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Mercruiser gearbox failure

jesses

New member
Hi,

We had a bit of a drama out on the boat yesterday and I am trying to get a better idea of what might have gone wrong. Any help is appreciated!

Mercruiser 5.0L with stern drive. While maneuvering at slow speed there was a strong smell of burning clutch and then the boat would not engage forward or reverse gear, the linkage was jammed in the central neutral position.

What is likely to be the failure and what is involved in replacing gearbox components in a stern drive? Does the motor need to be removed or can these components be accessed from the stern? Is this type of problem usually caused by something jamming the prop or normal wear?

Regards,
Jesse
 
1 Check the oil level and condition
2 Let us know the results
The drive can be removed for service. no need to touch the motor.
 
Well a Stern drive doesn't have "clutches" to burn, but it does have a "Engine Coupler" that will burn and smoke and when it does, you can engage into forward or reverse but it wont do much or anything, especially in the water... and if it's really bad, nothing out of the water.

To check before removing the drive, with the boat running and in the water, and tied to a dock, put the boat in gear and look to see if the shaft coming out of the BACK of the engine is turning, If not.. engine coupler. If it is.. then you've got something else bad. ( but the outdrive doesn't have clutches like a car/truck and wont' Smoke unless highly overheated - at that point burning the paint of but I would think the bearings & gears would be destroyed at that point. )
 
'the linkage was jammed in the central neutral position.'

But this would not happen with a burned out coupler???

My guess, is a combination.
Drive seized, coupler overloaded and burned out!
 
'the linkage was jammed in the central neutral position.'

But this would not happen with a burned out coupler???

My guess, is a combination.
Drive seized, coupler overloaded and burned out!
Given the above, "Ockham's Razor" may come into play here!

This is near impossible to diagnose on the forum. You will want to pull the boat and do some testing.... and possibly remove the drive!
From there you may be able to determine the condition of the coupler splines by inserting the alignment tool in hopes of seeing, or not seeing, metalic residue!
The rubber coupler hubs generally don't let go from the smaller engines, but the splines may if the drive locked up and/or if the engine alignment had not been routinely performed!
Strange that this would wait and occur at low speeds! :confused:
 
""Ockham's Razor" may come into play here! "

hmmm. The simplest explanation.

Burning smell followed by jammed gear selector.

The gear select cable has melted onto the exhaust tube and jammed up gear selection. JM2CW. Mark.
 
Would " Ockham's Razor " demand all the known facts be presented before a theory was put forward for a solution ?

So tuna my man, my main man tuna, you suggest what, as to finding the solution? Removing the cable at the converter, and then moving the lower cable to see if it shifts ?

Wouldn't that be better then posting some obscure theory, and giving no explianation of said theory.

Or was posting such theory with no explaination a way to show your superior intellect ?

I can believe the cable melted cause it was coming into contact with the riser or mani. I don't think the mani, gets that hot, or the riser to melt the cable but could be.

Could be a freekin alien droped into the guy's engine room and the heat from his spaceship f--king melted his cable could be.

Could be the cable was somehow in contact with a pulley, and the freekin pulley melted his cable.

I think BT Docture has enough expierence that would suggest his theory is more plausible. Why ? Cause he probably seen this chit before.

Why the burning smell ? Hmmmmmm the drive froze for whatever reason and the coupler, started to spin the rubber part that is, hence the smell.

Why would the drive freeze hmmm water in the drive maybe, and then a gear went and wola frozen drive, upper maybe, maybe lower hence the" clutch " dog can't do whats dog's do go back and forth.

Drives do have a clutch but it's not a auto or bike clutch but still a clutch.

Enough with thhis Razor crap from some guy in the 12th century that didn't even come up with the theory. Yea i heard it before, some guy tried that stuff in aircraft school 40 years ago, he too was told to cut out that razor crap.
 
Couplers do fail even when the drive hasn't "locked up". If the shaft ian't turning, it will not shift into gear. Look closely in the area where the shaft goes into the back of the engine - often there is rubber dust that has been slung around = coupler failure. None there? Pull the drive and check the splines - metal particles, rounded corners = coupler failure.
 
My coupler went no rubber on it all metal and yes they go without the drive freezing, and or hitting something with the prop.

What year this drive and motor?
 
A whole lot of answers but no reply from original poster...........maybe let this one go until we hear back.

Opinion are like.................U know what!
 
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