I have been working on my Ericson 27 that I bought in February in Annapolis. I have gotten down to the last few items on my punch list in order to sail her two days back to the southern section on the Bay in Virginia (near Deltaville). The A-4 impeller replacement is now on the list. How hard is this to do? Boat hasn't been in the water in 3 years! The motor starts and idles, but can't really run the motor to see true condition until I get it in the water on Friday to sea trial. tips? Thoughts?