1984 - 120 Mercruiser - Choke problems

[sonny08]

Yellow metal ticket on the Carb reads - Mercruiser MCM 120/140 - 1389-8490
this is a 2 barrel carb.

Some quick back ground on this boat - had been sitting for 6 years - Boat had been properly stored by it's previous owner. I removed the old stabilized gas, put in fresh gas & STP cleaner & moisture remover. Did a full tuneup - points - rotor - plugs - wires - cap - t/stat set the dwell & the engine purrs like a champ on the muffs. I will set timing once it's in the water.

The electric choke appears to be not working - I removed the case & did a continuity check on the coil insert inside the case, checks ok. Wire connections are clean.

Wondering how this electric choke is suppose to work & why it's not working


Thank you

Sonny

 

[jtybt]

Re: 1984 - 120 Mercruiser - Choke problems

Remove the connector and check voltage to ground. Maybe bad connection at the coil(+)

 

[Maclin]

Re: 1984 - 120 Mercruiser - Choke problems

Electric chokes use electricity to heat the choke and open the carb's choke plate (turn the choke off) at a gradual controlled rate. There is a mechanical link from the choke's bi-metal coil to the plate. The choke's bi-metal coil also has a small electric heater in the housing. When the choke's coil is cold the linkage holds the choke plate closed at the top of the carb. Anytime the ignition is on there is power to the heater and the choke bi-metal coil will begin to unwind and work the linkage to open the choke plate.

 

[Maclin]

Re: 1984 - 120 Mercruiser - Choke problems

I need to qualify my last post...that is how electric chokes work on automotive based I/O engines. On outboards the choke button actually chokes the engine so if you are used to that then the "electric choke" for I/O style engines works backwards.

 

[sonny08]

Re: 1984 - 120 Mercruiser - Choke problems

Will check voltage , if voltage is correct - is changing out the coil sensor the usual fix?