1989 chev 74 litre 454 not pumping water

i just bought a 1989 chaparral

i just bought a 1989 chaparral sx2350. it has a 7.4 litre 454 chev engine with mercrusier bravo 1. before i bought it i got the guy to start it in the yard and it worked fine. then we took the boat home and accidentaly ran pretty warm water through it( through the garden hose). and then this morning we tried to start it and the alarm started going off (over heating alarm). we then replaced the impellor and it worked fine for the first 3 mins then the exhaust stoped spittinhg water out. and i don't know if this has anything thing to do with it but when the outdrive is up all the way then the exhaust bellows isn't long enought to reach the recieveing end ( near the to of the shaft). does anybody know what i need to replace?

The 1/2 exhaust is normal. Ba

The 1/2 exhaust is normal. Backflush all water lines leaving the impeller pump. Look for broken rubbber impeller pieces. You may need to replace the new impeller if it ran dry.

I'm having impeller issues

I'm having impeller issues also and was wondering How do you back flush the lines?

use a garden hose w/a straight

use a garden hose w/a straight nozzle and insert it on the opposite ends of the hoses.