Water pump on a merc 500 50 hp

[78 280zcar]

OK, I have some problems with my water pump on my merc 500 50hp. I have just changed the water pump impeller and the whole housing because everything was really shot, and when I hook up a water flusher to the engine it doesnt pump water out of the tattle tale hole, someone told me that the line could be plugged from pieces of the impeller going into the water tube and sure enough it was so I changed the water outlet that goes to the powerhead and to the tattle tale hole and it still doesnt come out I tried putting a hose to the line that goes to the tattle tale hole and water comes out but not out of the water tube that goes to the pump, is there any way somebody can point me in the right direction. Thanks

 

[Kenny Bush]

Re: Water pump on a merc 500 50 hp

Take an air hose and blast into the little hole. It will also take a minute for the thermostats to open up an let water come out of the tell tail.

 

[78 280zcar]

Re: Water pump on a merc 500 50 hp

is there a thermostat on this model I think its a 1972 but i am not sure because there is no serial #,

 

[Chinewalker]

Re: Water pump on a merc 500 50 hp

No t-stat on a Merc 500. Go the compressed air route to determine that all the passages are freed up of crud, mud-dabber nests, sand, etc... You can go up through the water intake, and back through the pisser - either way you should be able to figure out if things are open or not...<br />- Scott

 

[tmcalavy]

Re: Water pump on a merc 500 50 hp

make sure its getting enough water (pressure) when on the muffs and don count on a strong stream running at idle. I have the same ouitboard, only its a 73, and it barely pees out the telltale at idle. Bump the rpms a little and away it goes.

 

[andrewkafp]

Re: Water pump on a merc 500 50 hp

Agreed on the pressure.<br />At idle, my 81 50 just trickles out. At 3000 RPM it runs at about 4-5lbs and close to WOT is around 7lbs and really squirting.