hello, I have a question for the y-block experts. I have been unable to find pressure rating specs for my 239 y. it currently has a 7lb. cap on it. the reason I am not sure this is correct is I also have a 55 merc w/ a 56 312 y in it and it has a 13lb cap? did the pressures of the y-blocks vary over the years? when I run the 239 and it gets hot it does not seem to build pressure, you can remove the cap as if it was cold. I was always told the right lb., cap is critical to the cooling system. any thoughts or opinions? thank you to all that have responded in the past, your input is very helpful, doug.