1999 115/80 Johnson won't go WOT

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I have a 1999 115/80 Johnson Jet. It ran fine this winter/spring but when I took it out yesterday after sitting for a month it wouldn't get above 4,400 rpms. I replaced the external and internal fuel filter and no change.

I had a friend go out with me this afternoon and had him pump the bulb while running. It jumped right up to 5,200 and held for a moment then dropped back down to 4,400.

I am sure that it has original lines and fuel pump. I plan to replace the lines and bulb tonight, if that doesn't do it, does it need a new fuel pump?
 

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Re: 1999 115/80 Johnson won't go WOT

So I changed the lines and the same symptoms persist, it will jump back up to 5,200 if the bulb is pumped. Does this sound like the fuel pump? Am I on the right track?

I have read the stuff over at max rules dot com and it looks like the rebuild isn't too difficult. I just want to make sure I don't order the kit and pul everything apart and figure out it is something entirely different.
 

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Re: 1999 115/80 Johnson won't go WOT

So I took the fuel pump off and tested it with the guidelines in the factory manual. It was fine.

I soaked the pulse limiter overnight in carb cleaner. Put it back together and it ran a little better, up to 4,700 RPMs the following day. Then it dipped back down to 4,400.

I bought the carb kits with floats and pulled those off. All 4 bowls were warped, but the guy I bought this from two years ago said he never touched anything or took it in for service so that means they warped from the factory. Guess the theory that overtightening is the culprit needs a few more case studies to stand.

It does explain the sloppy mess of fermented premix in the lower cowling. At least the motor itself was engineered with limited external ignition sources. I think plastic parts containing a solvent adjacent to a heat source was bad engineering to begin with.

As near as I could tell, there weren't any obstructions. I didn't soak the carbs but did soak the high and intermediate jets and bowl drain plugs.

For some reason last year when I replaced the plugs I ended up with 77s instead of 78s. I changed those today as well.

So I am waiting on 4 new bowls, a short assembly and a decarb to hopefully close out this thread.

Whats the deal with the underwhelming response? It seems like if I posted about a propeller pitch problem on a 77 25 horse I would've received more advice. Oh well.

Maybe someone in the future will read this and go right to the horribly designed carburators . . . then again, us low drafters are a scarce bunch.
 
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Re: 1999 115/80 Johnson won't go WOT

looks like you have a good idea whats wrong. lack of rpm is lack of hp and you tested the bulb so it looks like a lack of fuel on at lest one of the carbs when on the high rpm jets. the normal advise is to replace all fuel hoses as they degrade, rebuild the carbs and check high rpm needles for blockages, check and change the plugs, compression test and rebuild the fuel pump ..........looks like you are doing well so far lol. i agree with you that plastic under the cowling seems like a bad idea but thats the way manufactors are going these days so it can only get better or worse a bit like fuel injection in years to come it will be the preferred material once they work out the kinks in it. hope you get it sorted soon
 

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Re: 1999 115/80 Johnson won't go WOT

So the top end of the RPM range along with the hole shot and all around torque is vastly improved.

Unfortunately, I cannot get the idle dialed in. I have the 60 V4 looper and am contemplating taking it to a mechanic for the link + sync. The factory manual makes mention of several expensive tools needed to perform this "routine maintenance" so I am at a loss whether to purchase them or take it in.

I followed the instructions on setting the idle adjustment and backed out the needle 4.5 turns from the "bottoming out." I adjusted each carburator another 3 revolutions beyond that but never had the rough running/sneezing cease. I was fearful that I would back the needle all the way out and be stuck with a problem so I decided to stop. It starts, runs rough for about 40 seconds, then dies. Of note, the small crankcase venitlation hose that fits into the air cleaner (I assume that is what it is) was shooting out a puff of blue smoke when it would die.

So if I start it, I immediately set the throttle to 1,500 rpm and it runs fine. I was quite pleased with the performance today and even decided that I will not get a new engine this spring. If I can get this idle dialed in I will be a happy boater.
 
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