Riser Gasket question (Mercruiser)
 

I have a 1989 350 mercruiser with an alpha drive and I am having cooling problems. I jsut put in new riser gaskets and have a question. Why lift to right on the gaskets are they open and front to back are there only pin holes? is this to limit flow? Can I open them up to see if I get better flow out of the motor and through the exhaust? I just want to see if I will hurt anything before I go and do this... Thanks guys

I'm not quit sure why the pin holes, but they have been that way for years and things cool fine, I would look else where for my problems, waterpump, themostat, blockage in sys. has there been any recent problems?