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How do I ensure there is no water in this boat motor?

Google has failed me OPPO. Does anyone have experience with a newer Yamaha 40 HP outboard Jet? I need to make sure there is no water in the Cooling system since we store it outside and it will be 7 deg F tomorrow. The boat is currently taking up garage space from my Subaru and Mazda.

What I have done: disconnected the flush hose and blew it out with compressed air, about 1 oz of water came out that was it.


The flush hose is that 1/4" hose screwed onto the outside of the engine. You can connect it to a garden hose to flush the cooling system after running in dirty water.

What I was also thinking,

1. take off the thermostat housing and blow it out, making sure there isn’t any water in the top of the engine. But this motor may be self draining, I just don’t want to be responsible for ruining a very nice outboard.

The thermostat housing is at the top of the engine with 2x 10 mm bolts holding it in, should be easy to remove.


2. Force flush through the flush hose some anti-freeze (not my preference because it will be messy and some of that will go into the next river we put the boat into.)

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