Outboard Motor Problem

[ttitan27]

I have a 1997 Johnson 25 hp motor that starts and runs great with one exception. When left on idle for more than a few minutes, it struggles to get back up to full power. The engine revs and sputters and will eventually start running smooth again. I had heard it could be a problem with the carb "loading" and that a good carb clean or rebuild may fix the problem.

This weekend I removed the carb and with rebuild kit, I cleaned and rebuilt the carb. Took it to the lake and the exact same thing occured.

Any suggestions of the cause? Fuel pump? Plugs?

Any advice is appreciated.

[SAMBOLIE]

Sounds like plugs. How old are they?

[Paincave]

Bad/old gas maybe?

[ttitan27]

Originally Posted by Paincave

Bad/old gas maybe?

Definitely not this as I started with a fresh tank this fishing season and have only added as needed.

[ttitan27]

Originally Posted by SAMBOLIE

Sounds like plugs. How old are they?

Not sure, I bought the boat three years ago and it is the plugs that were in place at that time.

[Paincave]

Originally Posted by ttitan27

Definitely not this as I started with a fresh tank this fishing season and have only added as needed.

That's good, yea, then I'd try the plugs next. Just a process of elimination, start cheap and go from there.

[Halli]

Take it to this Fellow here http://www.oldoutboardbarn.com/

[ttitan27]

Originally Posted by Halli

Take it to this Fellow here http://www.oldoutboardbarn.com/

Yes I was hoping TK might have a suggestion or two.

[wormdunker]

My engine sort of had the same issue there for awhile, and I am trying to recall what all I did to finally get it right, but as best as I can remember, it seemed to boil down to a float needle not seating properly. Did you replace that needle and seat with the rebuild kit? I also remember that I had a small tear in the diaphragm, which could have been the problem too. I replaced the needles, gaskets in all 3 carbs, that diaphragm in one of them, and the problem was cured, although I don't know which was the trick that did it. Also, if you have been running 10% ethanol fuel, it is a good probability that your floats could be saturated and heavy, not allowing the needle to seat properly. I'm just a shade tree mechanic, so take this advice with a grain of salt. Good luck, and let us know if you find out what the problem is.

[wormdunker]

Oh, yeah, and I would definitely change those plugs if they are 3 years old. Try NGK plugs, I think that they are a superior plug for outboards, motorcycles, and such.. Most any parts store can cross reference them with what you have now.

[creekcrappie]

Yes I would highly recomend taking it to tk.

[ttitan27]

Originally Posted by wormdunker

My engine sort of had the same issue there for awhile, and I am trying to recall what all I did to finally get it right, but as best as I can remember, it seemed to boil down to a float needle not seating properly. Did you replace that needle and seat with the rebuild kit? I also remember that I had a small tear in the diaphragm, which could have been the problem too. I replaced the needles, gaskets in all 3 carbs, that diaphragm in one of them, and the problem was cured, although I don't know which was the trick that did it. Also, if you have been running 10% ethanol fuel, it is a good probability that your floats could be saturated and heavy, not allowing the needle to seat properly. I'm just a shade tree mechanic, so take this advice with a grain of salt. Good luck, and let us know if you find out what the problem is.

Yes, I did replace the needle and seat and gaskets. Also replaced the float as well. I have only run non ethanol gas in the engine since I purchased the boat used 3 years ago but I have no idea what was used before that. I'm fortunate there is a non ethanol gas station a mile from my house.

I pulled the plugs and they looked incredibly old and worn. The gaps were at .050 which I attributed to erosion. I replaced with new plugs (NGK) gapped at .030 (man. recommendation). I haven't had a chance to see if this will solve the problem but should be able to give it a run on Friday morning. Thanks for the suggestions.

[wormdunker]

Also thought of something else. That float tab must be set to where the floats are parallel to the carb body. If set wrong, it can either allow too much or too little fuel to pass through, causing either loading up or starvation.

[ttitan27]

Originally Posted by wormdunker

Also thought of something else. That float tab must be set to where the floats are parallel to the carb body. If set wrong, it can either allow too much or too little fuel to pass through, causing either loading up or starvation.

New plugs didn't solve the issue either.

I'm afraid I don't follow you on this suggestion wormdunker. I don't think I am knowledgeable enough to understand. Could you please try to explain this a little more? Also is their any possibility that the fuel pump could have a problem?

[wormdunker]

Sorry, I should have gone into a little more detail than that. About the fuel pump, I don't know too much. If it has a diaphragm in the fuel pump, that would definitely be worth a looksee for any tears or holes, etc. I know ethanol fuel can weaken them if they are made of certain materials. Also if there are check valves at the points where the fuel line enters and exits the pump, they can go bad and cause fuel to not be delivered properly-I think- as I say, I don't know too much about the pumps and how they work. I have, though, had some experience with the float tabs and float levels in both outboards I have had, and some motorcycles. I think it would definitely be worth looking at. I hope the carb isn't too much a pain to get off. On the float, there is (I guess there is on a Johnson 25 float) there should be a little "tab" that contacts the needle to basically, I guess you could say, allow the needle to open (float drops down) and allow fuel to flow, or close into the seat to shut off the flow of fuel as the carb bowl fills and the float rises. That tab needs to be adjusted just right. With the carb off and upside down on your work bench, (or kitchen table), with the bowl removed, the needle will naturally be in the closed or shut off position, seated in the needle seat. Slowly lower the float until the tab JUST touches the needle. Don't let go of it, at this point, the float should be perfectly parallel, or level you might say, to the carb body. If it is sticking up on the end opposite the tab, then you need to carefully, with a pair of needle nose pliers, bend that tab up slightly. If the float is slumping down, unlevel at the point that it touches the needle (which, if I am thinking right, would be the "too much fuel" scenario) then the tab needs to be bent the other way until the float is perfectly parallel with the flat surface of the carb body when it just touches the needle. That's the only way I know to explain it. If all this is as clear as mud, you can google some of these terms and maybe find some pictures of the procedure. It's not hard, really, although I probably didn't explain it too well. I hope this helps, and forgive me TK if this kind of stuff is not welcome in the "fishing" section of the forum, or maybe not cool to post at all ? Hope not. I haven't been on board too long, and may not know protocol well. Thanks, and good luck with it. If you want to look there are some good mechanical forums out there that can be really helpful, like iboats.com and Thehulltruth.com are a couple that I can think of.