplers...3 in a year!!!

The rear motor mounts are probably bad. They get soft or seperate and allow too much engine movement. I have always recommended changing the rear mounts any time a coupler fails. It's also possible the mounting hardware is not installed properly.

 

[goblenick]

Re: Mercruiser couplers...3 in a year!!!

Both of these soud like very possible reasons. I don't know if the marina that replaced the coupler last year bothered to check the engine mounts/stringers. I'm going to attempt to do it myself soon and I'll check them. How difficult is this going to be to do? I can have the outdrive off in under an hour and I've pulled engines from cars before, but I don't know how difficult its going to be to pull the bellows, etc. loose to get the engine out. Other than the alignment tool, are there any special tools I'll need to do this job? Once again, any advice is much appreciated.

 

[Haut Medoc]

Re: Mercruiser couplers...3 in a year!!!

What bellows will you need to loosen other than where it connects to the y pipe?.....
A boat engine is generally far easier to R&R than a car....
I can't think of anything special other than the alignment tool....​

 

[goblenick]

Re: Mercruiser couplers...3 in a year!!!

If its easier than a car, then I should have no problems doing it within a few hours. I haven't had time yet to look at the manual to see what all it takes to pull it, and I guess I'm just speculating in worrying about pulling bellows loose. I've only performed a few random tasks on my boat so far and was too intimidated to attempt this last year...now I wish I had. Hopefully I'll start over the holiday and let you guys know how it goes. Thanks again.

 

[daleatskiworldorlando]

Re: Mercruiser couplers...3 in a year!!!

Hi, goblenick and the group.

"I have an "89 Sea Ray with a 4.3 Alpha One (gen 1) drive."

That is old enough in my opinion, and especially if the boat has been kept wet in the water or maybe on a trailer but parked outside to have developed major stringer rot. If I was working on this boat the first thing I would do is take a small hammer and start tapping away at the stringers and especially around the engine mounts listening for soft spots.

My guess is you will find soft spots and your engine is moving around causing the coupler to fail.

Down in hot humid Florida I see this all the time.

Hope this helps, Dale

 

[goblenick]

Re: Mercruiser couplers...3 in a year!!!

I actually just got off the phone with a local marina here and he said the same thing about the stringers. I went to look at the boat real quick and didn't notice any rot (untrained eye), but the forward starboard engine mount was loose...and I mean LOOSE. I also found a 3/4" drive swivel socket (same size as the mount bolt) in the middle of the bilge under the engine. Coincidence??? Anyways the forward bolt on this mount was backed off roughly 7 turns. What would cause this? As far as I can tell, the rubber on the back mounts feels like new. I'll probably still replace these while I've got it out though. Once the engine is out, how hard of a job is it to fix a cracked/rotted stringer if that's the case? The local marina says a few grand which I don't have.

 

[Don S]

Re: Mercruiser couplers...3 in a year!!!

If the mount was loose again, it wasn't tightened down enough, or the locking tabs weren't bent over, or they don't exist. But a loose mount, will cause you to loose a coupler.
If you do find the stringers are rotten, the transom is probably rotten also. The Boat Restoration and Building forum is the best place you could post your question.

 

[Jeremy420]

Re: Mercruiser couplers...3 in a year!!!

Goblenick.. Just another thought, I think that starting the motor with the lower unit in the trailering range can also take out a coupler.. I see lots of people start their engines with the outdrive in the trailering range.... not good!! I thought that's what caused mine to go out.. when you start it the u-joints start binding, then the coupler starts getting stressed and the rubber insert fails after a while..??

The hard part is getting a cherry picker that can raise up high enough to get the motor out.. you may need to let the air out of the tires to get enough clearance or something..

Good luck

 

[goblenick]

Re: Mercruiser couplers...3 in a year!!!

After some further investigation this weekend, I've determined that the transom is indeed rotten. The whole lower half sounds dead when hit with a hammer and there is a lot of flex in it when I push down on the outdrive. There's even cracks starting in the gelcoat just below the outdrive from moving so much. I guess I'll be posting in the restoration section till I have the time to start replacing it, or try and buy another boat and salvage what I can from this one. Thanks again for all your help guys!