Push to choke ign. sw,chokes only in start?

[crappiejig]

Hi all,I have just completed a carb rebuild and sync of my neighbors 1996 merc 50hp 4 stroke.This is not the original engine,it had a 2 stroke originally,its a bass tracker 16ft.The ign switch is dash mounted,and will only activate the choke solenoid in the start position,whereas all my previous boats the choke will activate in run also.This 4 stroke also has a "Thermo electric Plunger" mounted beneath the choke solenoid.My service manual gives no description on how this item works to presumably enrichen the mixture.Does my neighbor need a new ign. switch? The engine runs smooth,but when cold starting it takes several attempts. Thanks for any thoughts!

 

[Texasmark]

Re: Push to choke ign. sw,chokes only in start?

Logic makes me want to say get a new switch and maybe have a look at the wiring for the 4 stroke. I don't know who designs Merc's 2 and 4 strokes. One would think if the same people, their mindset would be the same.

It makes sense to be able to hold the choke function (be it fuel enhancement or whatever) prior to attempting to start, and have it remain activated during the starting attempt if you continue to push and hold the choke switch. It also makes sense to be able to reintroduce raw fuel after starting when the engine starts lean sneezing so you would want to be able to activate in in the Run position then too.

But, one would ask, is it just a coincidence that this function stopped at the same time you changed engines? Makes you wonder.

Mark

 

[crappiejig]

Re: Push to choke ign. sw,chokes only in start?

thanks mark.As its my neighbors fathers boat,will have to ask him if the switch was changed along with the engine.Any merc 4 stroke owners (carbs) out there that can tell me if they can choke a running engine to help it along? Prety sure this powerhead is yamaha built but not sure if merc added the carbs or if yamaha supplied them.By the way the thermo electric plunger I mentioned is also referred to as an auto starter in the svc manual.

 

[crappiejig]

Re: Push to choke ign. sw,chokes only in start?

Found the answer in the wiring diagram.Choke solenoid positive wire shares the same side of the starter solenoid as the starter motor positve.Only chokes while starter is acivated.

 

[Texasmark]

Re: Push to choke ign. sw,chokes only in start?

Ok, I can go along with that for a "Choke" solenoid. Doesn't make sense to have it energized when there is no induction through the carb intake ala, no engine turnover. But you don't have any backup for a sneezing lean/cold engine.

Enter the fuel enrichment function. Switch on, push, energizes the enrichment solenoid which dumps fuel into the intake manifold via the carbs. 30 seconds of that and roll the start switch over to start and the engine starts while still getting additional fuel until you quit pushing on the start switch. Then after starting if it starts sneezing, pushing the start switch will again energize the solenoid and pump additional fuel again till you let off.

My engine has the enrichment function but it is a 2 stroke. I guess those 4 strokes get treated differently.

Mark