Johnson 15 hp Cuts Out

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Well-known member
Aug 27, 2020
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Nature Coast of Florida
Y'all are prob'ly sick of hearing about my problems, but now I have a new one. My '83 Johnson 15 hp ran fine for quite a while, then one day I took off in it and it was great - for a couple 100 yards, then it quit. Had to row the little 12 ft back to the launch.

Long story much shorter, I did find water in the gas - quite a bit of it, so took care of that, all the way to the carb. No drain plug on float bowl, so pulled the carb and drained it....but problem was still there. I did double check float level while at it.

The motor had overheated badly when a plastic market bag wrapped around the lower unit in a canal and the coils were melted into their mounts. They tested good, but didn't ground well when replacing, so found a pair of used ones at a recycler. He had quite a few of them, but most tested open with an ohmmeter. I found 2 that tested good.

No difference, so replaced the trigger coil (??) with a new one - not used - I've heard they're very touchy beasties. Still no difference.

Haven't put it back in the water yet, but running it on the muff, it starts easily even after sitting for a couple of weeks. (pull start) Start it and it fires right up and idles fine, runs fine.....but after 3 or 4 minutes, it'll die. No fuss, just stops.

If I give it full choke, pull on it once, then open the choke and give it some throttle, it'll fire right has to be that exact sequence....but then it dies again after a few seconds. One or 2 more tries and it refuses to start. This has been on-going for a couple of months, so checked for water in the gas again and it's fine. No water.

Let it sit for a day and start over - it'll fire right up and go for a few minutes, then quit. Aaaarggh ! ! ! I'm tearing my hair out.
I called the old feller at the outboard recycle yard yesterday - he's got an outboard service business as well - and described my problem. He told me that those old Johnsons/Evinrudes had a problem with the filter in the fuel pump. They get a coating like a layer of varnish that you can't see, but will block flow of fuel. Carb cleaner will remove it.

Never heard of this. Have any of you here heard of it ?? Needless to say, I respect his opinion and will try it today.
So much for that. Took me a couple of days to get to it, but today were it. Pulled that screen and sho' nuff, hold it up to the light and it was about 3/4 blocked. Soaked it in Berryman's for a bit, then tried again and it were spotless, so re-installed it and tried again.

As before, full choke and motor started on 2nd pull and smoothed right out within seconds. Ran like a charm for a couple or 3 minutes, then quit. Aaaarrgh. Full choke for one pull, choke off and it started again, but raggedly and died within seconds. Wouldn't restart. Oh, when it did start the 2nd time, I pulled the choke out quickly and pushed back in and motor revved. Tried it a few times, then it died and stayed dead.

Someone on another forum suggested a coil breaking down as it heated up, but this sure acts like a fuel issue to me. It's a new fuel pump, double checked float level.....tearing my hair out.
LDUBS said:
Is it running out of fuel, like a collapsed fuel line from the tank?

And that folks is just about all I can offer when it comes to of my knowledge of outboard motor problems! :D

I tried squeezing the bulb - hard - while it was running. Made no difference - still died after a couple of minutes. I dunno; maybe that new trigger coil (??) breaking down when warmed up ?? If it was a spark coil, it'd keep on running on 1 cylinder. I think. Don't think there's a test for those trigger things and I'm not real crazy about spending another $60 - $70 on spec, just to see.
My little pea brain has been reasoning that it's running out of gas after a few minutes from the way it's acting. Yesterday, I started at square one. Again. All the fuel hoses are new, the squeeze bulb is new, I've checked the pickup tube in the tank and it appears solid.

I pulled the fuel line off the carb and stuck it in a jar, then started the motor. Nothing. ????? This is with a brand, spanking new fuel pump on the thing - not a rebuild kit. Checked all screws for tightness, then pulled the pump off to check the gasket. Tight and good.

OK, back to square 1(b). Squeeze the bulb hard and no leaks showing all the way to carburetor. Pulled the pickup tube out of the tank, plugged the end of it and switched the bulb and hoses around to pressurize that end of it and tried again. No leaks. I think it's safe to say that from pickup in tank to carb is tight and solid and compression is 120 which should give good pumping action, sooo.....??

I ordered a rebuild kit for that fuel pump yesterday and it should be here before the weekend. I am so gawddamned sick of fussing with this thing....anyone got some thermite they'll sell me cheap ??

I'm "pretty sure" that this whole sequence started with that grocery bag wrapped around the lower unit in the canal. When it quit, it was smoking hot.....enuf to melt the spark coils into the mounting bosses. Strange, tho' - after it cooled some, it started back up and brought me home. Then the fun started.
Have you pulled and checked the plugs? That may tell you a lot. It's a single carb motor so theoretically fuel delivery should be equal to each cylinder and both plugs should look very similar if the ignition system is working ok. If they differ then that leads to some more chasing but may help get you down the right path.

You could try bypassing all of the fuel paths to the carb. Not sure what the best way would be but maybe you could rig up something like one of those cheap primer bulb transfer pumps they sell at Harbor Freight straight to the carb fuel barb and put the other end down in a small gas jug. They are typically clear and you could then keep it pumping by hand and verify that fuel to the carb either fixes your problem or it persists, allowing you to check that off the list.
Sounds like the venting cap on your fuel tank may not be venting. The tank will develop a vacuum condition and the fuel pump can't pull against it. See if it'll run ok with the cap off. Happened to an old 6gal metal tank I had once.
Just a thought.
I FOUND IT ! ! !

Of all the damndest things that you'd never expect.

The kit for the fuel pump came in yesterday, so picked it up today and pulled the pump off the motor. Glanced down at it and immediately saw my problem. Bear in mind, this is a new pump and tho' it's been on there for months, it's only got - maybe - an hour or 2 of running time. I expected no problems there, so haven't looked for any.

The pulse port, where it mounts on the motor, was plugged solid. Almost didn't see it at 1st, cause it blended right in and it was recessed a bit. It looks like a thick, grainy black paste and it's pretty stiff consistency. No idea what it is - maybe carbon particles mixed with oil.....?? Never seen or heard of such a thing.

I used a dental pick to pull most of it out of there, then a thinned down Q-tip with carb cleaner to finish the job. For some reason, I have abysmal luck in working with these fuel pumps and avoid opening them up like the plague.

OK, optimistic all of a sudden, I put it back on and started 'er up. Ran as smooth and sweet as a kitten....and kept running this time. It'll get dumped in the canal tomorrow and we'll see what we shall see. What a relief. I hope.
A quick follow-up to show the "Luck o' Lars." The motor ran beautifully and at length on the muff Friday, so yesterday, Sunday, I gave a quick pull on the rope and it snorted at me, so good to go. Tank was almost empty, so pulled the 6.5 gal tank out of the 16 ft that has been sitting for a couple of months - with an inverted cup over the filler. It's got about 5 gal, so plenty of gas.

Down to the canal, launched it and started pulling. Stone, cold, Dead. Not a burp out of the fool thing. Scheiss ! ! ! I tried everything I could think of until my back gave out. Back home and started checking. Tank had a bunch of water in it that flooded the carb. HTH could it have that much water that soon ??

Today's project will be to clear all that out of there, which means pulling the carb - again - including the recoil starter and draining the float bowl, which doesn't have a drain - which means pulling the float bowl, too. Fine, but putting that starter back on is the job from hell. I'd like to catch up with the engineer who designed that thing and force feed it to him. Backwards.

Then we start over. Sure am tired of fussing with these things. I just wanna go fishing.
Those recoil starters can be little buggers. Hopefully you get it ironed out and can essentially never have to remove it again.
What you need to find out is if it is losing spark or fuel. Easy test, when it quits pull the cowl and give it a little snort of ether or carb cleaner. If it takes off, you know the ignition is fine and it's losing fuel.
Don't keep your fuel tank in the boat when your not using it. Keep it in a cool , dry place to avoid the rain and sun screwing up your gas. That **** is expensive!!

Sent from my SM-A526W using Tapatalk

GYPSY400 said:
Don't keep your fuel tank in the boat when your not using it. Keep it in a cool , dry place to avoid the rain and sun screwing up your gas. That [Censored] is expensive!!

Sent from my SM-A526W using Tapatalk

A cool, dry the Flarda Swamps in the summer...?? You bet. Water in the gas has been a repetitive, ongoing problem and I'd be half embarrassed to tell y'all what lengths I've been going to to get past the problem.
I'm having fits with the water in the motor. I did pull the carb and float bowl; I did purge the fuel lines all the way from tank to carb connection, including thru the fuel pump. It won't start. Won't even kick. I put the 1/2" drill motor on the flywheel nut and spun it and spun it. Nothing.

Pulled spark plugs and they're soaked - water soaked. Blew them dry, gave it some ether, spun it with the drill motor and it chugged a bit for a couple of revolutions, then nothing. Repeat several times. Pull the plugs again....soaked. How the hell do you dry these things out ?? It ran fine - for a few minutes - before it got that shot of water.

I'm at a loss with the gas tank, too, in both boats. Tighten the cap, close the vent, put a cup over the whole thing and in a couple or 3 weeks it's got a big shot of water in it again. Doesn't seem to make a difference if tank is full or nearly empty. Tearing my hair out here.
Fuel stabilizer? I religiously use Honda's Fuel Stabilizer (because I have a Honda outboard). It is supposed to address issues with ethanol laced gaso.

In my previous boat I had a 3 gallon portable tank. I didn't like the capacity. But one advantage of a small tank is with normal usage the fuel can be turned over fairly quickly.

Something I know little about and don't have is a fuel/water separator filter. Seems like a good idea, but as I say, I'm not one to ask.
Check your fuel lines. Sometimes a fuel line will develop an inner layer delamination and create a blockage in the line like a bubble. It may run a minute or two and then die when the bubble expands and blocks the line. Pumping the primer bulb would just make that bubble block the line even more.
Absolutely. I did that early on, found a bad one and replaced all of them with good, premium hose. This time round, as said above, I cleared the tank - thoroughly - then disconnected the fuel line at carburetor and put the end in a jar. Squeezed the bulb to get about a pint of gas and it showed no water. Flow is very good. I had already pulled the carb and removed the float bowl - there's no drain on it - to empty it.

Any water that's still in there has to be in the motor itself. Frustrating. I pulled the plugs and they were wet - water wet, not fuel wet. Blow them dry and pull a cloth between the electrode and ground to make sure, then re-install and crank. It'd gallop for a couple of revolutions, then settle down to just cranking.

Repeat - blow 'em dry, put 'em in, squirt some ether, gallop and crank. Pull the plugs and wet again. I dunno - went thru it 6 or 8 times and finally walked away while I still had some cool left.

Since that overheating episode in the canal, this thing has been one problem after another - it's nearly a new 40 yr old motor now. No end to it.