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Old 02 February 2009, 06:06   #1
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Blown bearings on Merc 75hp

Hi All,

Following on from my disaster off Knott End on the 2nd of Jan, I've now stripped the engine down to find the source of the problem, see pics attached. Clearly the bearing is shot, plus there is a hole to size of two fingers in the crank case, doh. I have a friend who thinks he may be able to get the crank case welded for me, can anyone advise where I can get a bearing from?

The engine is a Mercury 75hp, 3 cyl from around 1884.

Still don't know what caused this yet, or what put the hole in the crankcase. I got stuck at the point where I needed to get the flywheel off as I need a puller. Just for completeness here, there was still plenty of oil in the oil tank, plus oil in the pipes to the engine, and the the other two cylinders are fine, bearings are moving freely by hand.
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Old 02 February 2009, 06:09   #2
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That would be 1984 not 1884 :-)
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Old 02 February 2009, 06:59   #3
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Bearings Rebuild Opps

I did a similar thing on a 90hp mercury.

It wrecked the crank, so I would suggest tacke of the rod, check the crank first, clean it up with emery cloth, and then measure the ground crank surface.

I got sets of bearings from the US cheaply, from THE OUTBOARD EXCHANGE, they were really helpful and quite cheap, you can but each individual part.

They do cranks , blocks gaskets , rings , pistons ect , etc.

Rememebr you should really put in new conrod bolts and they are about 10 each, I may have a new set from a rebuild I did unused if youre interested.


If you rebuild it, get a blank from them for the oil pump and run it premix, to avoid future trouble.

P.S My crank had severe damage as I had to run the engine to get in to safety, but yours might be ok of you shut ti off quickly.

P.S NS Marine had a whole 80hp power head for about 350?

Hope the rebuild goes ok.....

Chris
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Old 02 February 2009, 07:53   #4
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Hi Chris, thanks for the advice and the PM. Once I get the flywheel off and see the damage properly I should be able to make a decision re rebuild or abandon. I'm away from next Monday for two weeks, so it could well be early March before I can get back to you re your PM. Definitely interested if the damage is more extensive etc., plus I need to price up gaskets, bearings, crank case fix as well.
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Old 02 February 2009, 08:07   #5
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Hi Chris, thanks for the advice and the PM. Once I get the flywheel off and see the damage properly I should be able to make a decision re rebuild or abandon. I'm away from next Monday for two weeks, so it could well be early March before I can get back to you re your PM. Definitely interested if the damage is more extensive etc., plus I need to price up gaskets, bearings, crank case fix as well.
Hope all goes well Neil
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Old 02 February 2009, 08:17   #6
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Cheers Pal, will be good to meet up when I'm up and running, if only so I don't need to bother the coast guard again if I conk of knott end :-)
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Old 02 February 2009, 08:31   #7
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Cheers Pal, will be good to meet up when I'm up and running, if only so I don't need to bother the coast guard again if I conk of knott end :-)
Look forward to it. Could have done with you at Knott end last week when the winch snapped, broke me finger, was threatened with a 2000 fine by the ferryman for blocking his path and a call to the police because my car was on the slip too long!
Put me off that much I eveb thought of using the Stana slip next time
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Old 02 February 2009, 09:09   #8
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You could easily end up spending more on the repair than the engine is worth, however how about a trip to Weymouth:

http://cgi.ebay.co.uk/Mariner-75hp-o...1%7C240%3A1318

Can't see him selling it for the asking price, however grab his phone number and contact him afterwards.

Pete
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Old 02 February 2009, 09:19   #9
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You could easily end up spending more on the repair than the engine is worth, however how about a trip to Weymouth:

http://cgi.ebay.co.uk/Mariner-75hp-o...1%7C240%3A1318

Can't see him selling it for the asking price, however grab his phone number and contact him afterwards.

Pete
Not a bad idea. I'd take your starter and spin it up with a compression tester though-it'd be a bugger if he'd taken the starter off to hide that it's dead.
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Old 02 February 2009, 11:00   #10
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Thanks for the advice, and I agree it could well cost more than its worth to repair this engine. Bit more investigation though to make the decision. The engine was very clean, and an absolute breeze to take apart, no stripped bolts etc, it has clearly been well looked after previously
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