Engine only runs with choke on

[Rocjohns]

I have posted a few other questions to the group and all solved my problem...

I have a 69 Johnson 25 hp. Coils/points/condensers changed and all electrical system works great.

Bought a new fuel pump, but it said it was the model for a 15 hp outboard of same year. Seems to be pumping fine though.

Finally got her running and let her run for an hour or so and idles fine with choke open. Obviously I can't throttle up with choke open because runs terrible. Went to close choke and it dies.

Now, it looks like it had a rebuild kit done to it and I also took it all apart and soaked it with carb cleaner, but I am not sure about behind the metal punch-out pieces of the carb.

I was considering buying a new rebuild kit so that I could check behind the metal punch-tabs for gunk.

Is there anything else that I am missing here? Also, could it be low compression? It feels like it sucks air good from the reed plates.

Thanks again...

 

[racerone]

Re: Engine only runs with choke on

Choke open means what here ?---It does seem confusing.

 

[Rocjohns]

Re: Engine only runs with choke on

Sorry about that.

There is a manual choke on these engines. Normally you have to open choke to start. In my case, it idles fine with choke engaged, open, etc...
If I try to disengage the choke, it seems to be robbed of fuel and dies.

Does that make sense?

 

[kbait]

Re: Engine only runs with choke on

Sounds like main jet is partially clogged. It's directly behind the drain bolt on carb bowl. You could try removing that bolt, and probing through the jet w/thin wire to unclog it and test again.

Good luck!

 

[Chris1956]

Re: Engine only runs with choke on

Actually, it sounds like the idle circuit is clogged. In any case, the carb needs to be disassembled, cleaned and reassembled with new gaskets and any new parts necessary.

 

[Rocjohns]

Re: Engine only runs with choke on

Is the idle circuit behind the metal knockout plugs/tabs (I am not sure what they they are actually called)?

 

[racerone]

Re: Engine only runs with choke on

Sorry , but when trying to start this motor the choke flapper should be CLOSED ---that is why your verbal description is confusing here.

 

[Rocjohns]

Re: Engine only runs with choke on

Sorry if it is confusing. It's open. When I pull the choke pin out, it opens it up. When I disengage choke, it closes it.

Does that make sense?

 

[Daviet]

Re: Engine only runs with choke on

No it doesn't. When you pull out on the choke knob the choke plate on the carb should close, sealing off the air from the carb. When you push the choke knob in, the choke plate in the carb should be wide open, allowing air into the carb.
Yes, the idle circut is under the little core plug on top of the carb, your kit should have had a new core plug in it. There are tiny passages under the core plug that have to be clean or the engine will not idle properly.

 

[BonairII]

Re: Engine only runs with choke on

Sorry if it is confusing. It's open. When I pull the choke pin out, it opens it up. When I disengage choke, it closes it.

Does that make sense?

Think of the choke in terms of choking a person. When you choke a person...you cut off their air supply. That's what the choke does on a motor...it allows less air in....it doesn't add more fuel to the existing fuel/air mixture.

Engaging the choke....closes the plate over the carb throat.

If pulling your choke pin out actually opens up the throat plate(rather than closing the throat)...maybe it's installed incorrectly???

 

[Rocjohns]

Re: Engine only runs with choke on

Ok, this seems to be my confusion. I have it backwards then and kills my idea that choke needs to stay on for it to run.

It purrs on idle then; however, if I give it any major throttle in my barrel, it Boggs down quite a bit.

Scenario's that could possibly make it run poorly would be

A. Fuel pump not getting enough gas to carb?
B. Still clogged carb?
C. Low compression?

Was planning on doing a full carb rebuild and doing the Seafoam tank/ head/ carb job. Also was going to check compression tomorrow.

 

[Rocjohns]

Re: Engine only runs with choke on

So I was researching my fuel pump...

Mine calls for 0382875. Searched for it and said it was obsolete. A new part number was used. 0388685.

I searched for that one and somehow I bought model 391667 which the listing said it replaces 0388685; however, it says it's rated for 9.9/15 hp. Fairly confusing.

Could this be my issue?

 

[BonairII]

Re: Engine only runs with choke on

Your timing is probably NOT advancing properly. Bogging is most likely NOT from lack of fuel.....but is lack of spark(at the correct time).

Run the motor and when the motor bogs, pump the fuel ball....if the motor perks up....you have a fuel delivery issue(clogs, fuel pump, etc etc)....if not, fuel delivery is fine.


Don't buy ANY parts until you have the culprit.

 

[Rocjohns]

Re: Engine only runs with choke on

Man, I wish I would have gotten that advice earlier. Will probably be taking a few parts back tomorrow if it is just a timing issue.

I will check in the morning and let you know. I have a feeling this is going to solve my last problem...

 

[Rocjohns]

Re: Engine only runs with choke on

So that was it. Set the timing based off YouTube video I found. The guy even said that iboats.com showed him how to do it.

It ran well and idled well. What really, put it over the top was the Seafoam treatment. Found a new can they make that is actually a spray. Put it in the head for 15 minutes to soak, then fired her up. Then as it was running, sprayed it in the carb while pulling the throttle cable. I am sure my neighbors were worried that my house had caught fire. I did this for a while then just burned the rest out. Went from idling well, to purring like a new born kitten. Looking forward to taking her out.

http://m.youtube.com/watch?v=ga1Cjymj6ms

Thanks again,
Bobby

 

[yorab]

Re: Engine only runs with choke on

They say it's not good to throttle up to high revs in a barrel. It could result in a runaway condition that can damage parts.