Headache on a rebuild

[revlimiter776]

Repopped a 2.5 for a guy a month ago, one new slug 10 over , rest all new rings. Bad head was replaced, all new seals , bolts ect he sends me this picture toddy. I have not had a motor come back yet Definitely not for water intrusion. What do you think? Do you think they were sucking water in under the cowel? Fuel? Water in oil ?

[XstreamVking]

For month old plugs they have a lot of corrosion on the bodies themselves. looks like water intrusion. And the internals look to have been pumping a lot of water also. Weird all of them got wet. Exhaust divider could be the culprit for that.

[LakeFever]

Head gaskets? It’s very weird that it’s ALL plugs imo. This doesn’t seem right because both heads would have problems on every hole. The rear cover? I can’t see how the exhaust divider causes issues with water in the cylinders that is something I’d like to hear more about.

That also could be ethanol laced fuels that soaked up a ton of water. I’ve seen gallons soaked into some tanks before. Imagine the scenario where you have water fouled fuel, you try to start the boat and it doesn’t run right or at all. You crank and crank and crank then throw in the towel and give up until next weekend. Meanwhile water gets in the cylinders and rusts everything to rat crap. Then next weekend it’s try again and so on then someone finally decides to pull a plug and those plugs are what you see

[XstreamVking]

Divider gasket gets compromised, motor still runs. You trim the engine up to trailer home. Water runs into cyl's thru exhaust ports? Just a guess..... Not many ways to get all the plugs wet.

[LakeFever]

Makes sense. Agree there really isn’t many paths to get in there. The fact that the plugs are so rusty makes me think fuel because cranking it with water would wash over them every crank. If it was just sitting water it would most likely have a line in the cyl where the water sat and caused the rust. Being all over the plugs speaks to cranking with water in fuel because again if it was sitting water and the fuel was clean the plugs would be covered in oily fuel on top of the rust from sitting. They don’t look as if they have really seen much fuel just water and squished all over them. I’m guessing it’s an efi motor. That’s my guess anyways it’s never easy to guess without taking a look which would only take a few mins to find out for sure

[OnPad]

Looks like it sunk. Big wake/ waves, low engine height?

[ChrisCarsonMarine]

I've seen similar conditions from a leak in the flush hose on the botton of the exhaust plate bringing water into the pan and airbox,also the speedometer tube can if in the right position squirt water into the airbox.I would look for something like that,as that motor has been getting a small dose of water while running over a preiod of time in all the cylinders,Chris

[pcrussell50]

I've seen similar conditions from a leak in the flush hose on the botton of the exhaust plate bringing water into the pan and airbox,also the speedometer tube can if in the right position squirt water into the airbox.I would look for something like that,as that motor has been getting a small dose of water while running over a preiod of time in all the cylinders,Chris

Excuse the ignorance, but what is the path from the speedometer tube, to the air box on a Merc V6?

-Peter

[XstreamVking]

I have also had the poppet blow a gasket and fill the cowling up pretty good. Drains were clogged. Forgot about it since it happened 20 +yrs ago. Saw water coming out of the cable inlets on the cowl when I trimmed up. Didn't overrun the airbox and get in motor.

[Carter Powell]

Early Merc V-6 motor had a small hole in the front of the lower unit that was the pick-up for the speedometer, that was fed by a plastic tube that ran up in front of the powerhead before it was sent to the speedometer. If the connection in front of the powerhead came loose it would spray water everywhere in front of the powerhead.

Carter Powell

[WaterZebra]

Repopped a 2.5 for a guy a month ago, one new slug 10 over , rest all new rings. Bad head was replaced, all new seals , bolts ect he sends me this picture toddy. I have not had a motor come back yet Definitely not for water intrusion. What do you think? Do you think they were sucking water in under the cowel? Fuel? Water in oil ?

The crud on the electrodes almost looks rusty (water). Try a new set of plugs, run for a few minutes and see what accumulates? The divider is not the problem (side to side leakage). Water is getting in from somewhere. The crud seems to be dried and the amount is a lot for just one month of operation.

[ChrisCarsonMarine]

Excuse the ignorance, but what is the path from the speedometer tube, to the air box on a Merc V6?

-Peter

The factory pitot tube for the speedometer is located on the leading edge of the gearcase,feeds up to a plastic fitting screwed into the top of the gearcase by the shift shaft.A1/16 plastic tube fits into it and travels up the swivel tube along with the upper shiftshaft,and inters the cowling in front of the block.At 0 speed it does nothing,but the faster you go the more it squirts,sometimes in the vicinity of the air box/intake.I'e had 2 powerheads go this way,and you wont see the water till you're moving,Chris

[pcrussell50]

Ah. Got it. The tubing would have to be split or broken open in the vicinity of the air box, if I am understanding correctly.

-Peter

[ChrisCarsonMarine]

Ah. Got it. The tubing would have to be split or broken open in the vicinity of the air box, if I am understanding correctly.

-Peter

Or just not hooked up...

[David - WI]

The factory pitot tube for the speedometer is located on the leading edge of the gearcase,feeds up to a plastic fitting screwed into the top of the gearcase by the shift shaft.A1/16 plastic tube fits into it and travels up the swivel tube along with the upper shiftshaft,and inters the cowling in front of the block.At 0 speed it does nothing,but the faster you go the more it squirts,sometimes in the vicinity of the air box/intake.I'e had 2 powerheads go this way,and you wont see the water till you're moving,Chris

When that tube comes off the speedometer at 90mph it will just about fill the boat with water before you can stop!