New Gaskets blowing on intake manifold, yam mariner 30hp

[papajoe]

Yet another problem with my dam engine, So far I have rebored and replaced pistons, rings, all gaskets, stator, cdi and coil so its pretty much a new engine.

The latest problem I have (new day new problem) is that it won't start because the intake manifold gasket is failing and losing compression and fuel out the side. The engine has really good compression but its too much for the gasket.

Should I cut one of my own, the failure is on the bottom lefthand side.

Heres the breakdown 30A Mariner Outboard 689-550101 AND UP INTAKE MANIFOLD Diagram and Parts

part 18 - 80569M

I'm in to deep to scrap the engine, so what can I do? It has run since the rebuild.

[Davie]

Have you got the bolts mixed up and they are bottoming out?

[papajoe]

Nope, double checked bolts all look good and correct, had it off 3 times today, all cleaned and replaced with a new gasket I picked up down the road. The new one was blowing within 20 seconds of cranking it over? Driving me mad would be an under statement!

[A1an]

Have you got a picture of the mating surface?

[papajoe]

Ok, removed bolts ome by one and added a washer behind them just in case, started it and same issue so stripped it again and the problem is staring me in the face. Even though it's a yam made mariner 689 and all parts are interchangeable, it appears that the profile of the intake of the crankcase is very slightly different between both models. in the very bottom left the yam/mariner casing is straighter than the yam gasket (hard to get mariner one) and there's the problem a little gap of 4mm. Bugger!!!

[papajoe]

ha ha ha ha, this is why I love secondhand outboards, fixed the air leak and couldn't work out why it wasn't starting. The bloody woodruff key had split in half and moved the timing out! Anyway started first time, ran lovely and now shat a bearing. Time for a tear down again!!!!

[Fstarocka]

Oh my.. Well was in the same boat with a motorbike last week.. Three top end head gasket jobs oil and water mixing, previous owner had half unscrewed three of the 5 core plugs!! I JUST saw the bubble as I bent down to pick up a tool.. Was about to tear the whole motor down!!

Screaming now at last! Not only boats trust me!

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[papajoe]

Good to see others suffer as well

[Fstarocka]

Haha yes indeed.. Comes with the territory lol

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