Last run of the year and the water pump went out. Do I have to buy this from Mercury or can I cross it over and get it cheaper from a autoparts store? The part # for the Mercury is 8504541. Thanks, Mike

The difference is the marine circulation pump has a stainless impellor, shaft and rear plate. An auto one is just stamped steel and wont last as long. Plus if you buy one from Merc you get a year warranty with it so save the receipt.

Have you pulled the pump apart yet to see if you just need parts for the pump?

No I have not. I was just going to replace the entire pump.

If you are going to replace the pump do it right. it is better to spend the money up front the spend it later cause you sea pump went out witch can cause alot more money. Are you looking to just repalce the pump with a stanard pump or are you looking to upgrade to a performance pump?

Why not just change it out for a crossover and be done with it for good?

Crossover might not be that easy on a 500EFI.Better if it could be done though.

If you are running a closed system, why wouldn't an automotive pump work? You are running a coolant with rust inhibitors in it just like your car, and those pumps last a long time.
Ken