continuing mercruizer coupler problems, suggestions

adam1psu

Petty Officer 3rd Class
Joined
Sep 25, 2006
Messages
90
well here it goes, first off i am a mechanicaly inclined person but am far from a marine mechanic so go easy on me if i do not use the proper terms for parts. recently i have been considering fixing up a boat I own that has not been run for about 3 years. This is after my bass boat died last week. The boat in question is a 1976(pretty sure anaway) Starcraft 20 ft aluminum, bow rider style with a mercruizer inboard/outboard drive system. it has a chevy 4 cylinder(cast iron block-iron duke to dirt track auto racers) i am fairly sure it is a 2.5 140hp. the engine runs great! it has less than 300 hours on it and the hull is in good shape also. the last summer i had it on the water the coupler that bolts to the flywheel connecting the engine to the splined shaft on the mercruizer drive melted where the rubber is inside the coupler. i replaced the coupler myself. while working on it i noticed that the bolts that mount the wooden engine mounts to the hull of the boat were loose. i figured this is why the rubber burnt out of the coupler because the block wasnt bolted down solid. so i tightened the bolts. i talked to a local marine mechanic who turned out to be a crook, about the problem. he told me to put the coupler in and bring it to his shop so he could line the drive system up with the engine. i thought this made sence. 3 weeks went by with no work done by the mechanic. i showed up to see what was going on with the boat. Even though the trailer never moved from where i left it with grass growing up around the tire, the guy told me he lined it up and charged me $20. next day i was on the lake and the coupler again burnt out.

my questions- is there even a tool to line up the engine and drive system?

what causes a coupler to burn up?

would the loose wooden mounting blocks cause this?

thanks for any help-adam
 

bjcsc

Lieutenant Commander
Joined
Jun 1, 2006
Messages
1,805
Re: continuing mercruizer coupler problems, suggestions

You're thoughts are correct. Sounds like an alignment issue to me and pretty textbook at that...
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: continuing mercruizer coupler problems, suggestions

Yes, there is a tool for doing the alignment. It's a bar that goes through the gimbal bearing and into the coupler. The drive MUST be removed to do the alignment. With the inline engines (Both 4 and 6 cyl) the front mount is adjusted up and down to get the alignment bar to slide easily in and out of the coupler.
The rear motor mounts are another cause for coupler failure. If they are soft or have come apart it will let the back of the engine sag, boom, another coupler gone.
You can get the alignment bar on ebay, or you can buy new, or even make your own if you have a metal lathe.

Here is a link to a free online Merc manual, it's for a newer drive than yours, but some of it is about the same.
And may help you get an idea of what is going on.

http://www.boatfix.com/merc/Servmanl/6/6covr3.pdf

Here is some more great info for Mercruisers.

http://www.mercstuff.com/howdoi.htm
 

adam1psu

Petty Officer 3rd Class
Joined
Sep 25, 2006
Messages
90
Re: continuing mercruizer coupler problems, suggestions

thanks! anybody have a basic estimate on what a marine mechanic would charge to install a coupler? i am sick of working on my own stuff! :^
thanks
 

Haut Medoc

Supreme Mariner
Joined
Jun 29, 2004
Messages
10,645
Re: continuing mercruizer coupler problems, suggestions

Probably about 8 hpours...
Gotta R&R the engine to replace it.....
If you did it once you are now a pro...:):)
Replace it again & do the proper alignment....
One thing that you should check is the integrity of your transom, if you have a problem with flex it could cause a problem.......
My guess it is that was never realigned or the bolts came loose again..........JK
 

adam1psu

Petty Officer 3rd Class
Joined
Sep 25, 2006
Messages
90
Re: continuing mercruizer coupler problems, suggestions

lol... thanks for the info:)
 
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