Cooling flush port

[yankee]

I just found that my 99 Mercury 150xl has a flush port right beside the pee-port.  Can anyone shed some light on how to use this port?  Can I have the engine running during this flush or does the engine stay off? Also do I need any type of fitting to fit this port to use a garden hose?

[Juan]

It flushes the engine block. DO NOT run the engine when using just that port because the impeller would be turning without water and will damage the impeller. Should connect with a standard garden hose.

[yankee]

Thanks Juan. I appreciate your knowledge.

[Juan]

Glad to help.. Now let me elaborate a bit: Flush ports flush the engine block only and if you've run the motor in fresh water that was dirty or muddy, using a flush port should probably be good enough but won't remove dirt, sand or salt from the lower unit or water pump. If there's a flush port on an outboard that supplies water to the lower unit, I've never seen or heard of it (and the impeller turns when the engine is running and needs to be lubricated with water) but that doesn't mean it doesn't exist. You could probably start and run the motor for a few seconds without any damage to the water pump's impeller but I wouldn't chance it. I'll use the flush port when I can't put the lower unit in clean water or I don't have a set of flush muffs and after running in dirty or salt water and since the engine doesn't have to be running when using a flush port, I sometimes keep a garden hose connected and running for a couple of hours after I've properly flushed the engine in a tank of water. I'm sure that's considered overkill.
imo
GOOD: flush with flush ports
BETTER: flush with muffs
BEST flush with lower unit in a tank of clean water.

[fraydknot]

Great advice!!!