Temp Warning Horn

[crash-proof]

Hi, I have a Bayliner 160 powered by a Merc 50.

Every time I head out I check the "pisser" and it flows OK. However, last week I got the dreaded horn (more like an annoying alarm clock buzz on mine). I shut down the motor for a few minutes, restarted and got the horn again. The water was flowing out of the pisser, just not as fast as usual. The temp of the water was lukewarm, which led me to believe that the motor was not overheating. I continued back to port with the horn blaring, and the motor ran just fine. (it was only a 5 min journey back).

Could it be that the thermostat is worn out and giving me false readings? Or the actual horn is shorted out? (the horn is located somewhere behind the dashboard).

And what is the easiest way to improve water flowing thru the engine? It could be that there's sand clogging it up. I certainly don't want to risk taking it out again and overheating. Is there some type of "plummer" snake that I can feed thru the pisser?

Thanks in advance.

 

[JUSTINTIME]

Re: Temp Warning Horn

check the sensor also
could be t-stat also or your impeller
when was the last time u changed the impeller

 

[Texasmark]

Re: Temp Warning Horn

My current engine is a 3 cyl 90 hp and should be very similar to yours. Mine has a stat and pressure relief.

(I have since learned that) the water for the pee tube comes from the exhaust manifold, not from the area served by the stat. The exhaust manifold has to be cooled as long as the engine is running so it is on a separate circuit.

So I get the horn also on my first outing with this used engine, look at my little telltale and it's just a peeing away. Was real confused at the time.

Back at home, the pot of water test for the stat told the story and with a new stat installed no more problems. It was stuck shut.

What I did find out was that I could get home (which I did) on the bypass or pressure relief valve. It'is driven off it's seat by water pressure so at higher rpm's and when the lower unit is moving through the water at moderate to high speed the engine gets cooled and the warning buzzer shuts down. That's what mine did, course when I got in the nowake zone it got hot again so I just turned it off and trolling motored in.

Mark

 

[crash-proof]

Re: Temp Warning Horn

Hey thanks for the replies as always.

Re the impeller, I don't remember when, it's been a while, on the other hand, I didn't do much riding last year nor in '05 so it shouldn't be an issue. My guess is towards the stat, since the water is going thru.

Question - is there a PDF with an exploded diagram of the 50/90 Mercs, which would help this uber-layman get an idea of where things are? I have no idea where the stat is and I don't think the manual is detailed enough to show. It would be nice to open up the lower end and see impeller condition too.

 

[andy6374]

Re: Temp Warning Horn

FYI:

Engines that get little use, still need to have impellers replaced every other season or so. You NEVER want to be in a position where you NEED a new impeller.

 

[yamamarinetech40]

Re: Temp Warning Horn

Ok, the FIRST thing to check on suspected overheat is putting your hand on the head near thermostat housing. If it's too hot to keep fingers on for a few seconds, then it's too hot...this will let you know if you have a false signal or real problem. If it is too how, first thing to do is pull thermostat. Is it corroded? Is there sand present there? You can even test with cig. lighter while holding in your hand(although not accurate, if it works with lighter without lots of heat, you know works). Don't be afraid to touch engine, just watch out for flywheel on some.