87' 175 seems to be running warm...

[3car]

I just bought a boat with an 87' merc 175. I've been working on a few things before I put it in the water, but I did notice something when running it on the garden hose. The motor pee's a strong stream, but the water is hot. Its hot to the point that its uncomfortable to hold your have under it for more than a few seconds. The cylinder heads also get hot enough that its uncomfortable to touch them for more than a couple seconds.

This all happens within a couple minutes of initial start-up. I have a Mariner 20, and the pee water stays cool, as does the head for the most part.

 

[3car]

Re: 87' 175 seems to be running warm...

can someone atleast confirm that the water should or should not be this warm out of the pee hole?

i changed the head gaskets and thermostats today, but the old thermostats were functional.

 

[Plainsman]

Re: 87' 175 seems to be running warm...

The only thing I can help you with is the water shouldn't be that hot.

 

[gss036]

Re: 87' 175 seems to be running warm...

Are you talking running the engine on a hose? What RPM are you running at?
T-Stats open at 143 degrees. That is about 25 degrees hotter than you hot water tank. Have you checked them to see if they are opening properly?
You have good pee stream, do you have a water pressure guage? If so what kind of pressure do you have?
You can always get temp wax stick and see if it melts on the head. That will give you an idea of where you are w/temp. I think the overheat sensor goes off at about 240 degrees.
The older Merc's do seem to run on the warm side.

 

[3car]

Re: 87' 175 seems to be running warm...

Are you talking running the engine on a hose? What RPM are you running at?
T-Stats open at 143 degrees. That is about 25 degrees hotter than you hot water tank. Have you checked them to see if they are opening properly?
You have good pee stream, do you have a water pressure guage? If so what kind of pressure do you have?
You can always get temp wax stick and see if it melts on the head. That will give you an idea of where you are w/temp. I think the overheat sensor goes off at about 240 degrees.
The older Merc's do seem to run on the warm side.

good pee stream, new thermostats.

 

[3car]

Re: 87' 175 seems to be running warm...

Come on guys... I need some input. Here's the latest.

I now have a key for the boat, so I am starting it from the control box. I have a quicksilver temp gauge which goes to just under half with about 10 minutes of ideling on the hose. However, the beeper on the control box comes on immediateld following start-up. Even if the engine is completely cold.

I have replaced the head gaskets and thermostats. The pee stream is strong, but its hot enough to make coffee with!

Free cup of coffee with each reply!

 

[jebeebe]

Re: 87' 175 seems to be running warm...

It should come on and beep once as a test to show it is working, but not continue. I take mine black................Jerry

 

[gss036]

Re: 87' 175 seems to be running warm...

You did not indicate what type of beep you are getting. BEEP BEEP when you turn the key on is normal. Continuos beep-beep-beep-beep is not and indicates low oil alarm, or, that the oil pump is not working. Pre-mix if you are not sure if it is moving oil. I explained the one in the engine tank w/magnetic pick up, it just tell you when you are low on oil and like to stay at the top. Loosen the cap a turn or two and see if oil seeps out while the engine is running, is so retighten, just enough so it does not leak, too tight and it will split the cap. The tank on the boat is pressurized by the engine running and forces oil up the line to the tank on the engine. The oil from that tank is gravity fed to the pump where it is pumped into the mixing tee w/fuel and then to the carbs.

BEEEEEEEEEEEEEEEEEEEP continiously is overheat. I/2 rise of the temp guage at idle on the hose sounds about normal. There is a sender in each head, one is for the temp guage , the other is for overheat alarm.

 

[3car]

Re: 87' 175 seems to be running warm...

You did not indicate what type of beep you are getting. BEEP BEEP when you turn the key on is normal. Continuos beep-beep-beep-beep is not and indicates low oil alarm, or, that the oil pump is not working. Pre-mix if you are not sure if it is moving oil. I explained the one in the engine tank w/magnetic pick up, it just tell you when you are low on oil and like to stay at the top. Loosen the cap a turn or two and see if oil seeps out while the engine is running, is so retighten, just enough so it does not leak, too tight and it will split the cap. The tank on the boat is pressurized by the engine running and forces oil up the line to the tank on the engine. The oil from that tank is gravity fed to the pump where it is pumped into the mixing tee w/fuel and then to the carbs.

BEEEEEEEEEEEEEEEEEEEP continiously is overheat. I/2 rise of the temp guage at idle on the hose sounds about normal. There is a sender in each head, one is for the temp guage , the other is for overheat alarm.

its continuous. the sender in the right head is causing the alarm. which sender is that, overheat? it really dosent make sense if it is, cause it starts as soon as the engine does, even if it's completely cold. bad sender? the temp of the pee water still scares me though.

 

[jimc_LA]

Re: 87' 175 seems to be running warm...

3car, Here's whaat I can offer to help you figure this out.

On some mercs (mine included) the tell tale, or pee stream, is tied into the discharge side of the thermostats. This means that after a couple of minutes following startup the stats open and the tell tale stream is strong, but hot. My stats are 143 degree. Take a water sample and get a thermometer and check the temp. Mine was about 135 degrees and it was almost scalding to the touch. Yet, there was nothing wrong with the cooling system. It's just the way some mercs are piped for the tell tale. A lot of other manufacturers bring the tell tale off of a different source and it does not get that hot.

As far as the alarm beep. When you first turn the key to the "on" position the alarm will beep to let you know that it is working. If it beeps after you've started the engine that may indicate a problem. It may just be a faulty sending unit on the alarm though. You're engine shouldn't be getting that hot if just idling in the driveway on the garden hose.

When is the last time the impeller in the water pump was changed? Mercury recommends every other season or 100 hrs of operation, whichever comes first.

 

[gss036]

Re: 87' 175 seems to be running warm...

Normally the sender in the right head is the overheat sender.( it is not unsual to find them switched or swaped sides, really doesn't matter) It is a snap type device that will cool down and then reset. What happens is the end makes contact with metal, which grounds out the device and causes it to send a signal. There should only be one wire, if there are 2, then it is the temp sender for the temp guage. Follow the wire, it will go to a junction box. Disconnect it and the signal should stop. Check for ground or wire touching metal. Take the sender out if it stops and you cannot find/see anything wrong, you might just have a bad sender. They are very simple devices. The temp signal works on restentece caused by the heat.

 

[3car]

Re: 87' 175 seems to be running warm...

Ok, I played with it a little more. I used a meat thermometer and discovered the temp from the P-Hole was just short of 140 degrees. The water coming through the prop on exhaust was much cooler.

Now, tward the end of my little "test session" I noticed steam coming from the tell-tale/pisser, and I rechecked the temp with the thermometer and it was over 160. The temp gauge on the dash was almost maxed out.
I shut her down thinking that the impeller may have been in bad shape, and given up. Dunno...

 

[3car]

Re: 87' 175 seems to be running warm...

Oh, and thanks for the replies. It all helps!

 

[The-Machinist]

Re: 87' 175 seems to be running warm...

I came very close to toasting my 85 johnson when the muffs vibrated off the motor during a test idle. something to look for next time

 

[3car]

Re: 87' 175 seems to be running warm...

I came very close to toasting my 85 johnson when the muffs vibrated off the motor during a test idle. something to look for next time

Upon reading this I wondered outside to to boat, ans suprise, suprise...

The muffs were only covering about 1/2 of the water inlets. Well, that issue is solved and I feel a little silly.

I also noticed a slight leakage around the bottom of the relief valve on the side of the motor.