Whats a mercury switch and whats its purpose? Plesae help!!!

[hfd12]

I was having a problem were my 1974 mercury 650 with thunderbolt ignition would not start and i wasent getting any spark. the coil is cracked in diferent places and thought it was that but i disconected the "mercury switch " and it started right up . can someone help and anser what a mercury switch is and its purpose and do i need a new one. thanks

 

[westexasrepublic]

Re: Whats a mercury switch and whats its purpose? Plesae help!!!

Its mercury safety switch that keeps the engine from running when the motor is tilted too far forward.

 

[hfd12]

Re: Whats a mercury switch and whats its purpose? Plesae help!!!

when i have the switched hooked up the motor wont start but when i diconect it it starts every time. do i need this merc switch hooked up? or dose it need to be replaced before running the motor? so this switch is bacically a kill switch for the motor? thanks

 

[ajgraz]

Re: Whats a mercury switch and whats its purpose? Plesae help!!!

Yeah, the mercury switch is a kill switch. When it gets tilted too much, it makes connection inside and grounds out the ignition, killing the motor.

Sounds like either the switch is bad, making contact all the time; or, the switch is installed in the wrong orientation, that is, in an "already too tilted" position.

There should be a "slot" or hole on the body of the switch that corresponds to a "nub" on the powerhead to make sure that the switch is in the proper orientation. If that looks right, then take the switch off and test it with an ohmmeter; it should have no continuity when "upright", then get continuity when it is rotated maybe 60-90 degrees or so.

 

[Ski'nBlind]

Re: Whats a mercury switch and whats its purpose? Plesae help!!!

Mine is mounted to the engine on a about a 45 degree angle so when the engine is tilted up that far the switch "makes" and kills the engine. Is yours mounted at an angle or just straight horizontal? Try changing the angle.

I've heard you can run without them and choke the engine to kill it.

 

[sxmerc]

Re: Whats a mercury switch and whats its purpose? Plesae help!!!

Get rid of it. You don't need it.

 

[Fuzzytbay]

Re: Whats a mercury switch and whats its purpose? Plesae help!!!

The switch serves two purpose's, one it helps prevent accidental starting of the motor, when its in the upright possition, second, if the motor pops out of the water, while running ,it shuts the motor down preventing over reving. Personally I'd get rid of it.

 

[achris]

Re: Whats a mercury switch and whats its purpose? Plesae help!!!

Get rid of it. You don't need it.

..... Personally I'd get rid of it.

The engine manufacturer put that switch there for a very good reason.... To protect the engine. You definitely need it.

The part number is 87-33386A3 and less than $50.... That is very cheap insurance to stop grenading an engine.

Chris.........

 

[j_martin]

Re: Whats a mercury switch and whats its purpose? Plesae help!!!

It has two purposes:
1. To protect the engine in some circumstances.
2. To drive you nuts.

hope it helps
John

 

[hfd12]

Re: Whats a mercury switch and whats its purpose? Plesae help!!!

thanks. it was installed wrong. got it right now. thanks u all

 

[asm_]

Re: Whats a mercury switch and whats its purpose? Plesae help!!!

I, for one wishs for a mercury switch on my outboard. My didn't came with one, and I have already accidentally started my motor out of the water twice. It usually happen right after I pull my trolling motor out of the water and forget to drop the main motor down to its running position.

B