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25 hp Johnson Won't Accelerate
Going thru my new-to-me 1993 Johnson 25 hp 2 smoke and thought I had it all ready to go. Rebuilt the carburetor, which was simple enuf but ran into a question between a couple of YouTubes. Most say to turn the float bowl upside down and make sure the float is exactly parallel with the top edge of the float bowl....which is what I've always understood to be right and is what I did.
Some say to hold it the other way, with the float hanging down and measure from edge of the bowl to lowest edge of float and it should be...uh...1 1/8", I think. I'm having problems which I'll explain in a bit.
It's a bit of a long story, but briefly, I felt the fuel pump wasn't putting out, so put a kit into it, too. Not rocket science, but the way it's set up it does take care and precision on assembly.
Put the whole thing together, connected the tank, full of fresh 50:1 and started it up....tried to. This motor doesn't have a choke, just a fast idle control on the single lever control. No choke plate in the carb. It would crank hard but not fire. Fast idle didn't help. Finally, I held the key in one hand and when I started cranking it, I put the other hand over the carb inlet. Boom - that thing was running instantly....then died.
Playing patty-cake with my "choke," I was able to keep it running until after a minute or so it smoothed out and kept going on its' own. Then adjusted mixture till it smoothed out.....sort of. It still will go rrrrrrpoprrrrrpoprrrrr....etc.
Yesterday I launched it in the river and started out. Fine, but when I got clear of the no wake zone and gave it gas, it started to rev and go, then died. Restart and same thing. It'll give a brief acceleration, then die back to idle.
OK, I "think" the float level should be good, so pulled the output tube off the fuel pump and put a short piece of tubing from the outlet into a jar. When I started it, it just gave splatters of fuel, so figured that's why it wouldn't accelerate.
I pulled the fuel pump back off and dis-assembled it, then watched YouTubes for a review and went back out to re-assemble it. It's a bit fussy to put together but I believe I've got it right. Started the motor and all was the same as before.
Fuel pressure gauge at O'Reilly's was already rented out, so came home, started it up and put my digital tire pressure gauge on the schrader fitting on the thingie beside the carburetor and tee'd into the fuel line. There was enuf pressure to activate the gauge and light it up but no pressure registered. It has new batteries.
Checked all the hoses, connections....all look good, clean, tight and solid....?? I'm baffled. Why can't I get that fuel pump to put out ?? There's a small tube comes from a fitting high on the rear of the side plate on port side that just goes down under the powerhead and ends. Not connected to anything. Is that just a vent ??
Any Ideas will be very welcome - I want to go out of Crystal River and chase Grouper while they're still open.
Some say to hold it the other way, with the float hanging down and measure from edge of the bowl to lowest edge of float and it should be...uh...1 1/8", I think. I'm having problems which I'll explain in a bit.
It's a bit of a long story, but briefly, I felt the fuel pump wasn't putting out, so put a kit into it, too. Not rocket science, but the way it's set up it does take care and precision on assembly.
Put the whole thing together, connected the tank, full of fresh 50:1 and started it up....tried to. This motor doesn't have a choke, just a fast idle control on the single lever control. No choke plate in the carb. It would crank hard but not fire. Fast idle didn't help. Finally, I held the key in one hand and when I started cranking it, I put the other hand over the carb inlet. Boom - that thing was running instantly....then died.
Playing patty-cake with my "choke," I was able to keep it running until after a minute or so it smoothed out and kept going on its' own. Then adjusted mixture till it smoothed out.....sort of. It still will go rrrrrrpoprrrrrpoprrrrr....etc.
Yesterday I launched it in the river and started out. Fine, but when I got clear of the no wake zone and gave it gas, it started to rev and go, then died. Restart and same thing. It'll give a brief acceleration, then die back to idle.
OK, I "think" the float level should be good, so pulled the output tube off the fuel pump and put a short piece of tubing from the outlet into a jar. When I started it, it just gave splatters of fuel, so figured that's why it wouldn't accelerate.
I pulled the fuel pump back off and dis-assembled it, then watched YouTubes for a review and went back out to re-assemble it. It's a bit fussy to put together but I believe I've got it right. Started the motor and all was the same as before.
Fuel pressure gauge at O'Reilly's was already rented out, so came home, started it up and put my digital tire pressure gauge on the schrader fitting on the thingie beside the carburetor and tee'd into the fuel line. There was enuf pressure to activate the gauge and light it up but no pressure registered. It has new batteries.
Checked all the hoses, connections....all look good, clean, tight and solid....?? I'm baffled. Why can't I get that fuel pump to put out ?? There's a small tube comes from a fitting high on the rear of the side plate on port side that just goes down under the powerhead and ends. Not connected to anything. Is that just a vent ??
Any Ideas will be very welcome - I want to go out of Crystal River and chase Grouper while they're still open.
Replies
Your problem might not be the carb at all. I would first check to see if the compression in both cylinders is up to par and even. Secondly, i would try a different fuel line and gas tank. I once had similar problems as you are experiencing. One was low compression. Others were a faulty fitting on a fuel tank and a third was a bad fitting on a fuel line restricting fuel flow. Also check and make sure the bulb on the fuel line is staying firm. if it gets soft you have a air leak someiwhere in the fuel line system. I would also change out the fuel line on the engine as well.
The tank, fuel lines and connector are the same ones that the Suzuki ran fine on, but your points are well taken and I'll check all that out. Could be something as simple as a piece of rubber caught in the hose to motor connector.....but I doubt it. We'll see. Cpmpression is 130 on both cylinders.
“Everyone behaves badly--given the chance.”
― Ernest Hemingway
Long story a bit shorter, when I pulled the output from fuel pump to carb and put an extension in a jar and cranked it, I got a steady, solid stream of gas from a ¼" tube this time, where it just spluttered before. It started more easily and smoothed out more quickly, too. Too late by then for today - it's going back in canal/river tomorrow.
Not counting chickens just yet, but feeling more optimistic.
I pulled "everything" out of it when I went thru it and put in a full kit.
Update coming in a minute or 3.
Took it for a run on the canal this morning and same thing. It'll give a quick growl, then die off. It was a little easier to start and keep running as it warmed up, but no real improvement. Yesterday, I went thru the supply fittings and tubing and all look good, so this time when I got home, I pulled the output off'n the fuel pump, put a piece of tubing on it and led it to a jar. It pumped gas into that jar lickety-split......after I'd squeeze bulbed gas to it. About 2" of gas into a pint jar in ~30 seconds.
Not fuel pump. gotta be carburetor, so pulled the starter and then the carb. I was verrry careful to keep the carb upright and glad I was. I held it in running position and removed the bowl screws from below, then carefully eased the bowl straight down. It was empty. EMPTY ! ! ! WTH ?? HTH ???
I checked the float needle and seat and all is well there. Float was exactly parallel to bowl edge when held upside down.
It's only 1/4" tubing and there's a T in there, so maybe a restriction ?? Next, I pulled the supply line off the carb and pushed a piece of clear tubing over it and led that to a jar. It did pump a lot of gas - about 1/2" in 15 seconds, but it was frothy. Once it got going good it did much better but still a lot of bubbles in it. I darkened this picture quite a bit to show it better.
Only place I hadn't checked was the tube that comes from the connector fitting on side of motor and under/behind the carb to the fuel pump, so did that and found that it had been zip tied on but the zip tie was behind the barbs on soft hose. Maybe a small suction leak ?? Fixed that.
I dunno. Even with bubbles, seems like that should be lots of gas to make it go, but apparently not. I'll order a new fuel pump in the morning.
Test run on the muff, the motor did start more easily and tuned to a nice idle easily. We Fat......I thought.
Hit the water and - no change. It idles fine, push the throttle forward and it surges forward......then craps out after one or 2 seconds. Leave the throttle be and it'll run raggedly at low speed, then once in a while it'll surge forward for a second.
When I pulled the carb off the other day, the float bowl was empty. Checked fuel flow and it seemed fine. Pulled fuel line off carb and had good flow - before the new pump. Float level was right on spec.
I dunno. Go sit out there and stare at it and scratch my head, I guess.
This time when I started out, I squeezed the bulb to make sure it stayed hard. When I started to accelerate, I squeezed hard, trying to force gas up into the carburetor. There was no evidence of gas leaks anywhere.
Made no difference. Same problem as before. To my eyes now, the problem's gotta be in the carb. I'm not up for it today.....maybe tomorrow.
“Everyone behaves badly--given the chance.”
― Ernest Hemingway
i use to rebuild many different types of carbs. I had a 1960 Corvette dragster that had duel 4 barrels. i rebuilt those Rodchester Quadrojets successfully. A few years later i bought my first fiberglass boat and it came with one Quardrojet that gave me problems that drove me cralzy until I bought a Quardrojet manual. The problem was a vacumn leak on the ends of the butterfly shaft. This caused the same problem as you describe with your 25 hp, This problem was not repairable since the shaft had worn out the brass bushings in the top housing of the four barrel. These bushings cannot be replaced.
I finally got my hands on a brand new marine Quardrojet that a repair shop tossed out due to salt water intrusion. They gave it to me for nothing. I rebuilt it and my small block Chevy V8 ran like new. To test for a vacumn leak on any carb is very simple. While the engine is idling you take a small soft brush and dip it in a cup of fuel. Then you paint the exterior of the carb on shafts and joints with fuel. If the engine RPM increases you have a vacumn leak that may not be fixable. I think this would be rare on a simple one barel carb, but I suppose it could be possible.
You might need to buy a new carb.
I'll check it, but when I pulled the carb, as I said, the float bowl was empty. If it doesn't have any gas, it can't accelerate - that's why I tried squeezing the bulb when running this last time. Today's a new day - we'll get back after it a bit later.
P.S. When I was shopping for my '67 Stingray 427 in '69, I test drove a '62 with dual 4 barrels. Thing was a kick in the pants to drive, but common sense prevailed.
Yah, when I put the kit in the carb, I soaked it in Berryman's overnight - with everything apart, including jet, then ran a soft copper wire thru all orifices and blew it out with air.
I was very careful with crush caps. Ground the end of a slightly smaller bolt flat to make a separate driver for each one and was very gentle. They're flat - not dimpled down, so I think I'm OK there.
I even pulled the needle/seat brass fitting when I opened it up this last time and measured from the gasket seating surface to the end of the fitting. Then measured from where the fitting seated in the carb to the bottom where the gas comes in. It wasn't much - only 0.2" of space (the gasket would add a bit to that, too) but that would be enuf to let gas into float bowl.
I'll tinker with it a bit over the weekend, but I'm about blown on this thing. I wanna go fishing, ****. A shop in Crystal River (different forum) has offered to take a look at it for me, so it'll land on their doorstep early next week.
Thanks all, for the thoughts and comments. It's appreciated.
“Everyone behaves badly--given the chance.”
― Ernest Hemingway