# Hard starting 20HP Mercury



## thomasr (Mar 26, 2018)

I recently picked up a 1988 Merc 20HP. It had been sitting for about 3 years so I went ahead and rebuilt the carb and water pump. Got it running but it's really hard to start cold. It runs like a champ after I give it a big squirt of gas down its throat and baby the throttle for a bit. So I was doing a little research on fixes and came across a couple posts on here that got me thinking. My Merc doesn't have the traditional choke as most know it...it has the "enrichment system". It has a pull handle labeled "choke" and the turning knob on the handle is supposedly the idle adjustment. I got the impression it's a bit more of a precise series of actions to get this to start. Can someone smart on Mercurys elaborate? I saw one post that said something to the effect....prime the bulb good, turn the idle adjustment all the way to the right, pull the choke to the second detent to activate the primer button, turn the hand throttle to the fast position, pull the rope twice, then push the throttle to the first detent, then it should start. Is that the process? I'd try it right now but it's raining. I'm having a little trouble getting my mind wrapped around this "enrichment" system. It runs too good to be anything major, so maybe its just an operator not being familiar with Mercurys issue. Thanks.


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## overboard (Mar 26, 2018)

Just going to throw this at you to check! My fishing buddy bought a boat with a 15 Merc that was hard to start, seems like when you pull the choke out there is a part of it that pushes on a plunger, which would be the "enrichment system". The plunger was stuck and wouldn't push in like it should, I sprayed the plunger and gently tapped on it and it freed up, which also then let the choke knob pull out further because it could now push the plunger in. His has the same setup as you are describing, that was his problem and may not be yours, if you are getting to the second detent on the choke it's probably not the problem.


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## JMichael (Mar 27, 2018)

That primer system uses a diaphragm to give a squirt of fuel to the carb. If the little plunger isn't stuck (as mentioned above) it could be a busted diaphragm. So check to make sure it's actually getting that shot of fuel into the carb.


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## Carphunter (Mar 27, 2018)

Hey Thomasr, I have an early 80's Merc 25 that is new to me. I did the same thing, rebuilt carb and water pump. I had the same problem, hard to start. After running, it would start every time while on the water, but next day the same problem. If I used the choke, or in my case the fuel enrichment valve, the motor would flood. Now I pull twice with no choke at all, then dial the choke two or three clicks and she starts right up. Try without letting the choke hit that plunger. Good luck! Let us know how this turns out.


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## thomasr (Mar 27, 2018)

Thanks folks for the replies. Part of the carb rebuild included replacing everything in the primer enrichment system, so the diaphragm is new and the plunger moves freely. That said, how do I know if it's actually squirting a shot of fuel in the carb? I can't see in the there...I don't really hear anything either. I've gathered from here and other sites that flooding can be a concern with this system. In my case I'm a little skeptical because when I manually squirt fuel into the carb I'm putting a really healthy shot in there. If it was going to flood I'd think I'm running more of a risk with my squirt bottle. 

Carphunter, you said "then dial the choke two or three clicks and she starts right up". Sorry to be so dense here but what do you mean? Do you mean turn the idle adjustment? My choke is the pull type with two positions. The first position appears to retard the timing a little and bumps up the idle/throttle. The second position does the same, but this time it pushes down and holds the primer plunger. My idle adjustment doesn't have actual clicks, it just turns. Sorry if I'm being too literal. What experience I do have with outboards is more of the Johnny-Rude and Gamefisher flavor. Thanks again folks.


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## onthewater102 (Mar 27, 2018)

PM Sent in reply to your PM.

You should be able to prime the fuel line until the bulb is hard, then when you pull the enrichment knob out you should hear a squirt of fuel go into the carb. Push the knob back in then try to start it. Leaving it pulled out it will flood - it is not a choke.

The enrichment valve bypasses the jet and allows the pressure in the fuel line to introduce a small amount of fuel into passages that get to the carb throat.

If you have a knob on it do not pay it much mind, it changes the timing advance slightly - that's all and it's really not needed. Later models didn't have it.


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## thedude (Mar 28, 2018)

This version?


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## onthewater102 (Mar 28, 2018)

That looks like it, though I cannot say for sure because my motor came to me with camo paint on it, so I'm unsure what the original decals would have been.

Held open the enrichment valve opens a passage for additional fuel to flow into the carb body - with it held open only a few unsuccessful attempts to start will be needed to flood the motor, especially in the cold.

When I used my motor last November/December the early morning temperatures were well below freezing (~23 deg if I recall) when I headed out and it took a squirt of starter fluid to get the motor going. I couldn't get it to fire up in the cold without the starter fluid but with it the motor started on the 1st or 2nd pull like it does every other time I use it. I've never needed the starter fluid for temperatures around freezing or higher.


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## thomasr (Mar 28, 2018)

Well a big thank you to everybody for your help and guidance cause we figured it out. There's a hood (for lack of the proper term) right in front of the carb inlet that kind of directs air. It attaches along with the racket adjustment lever and the primer lever...the enrichment assembly. The whole thing is held on by two screws. I can take the hood off but have to put the two screws back in to hold the rest of the parts on. Well, without the hood, the two screws don't bottom out and stick out a ways. I took the hood off hoping I could kind of see things better and get a clue as I was trouble shooting my hard start problem. Well, yesterday I had a visual epiphany. I noticed that when I pulled the "choke" out, the racket adjustment lever was getting caught on the head of one of the screws and not coming all the way back as far as it should. This racket lever pulls the time retarder for easy start and the throttle linkage for fast idle. With the lever hung up, neither was being fully actuated. I put the hood back on and everything works as intended. After I got all that sorted out, it started on the second pull. Next day, today while stone cold, it started on the second pull. Waited two hours and it started on the second pull. Other than being a cold natured hussy I think I got her. Thanks again y'all.


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## overboard (Mar 28, 2018)

Good to hear you figured it out.


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