4.3 V6 Rebuild Not running right

[mattmullen]

Hi Iboats,
I'm stumped and I need some help. I bought a basket case 1991 Sea Ray last fall.
Over the winter I worked on rebuilding the 4.3 v6 that blew up because of lean burn detonation.
It fires right up and runs on my home made stand but cylinder #3 is not firing, if I pull the plug wire at a variety of engine speeds there is no change. When you hit the throttle and as it comes back down it idles very poorly for 10-15 seconds and then evens back out. I have also noticed some condensation on the insides of the valve covers and the bottom of the intake manifold (I am not sure how much of this is normal I am new to marine engines). If I pull the risers right after running I see some droplets of water on the cylinder #3 side none on the other bank of cylinders. When I pull the spark plugs on that side #1 looks textbook perfect burn #3 and #5 look rich (all black and sooty). #2, #4 and #6 look textbook as well.

I have done the following
Pressure tested cooling system-It leaked down slowly from 15psi to 5 in a weeks time.
Leak down test-good on all cylinders
Compression test- good all cylinders at 150 psi +/- less than 5 psi
Checked spark- good blue spark on #3
Adjusted the valves meticulously

New Parts in rebuild
Pistons-.030 over Sealed Power
New Roller Lifters
Rebuilt Heads
Edlebrock 1409 Marine Carb
Edelbrock Performer Manifold
Delco Voyager EST Ignition/Distributor
Aluminum HGE Exhaust Manifolds and Risers

Heres a video of it running today.
Any ideas?

 

[alldodge]

I think you sucking water back into the motor. What cam is in the motor?

 

[alldodge]

I'm going to take that back, you have an intake water jacket leak


That's water isn't it? What does your oil look like?

 

[mattmullen]

Yup its water. The oil looks good I get some foamy condensation on the back of the valve covers and on the bottom of the intake and on the distributor shaft. I thought the water was coming from the engine running poorly and getting pulled back in the exhaust, thats why I extended the riser with the pipe you see in the video. Also its the stock mercruiser cam. It was in perfect shape.

 

[alldodge]

If the water was being pulled in thru the exhaust then it would be in the piston area, but not the valve cover or distributer shaft. Your leaking water into the block

 

[mattmullen]

Hi AllDodge,
Thanks for the feedback, but would a water leak cause cylinder #3 to not fire?

 

[alldodge]

If water is coming in and mixing with any cylinder, that cylinder will not fire. The question is; where is the water coming from, not which cylinder is or is not firing. There should be no water inside the engine block

 

[flipbro]

You got a leaky riser/elbow gasket is my bet.

 

[mattmullen]

If I had enough water getting in to cause a misfire wouldn't I see it in the exhaust? Whats the best way to test for a leaky riser gasket?

 

[alldodge]

If I had enough water getting in to cause a misfire wouldn't I see it in the exhaust?

Depends on how much is going in.

I still don't see how you can have water creating foam in the valve cover and it not show up in the oil

 

[turbocorrado]

Depends on how much is going in.

I still don't see how you can have water creating foam in the valve cover and it not show up in the oil

when i bought my boat i checked the dipstick and it looked fine, then i sucked the oil out and got 5 quarts of oil and 3 quarts of water. im assuming if he drains the oil he will see some water

 

[Rick Stephens]

Agree with turbo. If you don't suck or drain some oil off the bottom of the pan you won't know if there is any water in there.

 

[mattmullen]

No Title

Pulled the valve covers and the riser to see what might be going on. I drained all of the oil to take a look at its condition and took a picture of its condition, FYI its Royal Purple break In oil. Please take a moment to look at the photos and see if anybody has any ideas. Thanks in advance. -Matt

 

[alldodge]

I'm still thinking you have water coming in via the intake manifold, and here is my reasoning.

Synthetic oil will not turn into a milk shake like conventional oil. You could take a jar of royal purple and add some water. Shake it up then watch as the water sinks to the bottom. Cylinder 3 was found with water in it and moisture is found under the valve cover. I don't think it's a lot of water

If you drained the oil out the drain plug look for some water in the bottom of the pan. If it was sucked out then you may not find any. Don't think there is a lot of water going in, just enough right now to cause issues. Think its the intake because the moisture is getting into the block not just the cylinder.

If this was regular oil the milk shake should show up after it has run long enough to reach around 0.1% emulsion.

As for the plugs getting black, I would say your running rich

 

[mattmullen]

Hi AllDodge
The engine oil is Royal Purple break in oil which is non synthetic. I never found water in cylinder #3 only droplets in the exhaust manifold after shutdown. I drained all of the oil out of the engine and I watched as it flowed into the funnel. I never saw any water separate of the oil. When I pressure tested the cooling system two weeks ago I filled it with a water / uv dye mixture. After leaving it sitting under pressure for a week I released the pressure drained the dye and pulled the intake and oil pan and inspected every square inch of the engine with a uv flashlight looking for traces of the dye... Nothing. Needless to say I am frustrated. Please keep the feedback coming I am hoping somebody can hit on something I haven't tried or thought of yet.