Mercury 2.5

[onenyala]

I have nurtured my 2.5 for many years however it has suddenly started making troubling noises from the crank case area. Well known outboard retailer/repairer has heard the sound and probably correctly diagnosed the problem as big end/main bearing and condemed it as scrap due to cost of parts and labour.
Irrespective of the cost of a new engine I am loath to dump it. I am reasonably practical. Would it be likely that I could carry out the repair myself ?
A couple of other points:
The problem came suddenly. I used the engine in Dartmouth with no evidence of the noise. When I put the engine on the dinghy to go ashore in Portsmouth two days later it was immediatley apparent.
I had a rope wrap and stalled the engine probably one hours running time prior to the problem. Could this have caused the bearing to go ?
Anybody with a surplus to requirement workshop manual ?
Any comments help would be appreciated.

 

[steve28]

What would you say the noise sounds like ?

 

[VicS]

[ QUOTE ]
I am reasonably practical. Would it be likely that I could carry out the repair myself ?


[/ QUOTE ] Then take it apart and find out what the trouble is. That will be a much more certain way of diagnosing the trouble than asking for a "distance diagnosis" from forum members. Then find out the cost of spares and decide whether it is worth repairing or not. Only you can judge your level of skill. Personally I'd have a go.
A rope wrap should have sheared the shearpin or spun the rubber drive, which ever it is, but you never know.
After "many years" you may find it is difficult to undo some of the bolts in aluminium castings.

 

[Lakesailor]

You certainly can do the job yourself. I have just done the same job. The upper main bearing tends to go first as it is above the rest of the engine and the oil misting it receives drains away. Also heat rises so it dries out more quickly.

I cobbled up a puller for the flywheel from a 3 legged puller

and just undid the back of the crankcase. You can see the bearings are quite tight against the crank cheeks, but two stout screwdrivers as levers started it moving.

This is the technical equipment I used to remove the bearing, just resting the bearing tracks on the vice jaws and using a hide mallet (but rubber would do)

The new bearing drifted on easily using a steel tube to bear against the inner track. I used a bearing without a peg and fixed it with Loctite, but it seems you can get the pegged bearings at a reasonable price.

It's worth whipping the head of whilst you're at it and poking out all the waterways.

and also poke out the water ways under the powerhead gasket

Oh Yes. like Vic says you will snap a couple of studs. Usually the powerhead to leg ones. But carefull drilling-out and re-tapping sorts that.

 

[tross]

The trick to putting these bearings on is to put the crankshaft in the freezer for a few hours - don't tell the SWIMBO and gentle warm the bearing. Normally you will find the bearing just slips on if you keep it in line with the shaft.

 

[Lakesailor]

Mine just slid on with hardly any effort, so I didn't need to go to those lengths.

 

[onenyala]

Thanks to you all for the response - I'm definitely going to have a go !

 

[pcatterall]

Yes that Lake Sailor is so good!! I wish I had that problem so I could follow those loverly instructions!!
Good stuff init.