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2000 Mercury 125 hp 2 stroke Overheating could it be more than thermostat and water pump?

J

Jhanratt

Regular Contributor
I had a really bad day at the lake. My trolling motor went down first (broken intake valve spring) then my main power went down while trying to get home.

It started with the siren (that siren has saved me a ton of money over the years when kelp covers the water pump inlets). I stopped immediately and lifted the leg to check for weeds. All clear. I fired back up after letting it cool and it went 300 meters before the siren went off again. The tattle tale was working but took a while for water to show up and it was HOT water. I shut it off again and let it cool. Then I tired to limp in at about 1,800 rpm. The tattle tale ran but not at the pressure I'm used too and it stopped briefly a few times. I limped it back to the marina and now I have the leg off in my garage and the thermostat out on my bench. I ordered new ones but they won't be here until tuesday ish.

My water pump impeller looks like i installed it yesterday despite being in the engine for 6 years and the thermostat is black and crusty but it does open when you put it in boiling water. The poppet valve diaphram looks a little brittle but not too bad it is also on order. I am starting to worry that there might be a bigger issue?

Is there anything else that affects over heating?

The boat is well maintained and ran like a top. It is using injector oil like it should be and I am pretty sure i didn't do any damage by limping home because I stopped whenever the siren went off and allowed it to cool.

Thanks!
 
Head gasket?? do a compression test on all cylinders,plugs out,battery fully charged to obtain 200-300rpms. Pull plugs first to look for water droplets,steamed cleaned ?? Usually head gasket.
 
There is no head gasket on that motor. Sounds like a salt water motor is it plugged anywhere. Could be something in the intakes that you can't see or made it through the pump into the motor. With the thermostat cover and lower unit off try pushing water through with a garden hose. I am assuming it's a 4 cylinder 2+2 motor.
 
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Yes it is a four cylinder in line. 2+2meaning it runs on 2 at idle and 4 at full speed? Yes I'm pretty sure it is. It goes to salt for about 2 weeks a year and is well usedin freshwater lakesthe rest of it's life. I am still hopeful that the thermostat and water pump will fix it, but I am a little skeptical based on their appearance. I will try the garden hose as soon as I go out to my shop.

Thanks

jeff
 
No problem with water flow. It takes a while to fill the water jacket but it flows readily out the thermostat, tattle tale and poppet valve. I am still waiting on a thermostat seal so I can't water test yet.
 
Solved in the second post. (failed seal) with parts driven to very top of water pump down shaft by the water pressure.
 
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