# Intermittent peeing Mercury 15 hp 2 stroke



## jrasband (Jul 12, 2010)

Just picked up a like new 1995 mercury 15 hp 2 stroke and the stream out of the tell-tale alternates between a trickle and strong flow. I'm pretty sure this is the thermostat keeping the motor at optimum running temperature but even after a test run at full throttle it still cycling between a trickle and strong flow. The block didn't feel hot and I was running in cold water, so it might just be the engine trying to stay warm.

I'm taking this boat to the Everglades in a few weeks and making some long runs so yes I am slightly paranoid 

Is this normal or should I be worried about the thermostat/impeller?


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## Smackdaddy53 (Dec 31, 2012)

Thermostats, water pumps and maintenance are cheap compared to ruining a powerhead. I would replace them and then run it.


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## Jim Lenfest (Jul 20, 2016)

Smackdaddy53 said:


> Thermostats, water pumps and maintenance are cheap compared to ruining a powerhead. I would replace them and then run it.


I would concur, change the impeller and the thermostat. Since you are in warmer waters, you might remove the thermostat altogether. We do it here in Maine, but they do take a few minutes to warm up in our colder waters.


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## Smackdaddy53 (Dec 31, 2012)

Jim Lenfest said:


> I would concur, change the impeller and the thermostat. Since you are in warmer waters, you might remove the thermostat altogether. We do it here in Maine, but they do take a few minutes to warm up in our colder waters.


I don't recommend removing the thermostat because it's job is to allow the water to keep the head at operating temperature. There is such a thing as a motor running too cool and that is just as bad as running an outboard WOT as soon as you start it and have not allowed the head to warm up and that causes cylinder wall scoring and in turn powerhead damage.


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## Jim Lenfest (Jul 20, 2016)

True that it, the thermostat, has a function, to keep the temp in a particular range, but they often clog, freeze closed from corrosion, etc in sea water doing more damage from over heating than would ever occur from running cool. The dealer here has removed hundreds of them in local motors that get used daily year in and year out. Furthermore, none of the older motors ever had a thermostat. The water temp range in this area is from 28 to 60 and they run fine, just take longer to warm up. Me personally, I left mine in, and simply change it occasionally, but many around here would never consider maintenance. Therefore I would say that if you don't intend to do anything other than run the motor till it dies, it might be best to remove it.


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## Smackdaddy53 (Dec 31, 2012)

Jim Lenfest said:


> True that it, the thermostat, has a function, to keep the temp in a particular range, but they often clog, freeze closed from corrosion, etc in sea water doing more damage from over heating than would ever occur from running cool. The dealer here has removed hundreds of them in local motors that get used daily year in and year out. Furthermore, none of the older motors ever had a thermostat. The water temp range in this area is from 28 to 60 and they run fine, just take longer to warm up. Me personally, I left mine in, and simply change it occasionally, but many around here would never consider maintenance. Therefore I would say that if you don't intend to do anything other than run the motor till it dies, it might be best to remove it.


My guide buddy flushes his outboards religiously with Salt Terminator after every trip and at each servicing it looks new inside the water jackets and thermostat is clean as new.


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## Jim Lenfest (Jul 20, 2016)

Smackdaddy53 said:


> My guide buddy flushes his outboards religiously with Salt Terminator after every trip and at each servicing it looks new inside the water jackets and thermostat is clean as new.


I agree, it would. But we never flush ours, we just run em till they die, then buy another one. Many guys buy a motor, put it on their skiff, and leave it in the water year round, spring, summer, fall, winter, year in and year out. I do bring mine home daily, I think briefly about flushing it, but that is as far as it gets, lol. I like the used fresh water motors as they last as long as a new one in this environment, but many friends prefer brand new every couple of years because they simply want it to run with no maintenance every day. When you work 80-100 hours a week, you don't want to waste an hour a day flushing out a motor. Anyone that has the time to flush his motor every day, lives in a different world than we do here. Let's look at it from a dollar standpoint. Let us say that if you simply worked that hour and made an extra $50. You use your motor say 300 days a year, allowing 60 days as storm days or religious days. That is $15,000 a year. A non flushed motor will still run 5-15 years. That is why the guys just simply throw the motor away and just go get a new one. Me, I don't make as much, and I am of a conservative nature, so I buy used fresh water motors.


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