Mercruiser - water in oil and misfiring

[jmicara]

I have twin 2001 Mercruiser 5.7 V8 Thunderbolts. I recently heard a strange pinging noise while doing 5 mph going through a canal. I looked at my gauge and saw that I was overheating at 200-210 degrees. I shut that engine down returned with the other one.

I noticed a coffee-beige colored substance on the bottom of the boat and later found out it was oil that mixed with water. The dip stick showed the fluid levels to be within range but there is definitely oil on the bottom of the boat that leaked from somewhere. I also have a small amount on the engine block near the distributor cap...maybe a shotglass full. I can't tell where it is coming from. Gasket?

I changed the plugs to see if there was any water in the chambers and they were dry. I changed the wires and the distributor cap and rotor. Same misfiring sound that gets worse as I rev the engine. After doing a lot of research online I think it might be my risers but I'm not sure why it would be leaking and from where. Any and all help would be greatly appreciated.

Thanks in advance,

Joe

 

[Bondo]

Re: Mercruiser - water in oil and misfiring

Ayuh,... I'd have to guess you have Several things goin' on,...
Like a Bad Impeller, or water restriction causing the overheat,...

As for the Noise,... Run a Compression Test,.. That might lead you in the right direction...

As for the Oil Leak,... Ya just gotta LOOK,... Oil, like Water, flows Downhill...
Start down low,+ work Up to the highest point you find Oil,...
That's where the Leak is...

 

[jmicara]

Re: Mercruiser - water in oil and misfiring

Thanks for the reply Bond-o!

I forgot to mention I disconnected the hose to see if the outdrive was pumping water and it is...very strong in fact. So I'm still puzzled as to the overheating. I'd like to think it was seaweed but I somehow doubt it.

I definitely need to locate the leak but the engine compartment is so tight that my mechanic now gives me as much advice as possible for fear I might ask him to do the work. Seriously, he owned this show with his Dad and worked their over 50 years and can't believe how tight the area is. I might consider removing the wall in the aft cabin which is right behind the engine compartment. This should provide better access.

So based on your response, do you think I'm off base with the riser? Would that cause water to get into the oil? Also, what else could be causing the misfiring?

I'll try again this weekend to see whats going on.

Thanks again,

Joe

 

[badger42]

Re: Mercruiser - water in oil and misfiring

Suggestion for finding the oil leak- I picked up one of those "see-snakes" from the hardware store (about $100) to locate an oil leak on my engine. worked great, can use it while the engine is running. It also located a small power steering leak in the process.

 

[jmicara]

Re: Mercruiser - water in oil and misfiring

Great idea! Thanks!

I looked online and saw the Ridgid model from the Home Depot $200+ and a Milwaukee model from Amazon for $100. The Milwaukee model was reduced from $284 to $100.....makes me wonder why. Do you have the Milwaukee or another model.

Thanks again for your suggestion.

Joe

 

[badger42]

Re: Mercruiser - water in oil and misfiring

I got the Ridgid micro at Home Depot while on sale for $100. Ridgid comes with a lifetime warranty; not sure about Milwaukee, but the price sounds ok.

 

[jmicara]

Re: Mercruiser - water in oil and misfiring

I had another fun filled day with my boat today.

I took all the spark plugs out and did a compression test on each one. All came up within range 140-150. I thought I found the problem when I noticed a spark plug was slightly cracked by the porcelain stem. I changed and the same sound.

I then had someone else listen to it and they believe the noise is mechanical, not a misfiring. I was told to poor Marvel Mystery Oil into the crankcase and it might free up something that sounds stuck.

If oil leaked out and was replaced by some water, could it freeze or not allow the piston to perform properly? I'll try the oil tomorrow. Stay tuned....