78 Merc 900 Water trickles out at idle

[kfrei]

When engine idling water seems to come out erratically and under low pressure (I think) I can stop the waterflow by just touching the hole with my pinky. At higher idle water comes out steady but can still stop flow with finger. I was thinking of changing the water pump. <br /><br />If I change the waterpump should the thermostat also be changed if it has never been before?

 

[Kenny Bush]

Re: 78 Merc 900 Water trickles out at idle

What you are seeing is normal. The tell-tale is allways low, and even at a cold start it takes a while to get a trickle coming out.......You have to wait until the thermostats open up.. Many people use a water pressure guage instead of a temperature guage. Your guage will read about 3 to 5 psi at idle, and 12 to 15 at higher RPMs.

 

[The Marine Doctor]

Re: 78 Merc 900 Water trickles out at idle

The water at no time should stop comming out of the telltail. <br /><br />If the telltail is obstructed in anyway, it will be low on pressure. Blow compressed air into the telltail hole and hose.<br /><br />If the water does not pickup pressure it might be time to check the waterpump for wear.<br /><br />TMD

 

[greasemonkeyozi]

Re: 78 Merc 900 Water trickles out at idle

Dont ever run your motor if water is not coming out that "pee hole," or tail tell. If you havnt changed out your water pump this year, nows a good time to do it. These things need to be changed out at least once a year, others will tell you once every season.