Bicycle pump affixed to my MerCruiser inboards

[hynespa]

I have two MerCruiser inboard engines on my Sea Ray 420 Sundancer.
Each of the engines has attached to it a small blue bicycle pump and on each engine there are air valves similar to what you would see on a bicycle or automotive tire.

It’s always been a mystery to me what the valves do and if or when I should be checking the air pressure on the valves as well as whether I should be using the pumps to inflate to a certain psi.

Would appreciate anybody’s insight into helping me solve this mystery?

 

[Woody]

 

[hynespa]

Thanks @Woody. My boat under a previous owner was up in Minnesota- so I’m sure the PO used those pumps to winterize. I’ve always owned the boat in Southern California so I have never had to winterize.