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Author Topic:   1980 Mercury 50-HP Overheating

bullet posted 11-09-2009 12:16 PM ET (US)
Took my 13 out yesterday and ran about 10 miles down the lake. I have a 1980 Mercury 50-HP in-line four-cylinder on her. I ran the boat at cruising speed the whole 10 miles trying to beat sundown, sometimes putting my hand in the throttle a little heavy. When I backed off the throttle at the ramp I noticed the water coming out the [tell-tale stream] was smoking hot. I felt the water and it was hot, not enough to scald you, but pretty hot! I took the cowling off and felt the block,; it was about like the water, not enough to burn you but hot. I noticed when I cranked the engine before I went out, the water pump stream looked kinda weak.
Was the motor running hot?
In all my years of boating I don't think I ever remember the water being that hot coming out the [tell-tale stream].
Do you think I need a water pump?
Is the water suppose to be that hot coming out the [aspirator or tell-tale or confidence stream nozzle]?
Like I said, the motor was not scalding hot but seemed to be on the warm side. I did run it non-stop for 10 miles, and it ran great, but I am a little concerned on the heat. I have never put a water pump in the engine. I have had the motor four years and it always had a good stream. It is only the second time I used boat all year, been battling Lyme disease.
What do you guys think?
Time for Pump?
Sure was beautiful on Lake Wateree SC yesterday, best I have felt in two years was on my Whaler yesterday! Thanks all,Dave.
R T M posted 11-09-2009 01:18 PM ET (US)
Yes, its time to replace the water pump. The block should never be so hot that you can`t hold your hand to it. You should do it by the manual, and save some aggravation

rich/Binkie
bullet posted 11-09-2009 01:36 PM ET (US)
Thanks Rich.You reckon that is all it is? I can't think of anything else it could be.
Tohsgib posted 11-09-2009 02:02 PM ET (US)
If it was anything else it would have really been hot. I would check the thermostat when you replace the pump. Usually you can get away with just an impeller, not a whole pump if housing and plates are pretty clean and smooth. Second, if you ran it hard then shut it down it will be hotter than if it had a few minutes to cool off at idle or above that.
bullet posted 11-09-2009 02:28 PM ET (US)
Thanks Biggie. I did idle about 10 minutes through no wake zone before feeling block. Still felt hotter than normal. Had steam coming out [aspirator or tell-tale or confidence stream nozzle] with water. Motor been in salt water twice in its life, always flushed! Think thermostat could be bad? Dave
Tohsgib posted 11-09-2009 02:35 PM ET (US)
Probably not but check them when you do the impeller. Steam is hot--not borderline hot.
Buckda posted 11-09-2009 03:03 PM ET (US)
Mercury engines are known to have the confidence stream become warm when the engine has reached temperature.
The design of the Mercury system is such that the confidence stream does not exhaust water until it has flowed throughout the cooling jacket, so the water emitted is water that has transferred the heat of the block already. OMC/Evinrude's old system had a "T" fitting right off the water pump housing and would emit cold water from the pump directly. The stream started immediately when you started the engine and the pump was working.
I think that you should consider replacing the water pump on a set regular basis based on time, not hours. i.e. every-other-year is not a bad rule of thumb.
I had a 1978 version of that motor and the exhaust water was always warmer than the lake, and on hot days, it was considerably warmer than the lake. On very cold mornings, when running it hard and coming off plane, it would "steam" for awhile as the lower volume of water circulated around the still warm powerhead and transferred more of that heat per unit of water.
I dont' think it is unusual.
tedious posted 11-09-2009 03:44 PM ET (US)
If you don't know when the water pump and thermostat were last changed, then it's time to do both of them.
Tim
bullet posted 11-09-2009 03:50 PM ET (US)
Thanks guys, I feel better! Will replace water pump. I guess I have never run boat in cool water, I always run it in the summer. The water being colder and the stream steaming kinda through me. Guess I don't notice it in the summer cause the water is warmer. Was looking for thermostat on line and can't seem to find any for the 4 cylinder 50 HP. Have to look at motor when I get home.

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Author	Topic: 1980 Mercury 50-HP Overheating
bullet	posted 11-09-2009 12:16 PM ET (US) Took my 13 out yesterday and ran about 10 miles down the lake. I have a 1980 Mercury 50-HP in-line four-cylinder on her. I ran the boat at cruising speed the whole 10 miles trying to beat sundown, sometimes putting my hand in the throttle a little heavy. When I backed off the throttle at the ramp I noticed the water coming out the [tell-tale stream] was smoking hot. I felt the water and it was hot, not enough to scald you, but pretty hot! I took the cowling off and felt the block,; it was about like the water, not enough to burn you but hot. I noticed when I cranked the engine before I went out, the water pump stream looked kinda weak. Was the motor running hot? In all my years of boating I don't think I ever remember the water being that hot coming out the [tell-tale stream]. Do you think I need a water pump? Is the water suppose to be that hot coming out the [aspirator or tell-tale or confidence stream nozzle]? Like I said, the motor was not scalding hot but seemed to be on the warm side. I did run it non-stop for 10 miles, and it ran great, but I am a little concerned on the heat. I have never put a water pump in the engine. I have had the motor four years and it always had a good stream. It is only the second time I used boat all year, been battling Lyme disease. What do you guys think? Time for Pump? Sure was beautiful on Lake Wateree SC yesterday, best I have felt in two years was on my Whaler yesterday! Thanks all,Dave.
R T M	posted 11-09-2009 01:18 PM ET (US) Yes, its time to replace the water pump. The block should never be so hot that you can`t hold your hand to it. You should do it by the manual, and save some aggravation rich/Binkie
bullet	posted 11-09-2009 01:36 PM ET (US) Thanks Rich.You reckon that is all it is? I can't think of anything else it could be.
Tohsgib	posted 11-09-2009 02:02 PM ET (US) If it was anything else it would have really been hot. I would check the thermostat when you replace the pump. Usually you can get away with just an impeller, not a whole pump if housing and plates are pretty clean and smooth. Second, if you ran it hard then shut it down it will be hotter than if it had a few minutes to cool off at idle or above that.
bullet	posted 11-09-2009 02:28 PM ET (US) Thanks Biggie. I did idle about 10 minutes through no wake zone before feeling block. Still felt hotter than normal. Had steam coming out [aspirator or tell-tale or confidence stream nozzle] with water. Motor been in salt water twice in its life, always flushed! Think thermostat could be bad? Dave
Tohsgib	posted 11-09-2009 02:35 PM ET (US) Probably not but check them when you do the impeller. Steam is hot--not borderline hot.
Buckda	posted 11-09-2009 03:03 PM ET (US) Mercury engines are known to have the confidence stream become warm when the engine has reached temperature. The design of the Mercury system is such that the confidence stream does not exhaust water until it has flowed throughout the cooling jacket, so the water emitted is water that has transferred the heat of the block already. OMC/Evinrude's old system had a "T" fitting right off the water pump housing and would emit cold water from the pump directly. The stream started immediately when you started the engine and the pump was working. I think that you should consider replacing the water pump on a set regular basis based on time, not hours. i.e. every-other-year is not a bad rule of thumb. I had a 1978 version of that motor and the exhaust water was always warmer than the lake, and on hot days, it was considerably warmer than the lake. On very cold mornings, when running it hard and coming off plane, it would "steam" for awhile as the lower volume of water circulated around the still warm powerhead and transferred more of that heat per unit of water. I dont' think it is unusual.
tedious	posted 11-09-2009 03:44 PM ET (US) If you don't know when the water pump and thermostat were last changed, then it's time to do both of them. Tim
bullet	posted 11-09-2009 03:50 PM ET (US) Thanks guys, I feel better! Will replace water pump. I guess I have never run boat in cool water, I always run it in the summer. The water being colder and the stream steaming kinda through me. Guess I don't notice it in the summer cause the water is warmer. Was looking for thermostat on line and can't seem to find any for the 4 cylinder 50 HP. Have to look at motor when I get home.