instant engine overheating due to no water flow on mercruiser bravo 1 with 502 mag

[mtileman1]

Hello everyone,

Brand new to site, have a bit of experience in motors but not too much on boat motors etc.

I just took my boat out, started up everything seemed fine but after about 5 minute at idle started overheating at idle, found out no water circulating, no water out of exhaust.

Where would be the best area to start checking?

Impeller, thermostat?.........

[Don S]

The impeller is the FIRST thing you check on any overheat on a marine engine.
Those impellers should be changed every other year.

[mtileman1]

Thanks for the reply, as I said, not much experience in boats, any advice on where to start, i'm very mechanically inclined but need a bit of direction, any links to manuals you might be able to send me to?

Thanks

[Don S]

Just like cars, things change year by year. Does your engine have a year, better yet, a Merc Serial Number, since nothing is listed by year.

[mtileman1]

2000 502 mag mpi, bravo 1
drive serial #ol747991

[Fun Times]

For your engine, Your looking for mercruiser service manual part number 90-8613261, SERVICE MANUAL #23. Your engine parts are below.

http://www.mercruiserparts.com/Show_...Sea+Water+Pump

http://www.mercruiserparts.com/selec..._nbr=804807+99

[Don S]

Here is a link to the manual for that engine http://www.4shared.com/document/7EeC...Manual_23.html
Section 6 covers the cooling system. I would suggest pulling the complete raw water pump to replace the impeller, make sure you mark where the hoses go, they will go backwards and you will burn up a pump.
If it's the black composite housing, NEVER start the engine without water. They get damaged very easily.

[mtileman1]

Thank you so much,

I will keep you posted on how it's going.