Re: Summerizing???
I'm with the others, what engine type do you have, what was done to winterize and what does the shop specifically say they do to summerize the engine? I have both an outboard and an I/O. The I/O I have professionally winterized, I'm in a freezing area, so they drain the engine and fill it with non-toxic anti-freeze, change the lower unit oil, remove the outdrive, greese it and reinstall it, check the belts, powersteering fluid, change the fuel filter, check the waterpump and fog the engine. Springtime I connect the batteries, hookup a water source and start the engine. After the engine clears of fog, I change the spark plugs.
Outboard: winterized, change the gear oil, check for worn wires and fog it. Springtime, I start the engine and after the fog has cleared, pull the plugs and either clean or change them.
I hope this info helps.
Successful Boating,
Art