Merc 80 still leaking?

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Alacrity
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Re: Merc 80 still leaking?

Post by Alacrity »

Just a thought, & we may have spoken on this before, did you have the inner water jacket off? It is under the exhaust baffle & goes around the exhaust ports. This has water passing through it as well.
Mercs are like women, no 2 are exactly alike. That's what testing is about. In general it is safer to test motors and props than women!

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floater
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Re: Merc 80 still leaking?

Post by floater »

Tickover was set in the tank, prop turning (feet and trousers getting wet) any richer and out of gear it was barely able to keep going it was so rough weaker ran smoother but stalled going in to gear.

Inner baffle is new, it was fitted to the original motor when I got it probably by someone on a similar quest. The block is now a diferent one to the original so I used the new inner baffle on it as the one fitted was badly corroded and cracked during removal. the inner baffle was fitted using new gaskets and threebond sealer on threads and faces. the outer and inner exhaust covers are also new parts again threebond and new gaskets.

Had a look at my spare leg and old block trying to understand the water flow path. I cant work out how water spits out of the two slots at the top of the leg at the back as there doesn't seem to be a direct path, however all Mercs of this type do it so it must be right, I just don't understand how,

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Re: Merc 80 still leaking?

Post by haventaclue »

That leaves only water ingress :console: And the only thing I can think off is that there is a hairline crack in the block or one of the pieces that you used from the original block, that opens as the engine gets hot and the aluminum expands :hmmm:
floater wrote:threebond sealer on threads and faces.

I haven't heard of this stuff,is it something like "Pro" Marine gasket seal.
Stuff I bought in the "States". Well I was there and it was a lot cheaper than stuff that I could get here. :D The security person at the desk in JFK took a very long hard look at the X-ray scan. Nail guns ,hammers,spanners,worm drive,wiring looms et. etc.etc. :hilarious: :hilarious:
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floater
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Re: Merc 80 still leaking?

Post by floater »

A crack is the most frightening scenario. I did pressure test the block when it all went together and it tested ok. However the only way I will be sure is to pull it all apart and test it again I guess. Or run it and pull it apart quick before all the evidence dissapears.

The Three bond was a recommendation from Alacrity, available here:-
http://www.ebay.co.uk/itm/THREEBOND-LIQ ... 5ae49d85d8

haventaclue
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Re: Merc 80 still leaking?

Post by haventaclue »

Another way would be to set up with the air in and then gently heat the block with a heat gun to simulate the running temperature.
Must remember that Three Bond liquid.Thank you :thumbsup:
no matter how bad it is,it can always get worse,I'm an optimist

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Re: Merc 80 still leaking?

Post by floater »

Am I correct in thinking that the only place the block could be cracked to allow water in would be the cylinder head as everything else is covered by the cylender liner?

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Re: Merc 80 still leaking?

Post by haventaclue »

http://www.marineengine.com/boat-forum/ ... nextnewest .Along the same lines.
I'm wondering if you had the surfaces skimmed,might solve the problem.
I believe if there was a crack opening behind the cylinder sleeve,it would run to the bottom and into the crankcase.Unless it's right beside the intake port.
no matter how bad it is,it can always get worse,I'm an optimist

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Re: Merc 80 still leaking?

Post by floater »

Hmmm need to go looking deep then.

Whilst removing the bolts for the baffles I managed to break a couple so had to drill them out, whilst it was all set up on the mill I took the oportunity to skim the surfaces, those that were'nt machined were given a good wipe across some abrasive on the flat bed.

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Re: Merc 80 still leaking?

Post by haventaclue »

I know I said there may be a crack which might open under operating temperature,but after rereading your post "Merc 80 she lives", and read this, "loaded the assembled crank with all new piston rings into the (spare) block".I don't think that is your problem.Unless you are the unluckiest man alive, :) As Alarcity says,cracked blocks on these engines are very rare
Maybe a re-torquing of all of the bolts,including those in the water jacket/inner baffle.
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Re: Merc 80 still leaking?

Post by Alacrity »

To save me re-reading the thread what, if anything, apart from the rotating assy, is from the original motor? The other thing you could try, although it would mean pulling the powerhead, is to pressure test it again, but warm up the block as hot as you can (within reason) & see if it still holds OK. Are you positive you have water getting in & are not just being (understandably) paranoid? :console:
Mercs are like women, no 2 are exactly alike. That's what testing is about. In general it is safer to test motors and props than women!

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