1978 mercury 1150 leaking milky water/gas out of plug hole

[deucex420x]

Bought a new to me mercury inline 6 1978 model 1150.
I was having trouble with no combustion on number 5 cylinder.when I take plug wire off each one at idle it bogs gown except number 5.The boat mechanic I took it to said it might b the reeds and just go run it.I brought it home to double check I was getting spark ran it on the muffs I guess I didnt get the plug tight and noticed a light flow of milk coming out.Any suggestion on where to start.It has 120 compression on 1 thru 4 and 5,6 are 112

 

[Chris1956]

Re: 1978 mercury 1150 leaking milky water/gas out of plug hole

Sounds like a water leak into cylinder #5, likely from the inner water jacket cover, under the exhaust baffle. If this is a freshwater motor, it is likely the gaskets went bad. If saltwater motor, the inner waterjacket cover or baffle could have rotted out. If the motor is and was used in fresh water, you will have a chance to get the bolts out without breaking them.

 

[deucex420x]

Re: 1978 mercury 1150 leaking milky water/gas out of plug hole

Its afresh water motor.Is there any way to inspect the reeds without splitting the block

 

[Faztbullet]

Re: 1978 mercury 1150 leaking milky water/gas out of plug hole

Bottom crankshaft seals bad and sucking water.....

 

[Chris1956]

Re: 1978 mercury 1150 leaking milky water/gas out of plug hole

There is no way or need to inspect the reed valves, without pulling off the powerhead and removing the distributor, starter and crankcase cover. In addition, Waterjacket is no where near reed valves, and stock reeds are very reliable, so ther is no reason to do that work at this time.

If lower crankcase seals are leaking, you should see water in #6 cylinder as well.

 

[deucex420x]

Well I replaced gaskets and it solved the water in cylinder issue,but still cannot get power out of number 5. I checked spark getting a good 1/2 inch,and im getting fuel to number 6. It starts right up but just running on 5.What should I check next

 

[Chris1956]

You first said you had zero compression on #5. Is that still true? Also, on those old motors the spark plug wires go bad. Look for arcing from plug wire to ground.

 

[deucex420x]

I have 115psi on cylinder 5&6 ,1thru4 are120.I also switched out the plug wire on 5 with one of the other cylinders at the distributor and at the spark plug and still nothing different

 

[Chris1956]

Maybe residual water is still in the cylinder? Maybe spark plug is bad? Both wild guesses. Give it a bit of ether in the bottom carb, when running on the muffs. If she picks up, maybe she is flooding? Another wild guess... Have a fire extinguisher nearby.

 

[deucex420x]

Thanks ill give it a try when I get home this weekend. I have put a ton of work in this boat, redone wiring fuel lines put in water seperator, new plugs cleaned cap, new water pump etc....... Im new to outboard so tell me if im wrong but the reeds pull in fuel and then close and expel the exhaust, so could I have a damaged reed not letting it pull air/fuel into that number five cylinder? Or would ther be an obvious tell like backfire thru the carb I hope its not cause I really dont want to split it apart but I have been thru most everything else I can think off. You mention about the carb flooding can it flood only one cylinder since number six seems to be working properly

 

[deucex420x]

Thanks ill give it a try when I get home this weekend. I have put a ton of work in this boat, redone wiring fuel lines put in water seperator, new plugs cleaned cap, new water pump etc....... Im new to outboard so tell me if im wrong but the reeds pull in fuel and then close and expel the exhaust, so could I have a damaged reed not letting it pull air/fuel into that number five cylinder? Or would ther be an obvious tell like backfire thru the carb I hope its not cause I really dont want to split it apart but I have been thru most everything else I can think off. You mention about the carb flooding can it flood only one cylinder since number six seems to be working properly

 

[Chris1956]

Reeds are one way valves. They allow fuel+air to enter the crankcase, as the piston moves toward the sparkplug. As the piston moves toward the crank, the reed valves seal and allow the piston to compress the fuel+Air. The transfer ports and exhaust ports are exposed as the piston nears the crankcase, and the compressed fuel+air transfer around the piston into the combustion chamber, blowing the exhaust out the exhaust port. I damaged reed valve could affect idle operation on a cylinder, but stock reeds are real hardy, and almost never break. Put your hand over the bottom carb and see if the air goes in and out, or just in, as it is supposed to. That could tell you the reeds are good.

 

[deucex420x]

Great explanation, what about the carb only flooding one cylinder is that possible.Is it a bad idea to switch #2 and number 3 carbs out and see if the problem moves to say third cylinder

 

[Chris1956]

I think it possible for a carb to flood 1 cylinder, however, it would be the lower cylinder of the pair. So cylinders 2,4 or 6. Not cylinder 5. Swapping carbs is a waste of time. Why not just fix the bad carb, if it is truly bad?

 

[deucex420x]

I dont think its bad just tryin to isolate the problem with out buying unnecessary parts.My original problem is cylinder 5 is not producing any power.It has a great spark, good compression, and I assume its getting as much fuel as number six is getting and it has me stumped why its not working.what am I missing