adjusting carb to run smother on 78 200hp Evinrude

[70wellcraftV20]

Just wanted to know how to adjust the carbs<br />because I don't see any mixture screw on the carbs<br />which I think it is running a bit lean because it idles a bit rough and sometime sneezes and cuts out.<br />just trying to make it run better<br />thanks for any help

 

[JB]

Re: adjusting carb to run smother on 78 200hp Evinrude

Howdy, Wellcraft.<br /><br />I suggest that you get a Service Manual first.<br /><br />Then give the carbs a thorough cleaning and finish off with a "by the book" link 'n' synch adjustment procedure.<br /><br />That should have her humming again.<br /><br />Good luck.

 

[Dhadley]

Re: adjusting carb to run smother on 78 200hp Evinrude

Ditto. And make sure you have the correct spark plugs and FRESH 87 octane fuel. 6 week old fuel is not fresh, btw.<br /><br />Its true that some of the older motors MAY have to be rejetted. They were produced and calibrated for the fuel available at the time. 1978 fuel is long gone. The first step is to follow JB's advise and follow up with a good decarb job. Then go from there.<br /><br />If its any encouragement, I have an older 150 crossflow that idles at 500, or less, in gear perfectly and has never been rejetted.

 

[moderator1]

Re: adjusting carb to run smother on 78 200hp Evinrude

The boys at Mar-Fab are recommending an increase of 1 to 2 sizes for that vintage 200 on the mains.<br />But, as Dhadley says, some are just fine, and may need a good cleaning and some fresh 87...

 

[snagroms]

Re: adjusting carb to run smother on 78 200hp Evinrude

Just began working on a 1978 175 evinrude and found the OEM manual to be my best friend. Got mine from outboardwizard and saw some on ebay. The manual covers 175/200/235's.<br /><br />Per the manual you will not find mixture adjusting screws. Its all in a clean and syncronized fuel to ignition setup. Follow JB and Dhadley's advice after you get the book. Then work from there!

 

[marinemech1]

Re: adjusting carb to run smother on 78 200hp Evinrude

make sure motor is at operating temp - both heads<br />sync and link also critical for smooth idle<br />also don't try to set up on a flusher put it in the water not tied to a dock

 

[70wellcraftV20]

Re: adjusting carb to run smother on 78 200hp Evinrude

I took it out tonight it runs great at above idel speeds<br />but at the lower rpms it has a bit of a cough<br />and if I lower it to around 500rpms that same cough or sneeze will cause it to cut out. I can restart it with a bit more throttle. but I can't seem to keep it running smooth at the low idle speed<br /> <br />the carbs were rebuilt last year and I have not run it much because I had a timing advance issue<br />where the timing base was a bit sticky and was not advanceing at past 2500rpms so it took me a while to figure that one out.<br /> <br />but the gas is about 6 months old.<br />could this just be a carb sink problem? or old gas?<br /> <br />my manual says that a rough idle could be a bad diode in the powerpack?<br /> <br />thanks for your help

 

[Basscat 1]

Re: adjusting carb to run smother on 78 200hp Evinrude

I would change gas before I done anything else. It may be your only problem.

 

[70wellcraftV20]

Re: adjusting carb to run smother on 78 200hp Evinrude

also I read on the forum that it could be the reed valves not sealing off?<br />but I will try the gas first.<br />thanks

 

[Dhadley]

Re: adjusting carb to run smother on 78 200hp Evinrude

A few things to keep in mind -- 6 month old gas can be fatal to pistons. Just because your carbs were cleaned last year doesnt mean they're clean now. Especially since "I have not run it much". Motors that are run every week are way less likely to have gummed up carbs than those that sit. <br /><br />Your motor should idle at 650 or so in gear. Get it running perfect there and then try for less. It may not be possible if your motor is sitting deeper in the water at idle (backpressure) than mine. 650 is fine.

 

[70wellcraftV20]

Re: adjusting carb to run smother on 78 200hp Evinrude

also what does decarbining involve?<br />will that make it idle smother?

 

[Dhadley]

Re: adjusting carb to run smother on 78 200hp Evinrude

If your rings are starting to stick (from coking) it sure will. At any rate it cant hurt IF you follow the instructions on the can very closely. I've always used Engine Tuner that you get from your local Evin/John dealer.

 

[70wellcraftV20]

Re: adjusting carb to run smother on 78 200hp Evinrude

is that just something you put in your gas?

 

[Dhadley]

Re: adjusting carb to run smother on 78 200hp Evinrude

Engine Tuner comes in 2 forms. Both in a spray can but one has a small clear hose and one has a small straw like deal for spraying. You dont want the one with the clear hose. Thats for motors wth a primer, not a choke. <br /><br />Youll get the spray version with the "straw" and start the motor. Once its warmed up youll spray Tuner down each carb throat. Once you get some in each throat youll spray enough in to choke the motor down or nearly down. Shut the motor off and let it sit in there awhile. We usually let it sit about 2 hours. Then crank it up and let it run until you are sure its all out. We usually like to use about a third of a can. <br /><br />If the compression comes up and/or it idles better, we may do it again after the next trip. The trick is to run it enough to get it all out. You dont want it sitting in there for extended lengths of time. Youll probably want to change the plugs afterwards.

 

[70wellcraftV20]

Re: adjusting carb to run smother on 78 200hp Evinrude

tried new gas that helped a bunch but I can't get it to idle down below 900rpms I have the throttle all the way backed up but it still wont drop down<br />with the new gas the hickup is gone after a minute of warming up<br />but the idle might drop more once I get in the water because I was doing all this with the water flush hooked up in the driveway<br />I figure with the extra backpressure of being in the water might bring down the idle?<br />is there any thing else I can do to bring down the idle<br />I have loosened the linkage like the manual says. to get them all in sink but that did change anything.<br /><br />thanks

 

[Basscat 1]

Re: adjusting carb to run smother on 78 200hp Evinrude

The idle will be higher in the driveway. You are exactly right about the backpressure.<br />Wait until you get in the lake to check the idle.<br />To set the idle on mine, it has to be running in the water, (tied off to dock) in gear at 650.