Mercury 850 engine, knocking noise and flywheel shaking. Upper bearing problem?

[eggcanada]

Hi all, I just bought a boat with a Mercury 850 (1973) engine on it. I have read many helpful posts here. I have rebuilt carbs, starter, fuel pump and the engine is running. My question is, is the knocking sound a serious problem? I see the flywheel is "shaking", does it mean that the upper bearing is gone?
Thanks!

 

[fhhuber]

Something seriously mechanically wrong and the potential list includes:

Bent rod, twisted crankshaft, bearings, (just about any of the main bearings), Someone shaved the heads to the point they are getting it by pistons, Extreme bad timing to the point of severe detonation (which can eat holes in the pistons), Inadequate oil (maybe complete lack of oil) for long enough to cause major damage.

Possibly a combination of 2 or more of the above...

Whatever it is... quit running it until its fixed. because its tearing things up. that noise is metal hitting metal in a bad way, or severe detonation (or both)

 

[Faztbullet]

Looks like lower crank bearing has chit allowing excessive crank end play, Stop running it as ball bearings can/has entered cylinder and you will need to replace lower reed block as labyrinth seal are damaged from crank flexing...I have seen this happen after someone poisons the motor with a overdose of a decarbon treatment

 

[racerone]

Well, there is no cylinder head on this motor.---So that theory is mute.----Look into issues with the flex plate on the flywheel or a broken crankshaft.

 

[eggcanada]

Thank you everyone! I know this is a bigger problem. I did presure test, 1, 2, 3 are around 150 psi seems good. I didn't test 4 as the hose connector couldn't reach it.
Also, some dark grey milky liquid coming out from the exhaust port after the engine was running for few minutes.

 

[GA_Boater]

The milk is unburned pre-mix and water.

I can't add much based on experience as the guys in the prior posts did, but I tend to start simple before tearing into motors.

Have you checked for spark on all four plugs? This one may be a stretch, easy to check - Are the timing marks lined up when #1 is at TDC?

 

[Chinewalker]

I would start by checking the flex plate on the flywheel. They have been known to crack at the center hub.

 

[merc850]

It almost seems like some plug wires are not on the right plugs, the firing order is 1-3-2-4. Do not run engine with ungrounded plugs. Where do you live?

 

[eggcanada]

It almost seems like some plug wires are not on the right plugs, the firing order is 1-3-2-4. Do not run engine with ungrounded plugs. Where do you live?

I live in Scarborough, Toronto Ontario.

Thank you all! I will check the flex plate.
I'm pretty sure the wires are in right order. This engine parts are in good condition, it seems it wasn't used much but was not well maintained.

The plugs are in good shape, every easy to start, just some grey milky thing on them after running for a while. I'm not sure if that's gas or water...

 

[Faztbullet]

I have to say in my 40 years of working on motors I have never seen a broken crank on a Inline4 motor, Inline6 and 402's a plenty.....