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monkeyswrench

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Inlaw has a pontoon. Said toon has some cracks in one tube, so it almost sunk. It has a 90hp Merc 4stroke. It wouldn't start...clunked.
I looked at it yesterday, pulled plugs and wd40'd the cylinders...water in 3 and 4 :oops:
After some coaxing, I got it lit. It sounds sick, dead hole. So, my question is, do these things bend rods? Did water get somewhere else? Oil looked good, and it didn't look like the cowling went under. Fixing the cracks in the too tube I can handle...the motor may beyond my ability though. Any input or ideas are appreciated, thank you.
 

Ragged Edge

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Have you checked compression, done a leak down, spark check? If enough water got into the cowling that the electronics got wet they may need time to dry out or could be permanently f'd and you'll be chasing your tail. If you don't have spark on one hole give it some time to dry out and check again, no improvement take it to a Merc mechanic with the proper diagnostic equipment.
 

monkeyswrench

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Have you checked compression, done a leak down, spark check? If enough water got into the cowling that the electronics got wet they may need time to dry out or could be permanently f'd and you'll be chasing your tail. If you don't have spark on one hole give it some time to dry out and check again, no improvement take it to a Merc mechanic with the proper diagnostic equipment.
First thing I thought of was a compression check. I wasn't prepared for that, didn't even know the motor was an issue. I had only stopped by to look at the toon cracks. When I was talking to inlaw on the phone, he mentioned the motor wouldn't start. So, I tried what I knew, and had tools for. He's out there today, and I think he has a compression gauge in his garage...which I didn't have a key too.

Fun, fun...I'll keep you posted!
 

HydroSkreamin

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Yes, they can bend rods, but usually you would have to take the plugs out and spin it over to get the water out anyway.

Could rust a valve too.

Compression and leak down are great tools for diagnostics.

If you have a dial indicator that threads in the spark plug hole, you can thread it into each cylinder and they should be within a couple thousandths of an inch of each other. If you get one or two way low, you’ve got bent rods.

It should still start, though, unless the ring lands are broken.

Good luck and don’t overthink it.
 
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