150 Merc impeller change

[fish-N]

I have a 1988 mercury I just changed impeller and gaskets. When I started motor with rabbit ear flusher it took about two minutes for hard stream of water, it would then go to a spit for about 20 seconds, then it would shoot hard stream for about 20 seconds. this pattern did not change. I ran motor for about 4 minutes is this normal?

 

[Rangerbilt]

Re: 150 Merc impeller change

I have a 1983 150 Blackmax that would do the same thing. I have replaced the thermostats and impeller but it does the same thing. When I'm at the lake during idle, the water coming out of the pee hole is hot to touch but not scorching hot. When at WOT I have continuous water coming out of the pee-hole. It's been like this for about three years now.. I've been replacing the impeller every year for the last three years as a precaution.

 

[andy6374]

Re: 150 Merc impeller change

What you are seeing is the thermostat opening and closing.

 

[andy6374]

Re: 150 Merc impeller change

By the way it's recommended that the t-stats and poppet valve assembly is replaced every 2 years as well.

 

[fish-N]

Re: 150 Merc impeller change

thanks for the information.what does a poppet valve do and does it cost a lot to replace? should I be worried that the t-stat is not working right?

 

[ladano]

Re: 150 Merc impeller change

my 115 does the same thing, I was worried. Do you really need to run a thermostat in the south? the water temp rarely drops in the lower '50s.

 

[andy6374]

Re: 150 Merc impeller change

If your t-stat is stuck closed you'll overheat, if stuck open you'll run cold. So they need to be functioning properly.<br /><br />The poppet valve assembly regulates the pressure withing the cooling system. If the poppet is stuck closed it will cause overheating at higher RPM's, if it is stuck open it will cause overheating at idle RPM's.