2006 Mercury 40HP 4 Stroke Overheating

[msweetman1]

I have a issue with the motor overheating at high RPM's. Temp goes above 170 giving me an alarm and causing sputter on the outboard. Before the issue happened ran into a sandbar on the Colorado river and quickly reacted to put motor in neutral. The stream out of the pee hole is very strong but did not test it for water temp coming out.

Can someone suggest what may be the issue and how to fix it?

Will post serial number tomorrow.

Thanks,

Mike

[SilverFox579]

Your cooling system is probably full of sand. Start by flushing the system, check stats for proper operation or replace, ensure poppet is smooth, and replace the water pump. What I'd do if it were mine.

[Kodiak16]

If it's sand then there is a good chance the water pump housing is damaged. Change the water pump housing, impeller and change the thermostat. I did the same and the sand ate he housing around the impeller shaft.

[msweetman1]

Thanks for the suggestions.

Would it be a pump or impeller issue even though there is good flow coming out of "pee" hole of the outboard?

[Kodiak16]

Could just be the thermostat stuck closed from debris. But I would check everything and flush the cooling passages in the block. Could be the intakes are clogged as well. At speed you might not be moving enough water. Overheat blow a head or worse not worth the risk. Check every part of the cooling system.

[msweetman1]

Thank you Kodiak.

Please forgive my ignorance, when you state flush the cooling passages in the block, do you mean attaching garden hose to the threaded connection where the pee hole is and flush system that way?

[berudd]

Yes, I think you could still see a tell tail stream even if you didn't have good enough water flow throughout the rest of the engine. If you've never replaced the water pump is overdue by now anyway so changing it is a good idea. Junk in the thermostat is also very possible.

[msweetman1]

Thanks for all the replies.

I will flush the system this weekend and replace pump and impeller also.

[EuropeanAM]

Let's back up a few days... as the country song goes, sometimes "tomorrow never comes".

Please provide the engine serial number before any further discussion. Thanks!

[msweetman1]

Will post serial numbers tomorrow. Thought it was overheating but engine cuts out on the higher RPM's. Maybe a ignition coil, spark plug, or something else electrical. Did reverse flush and motor stayed within 130 degree range but cut out as RPM's were increased past 3000.

[msweetman1]

Serial Number:

1C027044

[EuropeanAM]

Thanks. Couple of suggestions- probably a good idea to just go ahead and complete all of these items now, and then see where you are at:

-Remove thermostat, clean/test (or simply replace).
-Replace Water Pump
-Change engine oil and filter

Monitor temperature, warnings, and running quality carefully. Additional items MAY be required, but let's make sure we've covered these bases before going much deeper into anything.

[msweetman1]

Thanks European. I will go with what is suggested as a starting point.

[msweetman1]

How do I get rid of this clog? Can I use a garden hose and flush this down the motor or is there something special that needs to be done?

Thermostat Cog


Another shot

[SilverFox579]

Though I don't know exact cooling system circulation of your engine, I would think you could attach muffs to engine (not running!) and flush with thermostat and cover removed. Your cooling system is definitely full of sand as I said in reply #2. Might be effective to flush with muffs then use the flush port and repeat process as many times as necessary until all sand is out. Don may have a better method.

Need to get all the sand out, and with that much sand in the system I'd replace the water pump AND thermostat without a second thought.

[msweetman1]

Thanks Silver Fox. I already have thermostat and water pump on order as we speak.

There is a attachment on the back of outboard where the pee hole is to attach a hose to flush system. Can I flush using the mentioned spot or go with the ear muffs?

[SilverFox579]

The flush port back flushes the engine and should never be used with the engine running. Using muffs will provide water flow same direction as water pump. My thought was alternating between the two might help get all the sand out more effectively. I don't know if your engine uses a poppet valve, so hopefully Don will comment on that and his flushing recommendations. Hope that helps.

[msweetman1]

Thanks Silverfox. I will do both flushes. Regarding the poppet valves, I don't know if my motor has them, trying to get a definite answer on that. One site says no and another says yes.