25hp 1980 Merc - Correct Starting Procedure?

[Cordovakid]

Hey Guys - my 1980/81 25hp Merc is very, VERY difficult to cold start. Warm is OK - only one pull needed. But cold starts are not nice. I have the OEM Svc. Manual, but not the owner's manual, so I don't have access to the "OEM Starting Procedure", as it were. This model has a Tillotson BC1C carb, with the plunger-type enricher built into the carb, which is depressed by an arm when the idle knob is turned all the way clockwise to a higher idle speed. I understand this particular type of enricher operates on a vacuum principle, by pulling the fuel into the carb instead of pumping it in like a push/pull type of knob.

Anyway, since there's no formal "choke", I don't know if I'm flooding it or not giving it enough fuel most of the time, but after 25 pulls or so, it'll start. I typically turn the primer "on" four or five times and then leave it there with the plunger depressed, and try to start 'er up. Sometimes I will deactivate the plunger and just leave it on high idle to get it going, but doesn't seem to make much difference. I realize it probably needs a carb / fuel pump cleaning, which I will do in the spring, but for now I would like to make sure I look at the easy things first.

Does anyone have access to (or knowledge of) the "correct" starting procedure for one of these types of older enricher carbs? My right arm thanks you...

 

[ajgraz]

Re: 25hp 1980 Merc - Correct Starting Procedure?

...I realize it probably needs a carb / fuel pump cleaning, which I will do in the spring, but for now I would like to make sure I look at the easy things first...

Most likely nothin' will be easy about starting that motor cold until you do this.

 

[Mi duckdown]

Re: 25hp 1980 Merc - Correct Starting Procedure?

Pull out the the choke knob push it back in. do that three times. then turn that knob clockwise and pull rope. ifthat don't work, your enricher is bad.. Ten bucks to rebuild enricher. NO Need to rebuild carb. Have you removed the hood to see if it is pushing on the choke/enricher plunger?

 

[Cordovakid]

Re: 25hp 1980 Merc - Correct Starting Procedure?

Yes, the rod arm is coming down and pushing on the enricher as I turn the knob all the way clockwise, which also allows the idle speed to increase at the same time. My suspicion is that the enricher is either plugged (needs cleaning) or is not fully pushing all the way down to allow the fuel to travel to the carb throat. I have been leaving the enricher plunger pushed down while I pull start, thinking that the manifold vacuum might draw extra fuel in while I'm cranking - does this make sense? How exactly does the fuel in this type of enricher get delivered to the carb when the plunger is depressed? Any other thoughts than a clogged enricher?

 

[Mi duckdown]

Re: 25hp 1980 Merc - Correct Starting Procedure?

Look in the carb throat and manually push down on the plunger with your finger. You should see mist of fuel if not rebuild the enricher pump. There is NO manifold vacuum.