Mercury 40 HP jet

[techforu@alltel.net]

I surely hope someone can help me. I have a 1998 Mercury 40/30 jet it was not peeing correctly. I put new impeller in and it peed great. On the river it got hot and alarm went off but was still peeing. Put new thermostat in and still got hot. It quit while I was on river but still peeing but water was so hot coming out of it, it would burn your hand. Checked the new thermostat and the plastic housing was completely melted and thermostat ruined. No water is getting up to the thermostat, the only pump is the impeller. How can I get the water to circulate thru the thermostat. Forced water and air thru thermostat housing thinking there was a blockage. No blockage. Anybody ever have this problem? Any help would be appreciated.

 

[WillyBWright]

Re: Mercury 40 HP jet

There's a blockage alright. Or more precisely a build-up of sediment in the block. There still might be a path for some water to circulate through, but sand is preventing the water from reaching all the surfaces it needs to cool. Take the jet pump off and backflush through the thermostat hole with a garden hose, not air. I'll bet you get a pile of sand under the motor as it washes out. Then put the hose on the pipe underneath to forward flush out the thermostat hole. Go back and forth back flushing and forward flushing until no more sand. You still won't get it all out, but the vast majority.

 

[techforu@alltel.net]

Re: Mercury 40 HP jet

I flushed with water in the therm hole and underneath still not getting water up to the thermostat, any other ideas? Thanks for the help

 

[techforu@alltel.net]

Re: Mercury 40 HP jet

When I flush from bottom I only get water out the pee hole not the therm hole. Am I doing something wrong?

 

[techforu@alltel.net]

Re: Mercury 40 HP jet

Does any one know if I can run this engine without the thermostat in???

 

[WillyBWright]

Re: Mercury 40 HP jet

If the sand is packed in there hard enough, flushing might not work. Adding vibration might. Maybe do it while it's running. Otherwise disassembly may be necessary. Or the problem is something else.

 

[techforu@alltel.net]

Re: Mercury 40 HP jet

Hey Willy thanks a lot, that worked great it took a while. The hose didn't seem to work so I used my pressure washer that worked great. I left the thermostat out because the plastic housing was melted. I gues it won't hurt anything just won't get up to temp. Thanks again