Carbon in lower unit

[Barnbldr]

Is it normal to have carbon build-up in the lower unit? I had the motor running on the muffs and noticed leakage from one of the bolts connecting the lower unit, so I decided to pull it off and found somewhat heavy buildup on everything, as well as a bit of water/oil/gas/carbon muck leaking out. <br />Also, is it normal to have water in the lower?? I have some coming out of both the pee hole (good), and the exhaust (bad?).

 

[roscoe]

Re: Carbon in lower unit

This is normal, but a strong indicator of what your piston rings and head probably look like. It is time for you to perform some needed maintenance on that motor, DECARBING.<br /><br /> Click to learn about decarbing. <br /><br />90% of the cooling water does exit with the exhaust.<br /><br />The lower unit lube is inside a sealed portion of the lower unit. It should not be milky/grey or contain water. If the lube is grey, it is contaminated with water. Time to change it and find the leak, hopefully just the gaskets on the drain and vent screws.

 

[Osprey]

Re: Carbon in lower unit

Excess carbon or 2-stroke oil in lower unit exaust ports is often caused by a thermostat that is stuck open. The over cooling of the engine causes it to run rich at idle and low rpms.