Mercury Switch

[Sean Leonard]

I recently purchased a well used 1978 Mercury 800 80hp outboard. The internal wiring is a mess. I am curious to know what the "Mecury Switch" does. I am going to need to replace the switch because there is only one wire left on it and it's badly worn.

 

[Bob_VT]

Re: Mercury Switch

It will kill the motor when it is tilted........ in the event it is ever tilted while running the water pick up would be out of the water. It is a safety device so your motor does not overheat and self destruct

Welcome to iboats

 

[Sean Leonard]

Re: Mercury Switch

Thanks Bob. Do you know if the circuit is NO or NC?

 

[Silvertip]

Re: Mercury Switch

Magneto ignition systems are killed by grounding them so the switch with the engine in the RUN range of the trim system would need to be N.O. When the engine tilts too far the switch "closes" killing the the ignition.

 

[Faztbullet]

Re: Mercury Switch

Its also a safety switch in case you hit a object and break the restraint strap, keeps a running engine from entering boat. And it does happen as I have seen a 225 HPDI on a Ebbtide snap the jackplate and land on rear deck!!!

 

[Sean Leonard]

Re: Mercury Switch

Is there a recommended maintenance or testing interval for the switch? Being a normally open circuit then I would assume one may not know the switch or wiring is faulty until it fails to kill the motor in an emergency.

 

[Faztbullet]

Re: Mercury Switch

It is called a Mercury switch as thats what is filled with, works like the filled vial on a indoor t-stat. I have never seen a bad one, just wires rotted causing it not to work.

 

[ThumbPkr]

Re: Mercury Switch

The old Maytag washing machines had a few in the top lid for controlling high water etc.I have bought them at the
Maytag dealer in the past.Ron G