mercruiser coupler substitution steel vs aluminum

[the man]

Recently I replaced the coupler in my 5.7/Bravo 3 set up, and in another thread here a gentleman suggested that I substitute the coupler that is made of steel vs. the stock aluminum since this was my second coupler to go out in 2 years. This worked great, and the substituted part even has a zirc fitting that is easier to get to. Now I have another boat that needs a coupler, and a couple questions regarding this one:

1. It is a 2005 4.3L Mercruiser with an Alhpa one outdrive. Closed cooling, 190 hp, TKS. Engine serial # OW311876. Note: on the engine, it says Nov 2004 production. I cannot find in the engine manual or the outdrive manual anything about the coupler and/or a part number. Am I blind or is this information somewhere else?

2. Can I make this same substitution in this set up? The upgraded part number for the 5.7/Bravo 3 set up was Coupler 861523A11. Will it be this exact same part for the 4.3/alpha one? If not:

3. Related to first question I guess, but where do I find, and what are, these part numbers; both for the stock replacement and for the steel upgrade (if available)?

Thanks

 

[Bt Doctur]

Re: mercruiser coupler substitution steel vs aluminum

The OEM will work for a lot of years ,have a couple of 15 year ones still going strong.
IF and only IF you remove the drive every year to check alignment. Couplers go bad from mis-alignment or lack of grease . You either have bad rear bushings, loose front motor mounts that change the alignment, or bad/rotted engine bed stringers allowing the motor to torque over.Greasing the zirc on the coupler WILL NOT save it IF your engine alignment is changing.Even of you found a Titaninum one,it would still fail.

 

[the man]

Re: mercruiser coupler substitution steel vs aluminum

I have been paying to have alignment done every year. When I replaced the coupler the second time in the 5.7/bravo 3, I did it myself. After installation, I lifted the front mount over an inch from where it was to get the alignment right. From now on I do it myself.

In this particular boat (the 4.3/alpha one) I paid earlier in the year to have this checked (alignment). Judging from the work he did on some other issues, I would not be surprised if he either did it wrong or didn't do it at all. Either way, I have to replace the coupler now. The boat is relatively new, (150 hours) fiberglass with no rot, and engine mounts are tight.

 

[Bt Doctur]

Re: mercruiser coupler substitution steel vs aluminum

At the very least ,replace the rear bushings

 

[Bondo]

Re: mercruiser coupler substitution steel vs aluminum

Ayuh,... Odds are, that 4.3l already has the coupler you're looking for...

 

[the man]

Re: mercruiser coupler substitution steel vs aluminum

At the very least ,replace the rear bushings

I assume that you refer to the motor mount bushings? Note taken- will do.

 

[the man]

Re: mercruiser coupler substitution steel vs aluminum

Ayuh,... Odds are, that 4.3l already has the coupler you're looking for...

Already has the steel rather than aluminum? Okay- same part number as for the Bravo 3? 861523A11?

If so, that shoots down my theory that the steel may last longer.

 

[achris]

Re: mercruiser coupler substitution steel vs aluminum

The material the coupler is made from has no bearing on its longevity. The first engine in my boat was a Merc '165' (aluminium coupler). Was 22 years old when I took it out, and the coupler was still as good as new. The next engine was a V6 (1994, 4.3LX), I kept that for 12 years before selling it to a friend. I installed it and I still maintain that engine and it still has the original coupler (now 16 years old).

As long as the alignment is right and the splines greased the coupler should last many, many years. If you are chewing up couplers, then look for a problem, not at the coupler material.

Chris........

 

[the man]

Re: mercruiser coupler substitution steel vs aluminum

As long as the alignment is right and the splines greased the coupler should last many, many years. If you are chewing up couplers, then look for a problem, not at the coupler material.

Decent advice and it makes sense.

Does anyone know where to find these part numbers? As stated earlier, I do not see the assembly in the engine or the outdrive manuals.

 

[Bt Doctur]

Re: mercruiser coupler substitution steel vs aluminum

http://www.mercruiserparts.com/Show...br=1937&bnbr=170&bdesc=CRANKSHAFT+AND+PISTONS
you will need the serial number to be sure.normally listed under "crankshaft" section.