Bubbling fluid around spark plugs under load
 

I know, this sounds strange, but I don't know why this is happening.
We have been trying to solve another issue and this one popped up.

They may be related, so I will tell you about both of them.

Our A4 starts fine and runs for a while (30 minutes at 1500-2000RPM) and then dies.
If we wait for 15 minutes, it will start and fun fine for another 5 minutes, repeat as long as you want.

Last year we had the same problem, but we discovered that if you kept the RPMs below 1200. it would run as long as we needed it (about 1 hour)

Over the winter I rebuilt the carb and the mechanical fuel pump.
Last year I replaced the fuel filter. To take it off the list of possibilities, I will replace it again tomorrow
Any Ideas?

While we were running at 2000RPMs yesterday, I opened the engine hatch to look at the engine and 2 of the "spark plug wells" were full of bubbling fluid (could be boiling water or maybe cooling water with exhaust gasses escaping out of ?
When the engine was running at 1500RPMs or less the "spark plug wells" returned to looking dry.
Background; Great lake 1965 boat, freshwater cooling.
Any ideas whats going on.? Thanks for your advise.

Alternator bracket
 

Hey China Sea - very likely you have a head leak under the alternator bracket (aka lifting eye). Is the water pooling on the #3 and #4 spark plugs?

Thanks Marty
yes # 3 and 4.
How is the water getting into the spark plug well?
is that boiling water (overheating) or is that escaping gasses (compression) gasses.?
is this a cracked head or a leaky gasket?

China, likely the water is coming up through the threads in the stud this is the easy one. The other is a crack in the head from improper torque on the bracket.

Dave Neptune :cool:

Dave, Thanks for the input.
Does that mean either the studs need to be tightened, or a gasket problem, or in option 2, they were over tightened and cracked the head.?

How is the water getting over to the spark plug wells.? Through the gasket? or running over the top. I did not see any water running on the top.

Ill look again when I am out to the boat this friday

Thanks again
Dan

Dan, if it is a stud leaking it is an easy fix as the head can be left in place. It is basically just resealing the stud and retorquing.

In the above the water runs over the top of the head~~not uncommon.

If the head is cracked it can sometimes be fixed via welding and a resurfacing of the head. Or you may just find one from a member with an extra one and there is always a brand new MMI head :D.

Dave Neptune :cool:

Your first issue - running for 30 minutes and then dying, is a classic example of a coil going bad. When they get hot, then don't work. Running at lower RPMs keeps the coil cooler, and also letting it sit for 15 minutes cools it off. If you have electronic ignition, which I recommend you get if you don't already have it, then you need a coil from Moyer Marine. Don't just use an automotive ignition coil because they might not have the correct resistance.

Dave and Marty, you called it. perfectly
There appears to be a crack in the head (bummer for me) between the #2 and #3 spark plug. When the engine is unloaded and up to 2500 RPMs little droplets start to form along it.

Is there any danger in running the engine this way this summer and replacing the head in the fall.? Or am I destroying more as I run it.

Hi Zellerj
That sounds like that could be it. Ill need to look and see if I get spark from it next time it dies on me this Friday.

Maybe the fuel tank vent is blocked or partially blocked. To test try running with the fuel fill cap ajar and see if the shutdowns go away.

TRUE GRIT

Thanks for that thought. I was along those lines earlier. As a fuel solution possibility I loosened the cap, rebuilt the carb and fuel pump and took out the additional fuel filter I had installed. Still clonked out after 30 minutes. I think I will put the filter back in, but above the pump this time to keep the screen on the pump from getting clogged.

Tomorrow, it the leftover of the hurricane moves out, I will install a replacement ignition coil and try that out on Friday. Thank you to everyone for ideas.
Dan

(Is there any danger in running the engine this way this summer and replacing the head in the fall.? Or am I destroying more as I run it.)

You would be taking a big gamble running with a cracked head. It could let go at any time especially if it overheats. I wouldn't even think of leaving the dock unless I was confident the problem was fixed. My advice, find yourself a replacement head and save yourself a lot of time and grief.

Coil is a good place to start and I would replace the condenser. I had the same running/stopping/coolingstarting cycle a few years back and was advised to change the condenser after a week of doing everything else. Problem solved.

Mine was doing that. Turns out that my new tstat housing wasnt tightened enough. Lol

If you have a thermostat, not seating it properly in the housing groove can result in leakage too.