Merc 150 XR4 weak water pump?

[Steven R Langston]

Had the water pump replaced on my 89 Merc 150 XR4 last year. I've noticed recently that the 'pee stream' seems weak until I am up to about 1500 RPM and moving at low speed - then I finally get a 'stream'....Is this normal? I have to admit that I've never really paid any attention to this till my 'overtemp' alarm sounded while idling prior to a tournament blastoff last weekend (after idling about 10 mins.) After shutting down for a few minutes to cool off, I started it - ran fine all day - no overtemp probs......Time to replace the pump?

 

[12Footer]

Re: Merc 150 XR4 weak water pump?

Hi, Stevens, and welcome to iboats. If this is something 'just recently' happening, yes, it's time for a new impeller. It could also be old pieces of the last impeller have found thier way into a point in the water jacket, became lodged, and are blocking or restricting the water flow. The most likely place for this to occur, are at the thermostat and poppet valves. But impellers only last a couple seasons under normal operation. But if you run in salt or silty water often, and do an inordinate amount of idling, the impeller would wear-out much quicker. Also, it may be time for a new thermostat. After changing-out the impeller, remove the thermostat,run the engine for a few minutes to flush the block out, then replace it.

 

[Steven R Langston]

Re: Merc 150 XR4 weak water pump?

Thx "12Footer" for the info. I'll pick up a new impeller kit and t'stat next weekend.........you and others make this a great web-site...