Outdrive

MedDreamer

MedDreamer

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Some of you will recall that last year the same part (upper section) of my mercruiser Alpha Gen 2 leg failed on two occassions. According to the company that carried out the repairs the second failure was due to a faulty part provided by Mercruiser. This may be true, and it appears Mercruiser did replace the part FOC, but I still feel that the same part failing twice is more than co-incidence and that the root cause has still not been determined.

In the near future I will be having my boat lifted for antifouling etc. and I am going to ask the company who are doing this (not the same people who carried out the repairs) to check the outdrive installation.

However what should I ask them to look out for? Could it be an alignment issue? I know that they need to ensure the lubricant has been added correctly (ie bottom up) but i am pretty sure this wasn't the issue as I was there when the leg was dismantled after the last failure. Are there any other things I should be asking them to confirm.

Also the Mercruiser drive has a dog clutch which crashes into gear with serious crunching sounds sometimes, can this damage the teeth? and could this result in the failure

Any suggestions would be appreciated.

Martyn
 
Can you be a bit more detailed on 'upper section'. Which bit of the 'upper' is failing?
Generally a drive misalignment damages the coupler on the flywheel, not the upper drive itself. Is the idle speed of the engine set correctly, and is the cutout switch that momentarily cuts the engine when you engage and disengage operating correctly? One mistake many people make on the alpha and on outboards is to 'tickle' them into gear too gently. On these types of gearboxes without clutches a good positive engagement is the way to go for a long gearbox life. All IMHO of course.
 
It could of been a shimming problem. This drive needs the driveshaft to be shimed at the right height and the UJ assembly shimmed so the driven gear sits into the driveshaft at the correct height. If either was shimmed incorrectly this can lead to premature gear or bearing failure.
The dog is a ratchet type unit when thrown into gear it has slopes then a step when this step hits the flats in the gear it then drives the prop shaft.
It should not damage we have Alpha drives on 500hrs and no probs.....yet!!
 
Alphas tend to lead a hard life. Small sports boats that are used and abused ie the young lads, first boat think they can beach it and knock it about. On the other hand respectable owners like the lovely people here that buy and cherish the boat then upgrade after a year to something else.The hours dont tend to mount up.
The drive and engine will obviously last longer with regular servicing and maintainance who knows what the life expectancy is.
We have a reliance 1995 twin V8 D-Tronics 300hp on Bravo 3`s will 4500hrs still going strong dont be concerned...
 
You needn't worry about your B3 drive so much as it doesn't have a dog clutch shift like the Alpha, it has a cone clutch which is like the synchromesh in your car gearbox, there are no sudden shock loads when you shift providing your idle speed is correct, so it should go for many hours if you follow the service schedule.
 
How old is the boat and how many hours has it done? As the service schedule specifies that the alignment should be checked once a year which is when you would inspect the bellows for leaks. Has the engine been out at any stage as there is a spring under each rear engine mount and this can easily be dislodged when installing the engine. We once had a boat with one missing and the result was a collapsed gimbal bearing which then let the cardan joint rub through the mounting that the bellows are attached to which let in water which got into the drive and rusted the bearings and gears, req'd everything from the transom shield aft replacing, all for a tuppenny spring!
 
I wouldn't worry, it'll probably have fizzled away by then! What you've got to remember is that the "trade" view anything, enginewise, older than 5 years as "clunkers"! or so someone here told me a while ago. I can't be bothered to search for who said it.
 
A non-boaty but mechanically minded friend of mine suggested the same thing, I will raise this specifically with the servicing company.

What is involved in checking the alignment? is a special tool needed?

Thanks for the help

Martyn
 
You have to remove the drive and insert a special tool thro' the gimbal bearing and into the engine coupler which is basically a dummy drive shaft which enables you to align the engine with the gimbal bearing, a bit like a clutch alignment tool if you have changed a clutch on a car.
 
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