Midrange Stumble

Was thinking of splashing the Elgin with the 6HP Johnny, but it's not accelerating as smooth as it should. As you roll the throttle there is a point where it stops accelerating, but if I take her to WOT after a few seconds it "catches" and seems good and strong. Didn't replace a whole lot of parts, but I did test and adj everything I could and think it's all set right. So sounds like carb, right? I cleaned it, but maybe I missed something. Guess I'll clean it again if nobody else has a better idea.

Something else odd is it doesn't seem like fiddling with the low speed adjustment does much. It's been sitting a long time, I want to think maybe running it will help, but that's probably just wishful thinking.

Not saying that you would do this but I have seen people remove the carb/carbs, clean them thoroughly and then hook the same gas tank right back to the cleaned carbs........ Of course within a minute or two they are right back to where they started......

You are so right! That was me a couple summers ago. The boat I bought which was supposedly ready to go with a full tank of fuel, having been used days before was kind of a turd. The tank was full of little gray boogers, I guess from ethanol? Think the seller put new gas in with the old. Anyhow dumbass me had to clean that carb several times before figuring it out. Something else I figured out. ALWAYS put an inline filter on it. Which I did with this one, so I don't think I likely sucked anything in unless it got sucked in the carb mouth.

Is compression good ? If so then how good are spark plugs ? Right ones ? If all of this is good then flush out the tank and check pickup tube in the tank. Clean out the fuel line, check for internal clogs, is the fuel line one if those crappy gray lines ? Once all that is corrected, did you use a rebuild kit or just a quick clean for the carb ? I start with the easy stuff first, check and clean properly everything. If it still acts up then you will need a deeper dig and others will be much better at guiding you thru that. However, if you go that way, you already know the entire fuel system is clean as are plugs good and properly tapped and compression is good.

You didn't mention a year are we dealing with a points or electronic ignition?

Compression is very good. Plugs I simply cleaned and put back in. Guess they might not be the right ones. Thanks for the thought. I'll try to figure that out. With so many plugs being superceded by others on these old motors it's pretty much just a crapshoot though isn't it? Take a guess and hope you're close.

I'm using my trusty test tank which I use on everything and run in my Mirro when I go out. As far as I know it should be clean and in good shape. Lines are the old style black ones. I've had it on several motors without issues. I also put SF in the gas late in the year religiously to avoid ethanol goobers.

It's a 75 with points and all that happy crappy. I took great care timing it and think I nailed it. Also synced the advance plate with the throttle. As for parts the only replacement was one dodgy looking coil which I swapped for a known good one.

If new plugs don't help I'd go back to the carb.

Thanks for posting that. Are those current part nos. or original part nos?

LaqueRatt said:

Thanks for posting that. Are those current part nos. or original part nos?

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Not sure honestly I pulled it of marineengine.com I've had good luck with the company in the past and their website is easy to find parts.

Plugs that are in it look new and are Champion JC6. Not on the list. OK to use?

I'm assuming you meant j6c which is a colder running plug than the j8c that was on the list I posted for your motor. I would try the hotter plug (j8c) and report back your findings.