HELP --- Carb. adjustment on 4.3 alpha one

[KCChris]

I need advice on carb adjustment, when motor runs it runs a little rough. I am getting a little dark exhaust smoke. Is it running rich or is this caused by choke out of adjustment. I'm not sure how to adjust out of it. This is a 2bbl Merccarb. Boat sat for over a year, I've replaced fuel pump, completely disassembled,cleaned and reassembled carb. Not sure where to go next.

 

[lorax]

Re: HELP --- Carb. adjustment on 4.3 alpha one

I'm not much of an authority but I've been wrestling with a similar problem. <br /><br />You should probably check the resistance across the electric choke windings. I don't have my manual with me but I think it's suppose to be between 1.8 - 2.5 ohms. (about $80 if it's shot)<br /><br />The thing also has to be adjusted. There is an indexing mark on the top of the choke mechanism. You loosen the three screws that hold it in place and rotate it clockwise to decrease choke.

 

[KCChris]

Re: HELP --- Carb. adjustment on 4.3 alpha one

Thanks for the reply. So do you think that the dark colored smoke indicates too much fuel?

 

[lorax]

Re: HELP --- Carb. adjustment on 4.3 alpha one

If it's black smoke, as opposed to blue or white then yes I'd bet it's the choke.<br />I removed the flame arrestor and started the boat. You could see that the choke was fully closed, the motor was belching black smoke and barely able to idle. If I shoved the choke valve open with a screw driver the smoke cleared up and the engine ran great.<br />It was pretty easy troubleshooting.

 

[KCChris]

Re: HELP --- Carb. adjustment on 4.3 alpha one

Thanks again lorax. I have been adjusting choke and fuel mix. I just can't seem to get it just where it needs to be. I have fuel about a 1/4 turn from being shut off. No smoke at all at higher RPM's(1500-2000). When I give it less choke I get less smoke. But I also get much higher RPM's. Just getting frustrated I guess. Any pointers on where they (Choke, fuel mix) should be).

 

[lorax]

Re: HELP --- Carb. adjustment on 4.3 alpha one

You said the idle speed increases when you open the choke. What happens when you back out the idle speed screw? Not the fuel mixture screw but the one that rest on the fast idle cam. It really sound to me like your choke is just misadjusted and/or it needs to be replaced.<br /><br />I don't know what the baseline adjustment is for your motor but 1/4 turn sounds pretty lean to me.<br /><br />What year is the motor?

 

[Northern Eclipse]

Re: HELP --- Carb. adjustment on 4.3 alpha one

KCChris what year is you boat motor ??? if its a later 80's model with Merccarb then your problem may be with the needle and seat there was a correction kit from merc, these Carbs are a japanese knock off and have been noted for poor idle rich running and flooding after shut down