Mercury V150 overheating

[hillclimber61]

This is a 1984 XR2. Running at 5000 RPM Horn sounds I idle for a few and it goes off. Get back to 5000 it sounds again within 1 minute. The horn always goes off if I idle. The the sensor was replaced and it still happens. no difference. Took thermostats out and it took longer for horn to sound but it still rang. Idling is the only thing that stops horn. thermostats are back in<br />Mix my oil<br />thanks<br />Fred

 

[rodbolt]

Re: Mercury V150 overheating

hello<br /> could be a number of things. a melted/defective pump bad t-stats, bad or stuck pressure control valve or salt/sand in the water passages. go by bills marine in portsmouth and pick up a melt stick. if Bills does not have it Rons marine on rodman av in portsmouth does. that way you can id what part of the motor is actually getting hot<br />]

 

[hillclimber61]

Re: Mercury V150 overheating

thanks for reply<br />I have a thermo gun and tried to find hottest area<br />I removed the right side of motor including the head and found that side to be clean. Ran motor in my tank and heads were running at about 138-147 degrees. Took boat for a ride and tried to check temp while horn was blowing and still got about the same temp 150s Did notice that water pressure at my gauge was pegged near 30 at 5000. Normally at idle I have 10-15 and at 5000 I have 15-20 Today with the temps around 22 degrees and water temp around 42 the horn sounded quickly<br />1-3 minutes after full throttle with water pressure pegged at 30<br />thanks

 

[rodbolt]

Re: Mercury V150 overheating

test the sensors. one head has a switch the other may contain a sensor. the two look very much alike. the alarm works on the switch. the switch should show no continuity. when heated to about 240 degrees. not sure about the specific number but is going to be between about 180 and 240*F. could be a bad or incorrect temp switch.<br /> have you tried unplugging the tempo switch while the horn is sounding. if your temp gun says its cool then odds are its not overheating last one I chased was actually a localized hot spot caused by a piston dragging.

 

[hillclimber61]

Re: Mercury V150 overheating

my engine has only one sensor. It operates the horn It was replaced because I thought it was bad.<br />Horn still sounded with new sensor

 

[hillclimber61]

Re: Mercury V150 overheating

found stuck pressure control valve. Too corroded to clean need to replace. Does anyone know of a good parts place (on line or otherwise)where I can get a new one along with some thermostats<br />thanks

 

[DHPMARINE]

Re: Mercury V150 overheating

As always I suggest... support your local dealer.You may need him some day.<br /><br />DHP

 

[gss036]

Re: Mercury V150 overheating

http://www.mercurypartsexpress.com/PartsExpress/HomePage/homepage.asp <br /><br />Follow the link, you can find the parts and order<br />online and pick them up at your closet dealer. They give you a little price break for doing this. Service is pretty fast.<br />I was just reading up on the cooling system, the alarm goes off at 240 degrees and then will stop when it cools to 210 degrees. Definately sounds like you have a water flow problem.