71 Merc 800 - Check out this bearing, what's left of it.

Project started out just changing the lower crankcase seals because I was getting water into the #4 cyl. After removing the powerhead I proceeded to pull the lower cap and this is what I found, just as you see it.



There are at least 5 balls missing from the bearing and the ball cage is all but gone except for this piece of shrapnel remaining. The motor ran fine except for a stalling problem when shifting into gear. Where did all the pieces go?

With a little wiggling, the outer bearing race came free and the balls spilled out leaving just the inner race pressed onto the crank. So, what's the best way to proceed now? I'm assuming I need to split the crankcase in order to replace the bearing? Any other possible damage caused by this destroyed bearing?

Anyone know the generic bearing number I need as a replacement? I know the Merc part is probably 2 or 3 times the price of the generic one.

Re: 71 Merc 800 - Check out this bearing, what's left of it.

After looking up the new bearing part, I could see that all the balls were there (9 pieces) but the entire bearing cage is missing.

Re: 71 Merc 800 - Check out this bearing, what's left of it.

As it is the lower end ball bearing, P/N 30-63742T, the generic bearing number should be 6206 and you should be able to see this lightly printed on the rim of the outer race. I believe that the 6206 is about $7.00 per brg.

Gerry

Re: 71 Merc 800 - Check out this bearing, what's left of it.

I'm assuming I need to split the crankcase in order to replace the bearing?

Click to expand...

You are correct..........

Re: 71 Merc 800 - Check out this bearing, what's left of it.

Thanks for the P/N Gerry.

Before I proceed with the repair I'm interested in knowing if there may be any other damage caused by this defunked bearing. I probably won't know until I take it apart but I'd like to be prepared.

While it's apart, what else is recommended? Compression numbers were really good. I don't mind spending a few dollars on this motor to keep it in top condition.

Re: 71 Merc 800 - Check out this bearing, what's left of it.

I would doubt you are going to find much of a problem as the inner side of the bearing is up against the lobe of the crank and as such the retainer bits would have some difficulty passing through. If they did though, you should see when you get it apart. You should get a pretty good idea if any material passed through the bearing by the condition of the balls and the ball running surface on the inside of the outer race.

If it were my engine, I would replace both end bearings, seals and "O" rings and check that crank play is still within limits with the existing shims. Other than that there is not a lot you can do in there unless you want to pull the crank/pistons assy but you said you have good compression so why mess with it.

The reason I replace both bearings is that over time, if there is one bad one, the load transfer to the other end produces a rough bearing quickly and you can feel/hear it as soon as the bearing is removed.

Gerry

Re: 71 Merc 800 - Check out this bearing, what's left of it.

Very good points, thanks.

Re: 71 Merc 800 - Check out this bearing, what's left of it.

Fast, couldn't you put a puller on that inner race and drag it off the crank? How about some heat to expand it? Crack it off with a cold chistle?

Re: 71 Merc 800 - Check out this bearing, what's left of it.

Now there's a thought. Not sure I could get ahold of it securely or not to use a puller. I could use a gas axe and heat it up really good with hopes of it "sliding" off. Could any harm come to the crank with application of significant heat?

Maybe I should however replace both upper and lower bearings at the same time as Carholm suggested.

Re: 71 Merc 800 - Check out this bearing, what's left of it.

Using a torch is possible, the thing is you want to get the race heated very quickly and off the crank before the heat can 'soak' into the crank.

Liquid nitrogen + cold chisel + good leather jacket, gloves and facemask to protect you from any flying pieces.

Re: 71 Merc 800 - Check out this bearing, what's left of it.

Short of pulling the block apart, is there any way of determining the condition of the upper bearing?

Re: 71 Merc 800 - Check out this bearing, what's left of it.

You could probably make a puller to yank it off but nothing over counter...and I would pass on the open flame torch as you may set off some fuel fumes internally and could cause a major crankcase backfire The bearing s upper and lower are pressed on and you dont want to hammer a new one on anyway, pull crank,replace main bearings, check cylinders and rings .