mercruiser 4.3 i/o stern drive keeps exploding engine couplers

[nitemare38]

We have bought a 2001 Suntracker party deck 21ft 4.3L Mercruiser stern drive and welove it except for one problem. In the 6 weeks we have had it we have had to replace the rubber engine coupling 3 times. At over $1000 this is the last time we are doing it unless we find the root cause. We only run the boat at 2800 RPM or less. Each time it has burnt up the coupling we have been in a straight line in 25ft+ of water. This is the 2nd mechanic, and I really trust him and he is sworn to not stop investigating until we get a root cause. Each time it happens we are running about 26mph and less than 3k on the tach. It just jumps up in RPM and smells like a burnt clutch. Then we get towed back and look and the clutch is disintegrated. It is my opinion that something in the mercruiser stern drive is "in a bind" and putting too much pressure on the rubber clutch. FYI, this boat was only put in the water 6 or 7 times by the previous owner, a 70 yr old man. Engine looks pristine and purrs like a kitten, no vibration at all, until the moment that the clutch explodes. Please if anybody has any ideas, we are not going to run it again until we find the issue.

 

[Don S]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

Time to be looking at engine alignment and what is going out on it. Was the alignment checked at all?
Are the motor mounts loosening up because they weren't tightened or locked in place?
Is the transom or the stringers dryrotted? that would cause everything to flex and change the alignment.
Is the hull flexing?
So many things can go wrong, and we can't physically look at it up close.

 

[nitemare38]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

Engine was aligned properly, motor mounts are good.
How would we find out if the hull is flexing ?

 

[HT32BSX115]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

Howdy,


A 2001 model is more than old enough to have rotted stringers/transom loose engine mounts, etc to cause mis-alignment.


Did that boat EVER sit outside and fill up with rain water? Did the mechanic check for alignment and rot after the first (or 2nd coupler failure?

You'll probably find something like that going on. My last boat had a coupler that lasted 39 years before I replaced it.....



Good luck!


Rick

 

[nitemare38]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

Boat has never been rained on, until we got it. We keep it in the dry but have gotten caught in the rain on the lake once, we promptly drained.
Hull transom and engine mounts are solid, no welds broken or flexing. Motor and outdrive are alignged each time.

 

[45Auto]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

Is the outdrive input shaft worn or out of spec? If not, seems like that all it could be is either the alignment is changing or something in the outdrive is binding up enough to strip the coupler. No other way to load it enough to strip it.

 

[Howard Sterndrive]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

watching the engine for movement while someone else drives all I can think to suggest.

I was selling a cruiser years ago, and was surprised when the buyer's surveyor pointed out the weak engine mounts boxed on to the stringers. He said they were flexing on our test run. I thought he was full of baloney. So he drove and I watched, and yeah...that engine was twisting them pretty good. They were boxes of glassed plywood basically.
I had to fix it for the sale. He was a good surveyor.

 

[Bt Doctur]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

Try replacing the rear motor mount bushings

 

[m_87]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

if you can i would try to get in contact with who you bought the boat from in sure it was an as is sale but just tell him whats going on and see if there was anything he did to the boat or had someone else do to it that could give you a good idea. maybe the did maybe they didnt.. some people get into a boat thinking they can fix it and cant so they put it together best they can and sell it. so they if they did they might not admit it. or some good people out there will admit it and give you any information they can to help you and your mechanic fix the problem

 

[nitemare38]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

Well everybody, I just found out the bad news.
Actually it's partially good news, at least now I know, the reason the coupler was failing is the stern drive was in a bind. Cant be turned even with a wrench, foot oil smells burnt and has metal in it.
I asked the mechanic what needed replacing, he said everything, it is so bad he recommends replacement.
So for my next question, where can I find the best deal on a alpha1-gen2, with a 1.8 gear ratio. I would like options on new, re-man, used, or aftermarket ??
Other small bit of good news is the dealer is covering the coupler, even thought it wasn't the coupler's fault.
Thanks in advance for all your replies.

 

[Fishermark]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

Sterndrive engineering outdrive - sold here on Iboats. Without question it is your best option.

 

[Howard Sterndrive]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

If the outdrive was seizing up, wouldn't one hear/feel the engine go under extreme load just before the coupler let go?

 

[boat127]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

after the alignment is donw turn the engine in 90 degree increments and re check alignment. if it changes then you have a bad coupler and new ones do come bad at times. i had 2 bad new ones at one time for the same boat

 

[nitemare38]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

Update: New Unit from SEI, upper and lower (I highly reccommend the sprinkler for the upper unit). Runs great, past our break in period now, we have probably put 30 hours on it since the foot oil change. Nothing but good things to say from me about SEI. Thanks for all the advice guys. Getting twice the gas mileage I was before.

 

[Fishermark]

Re: mercruiser 4.3 i/o stern drive keeps exploding engine couplers

Good to hear. Good luck!