pump starts strong then slows to a drip

[thechopfather]

Recently put a used leg on a 1979 mercury 9.8 model 110.Has a good stong stream of water from pump when first started but the water slows and stops squirting after about 30 seconds to 1 minute.If I stop the engine and start it again it will pump for another few seconds to a minute and then slows till it stops.the motor runs fine during this and never quits or hicups or anything.The power head has been used for a couple of years with the previous leg.No problems till it just quit pumping. [/LIST]

 

[Laddies]

Re: pump starts strong then slows to a drip

Sounds like old impeller blades either in the w/pump pick up or in the engine cooling system.Did up pull the water lie to the telltale

 

[thechopfather]

Re: pump starts strong then slows to a drip

hi,<br />I'm not sure I get the last part of what your saying.the impeller looked Ok.No cracks or broken fins.I Will change it though.Thanks.

 

[Laddies]

Re: pump starts strong then slows to a drip

Over the years a impeller will go bad and the person that replaces it don't take the time to find the peices, when the engine is started the water will carry them to a resticed point in the cooling system and block it, when shut down there is no pressure and the blockage opens till the water pressure closes it again

 

[thechopfather]

Re: pump starts strong then slows to a drip

Yeah that makes perfect sense!Any ideas how to get those obstructions out?Tried forcing air back through from the outlet.Reassembled and still the same result.<br />Thanks

 

[joblo33]

Re: pump starts strong then slows to a drip

Another thought: <br />When it's slowed down to a drip is there exhaust shooting out the pisser? It would feel like compressed air. If there's quite a bit of it I'd change the exhaust gaskets. These motors are famous for bad exhaust gaskets. When the gasket has failed the exhaust leaks into the cooling system as the exhaust pressure builds. This causes it to **** for a couple seconds then just spray exhaust and a little water.<br />Eric

 

[DHPMARINE]

Re: pump starts strong then slows to a drip

I don't have a real complete answer but a little info :<br /><br />Sounds to me like your engine has a thermostat in it.The parts book shows with and without thermostat.So they made 2 versions.<br /><br />Engines without thermostats circulate water contantly as they run.Constant telltale.<br /><br />Engines with thermostats cycle water as they run.<br />Start it,reach a temp and water comes out the telltale.Motor cools down,telltale stops.Motor warms up,telltale again.<br /><br />I'll bet you have a thermostat.<br /><br />DHP

 

[thechopfather]

Re: pump starts strong then slows to a drip

Eric described it exactly.quite a bit of exhaust coming out of the pisser hole not much water.

 

[timmathis]

Re: pump starts strong then slows to a drip

I think Eric has the ticket.