89' Mercury 135 Overheats at 2000rpm

[Mack43432]

G'day from Geelong, Australia

Went for a dive in my mates boat the other week, got the leg stuck in sand and sucked up some mud. Was overheating on the way home over 2000rpm.
Yesterday flushed the cooling system, pulled the puffer valve out and cleaned it and thermostats. Got alot of sand out, seemed to be pumping good at home.

Tested it out today and warning lamp comes on at 2000rpm.

Any ideas or something I could of overlooked ?

Thanks in advance.

Mack43432

 

[CharlieB]

Re: 89' Mercury 135 Overheats at 2000rpm

Did you replace the impeller and inspect the SS cup and plate for scoring from the sand?

Running on the hose at home can be misleading, hose pressure can 'assist' the pump and look like it is pumping water just fine. Actually the scored tips of the vanes fail to maintain water pressure.

Installation of a water pressure is a great tool to constantly monitor cooling system status.