As the title states. The #5 plug is showing up very clean. At first I thought the cylinder wasn't firing, so I replaced the plug wires and verified the plug was getting spark, which it is. The motor shows no syptoms that it's not hitting on this cylinder... RPM's are good, no popping, fueling of oil, Compression test was fine too.

Could it be reversion on that cylinder? The original manifolds/risers had a leak, and I just replaced them with GLM cast manifolds and 4" risers. The oil looks great too, not milky at all.

Any ideas gentlemen? I'm at a loss.

TIA... Brandon

thats water ..... it cleans the plug ....tap the plug in the palm of your hand and see if you get a drop ....

#5 and #6 are are known to have problems. I just finished up with a problem like this and what happens is the exhaust port corrodes on these 2 holes. A leak down test may determine this if the exhaust or intake valve is not seating properly due to corrosion. For example, my #5 was 160 psi compression BUT leakage was 35%. All the other cylinders read 160-175 compression with an average leakage of 6%.
Another test you can do is remove the water supply line from transom (bravo) and fill with water. Remove the water discharge lines to the exhaust and plug them with a pvc plug. Adapt a fitting for your radiator type pressure tester & pump it up.

I had a borrowed a tool that was the cats ass. It was a viewer that I stuck into the cylinder thru the spark plug hole and noticed the corroded exhaust valve. Needless to say the exhaust port had a pin hole from corrosion in the port that was allowing raw water to do the damage.

After inspecting the spark plug the thought by a couple of guys at the marina is that I've got a dead injector on cylinder #5. They seem to think the plug has never even fired. No signs of gas or water on the plug either. If I get out of work in time today, I'm going to toss a stethescope on the injectors. What do you guys think? Injectors pretty easy to change?

Thanks again !

Unplug that cylinders plug wire from the distributor while it is running to see if the cylinder is firing, you'll hear a change.

Cheers,
Pismo