I've recently purchased a Cal 2-27 and am going over everything to learn and fix things. Since I've only sailed small boats I really have a lot to learn about all these...things. The item below is located just above my engine gauges in the cockpit and usually has a screw cap over it. Here's the first of many questions to come. What is this?
Thanks Jared

mysteryguage by picndicular, on Flickr
Thanks Jared

mysteryguage by picndicular, on Flickr

