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25 hp Johnson Won't Accelerate

gogittumgogittum Nature CoastPosts: 2,694 Captain
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.

Replies

  • The Cat's EyeThe Cat's Eye Posts: 1,627 Captain
    i ran a 25 hp 1988 Rude all the way to 2017.  One good rebuild and another was faulty (Not by me). so i gave away the bad engine and kept the props if you are interested. One is S/S.

    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.
    Giimoozaabi
  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    Thanks for the thoughts.  I need to run it to see how the present prop does, then can make a choice from there, but yes, I'm interested.

    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.
  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    What makes it fun is that it runs perfectly on the muff.  Hafta load it all up, haul it down to the launch ramp and run it under load for the problem to show up.
  • The Cat's EyeThe Cat's Eye Posts: 1,627 Captain
    hummmm Low compression could be the problem then.
    Giimoozaabi
  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    hummmm Low compression could be the problem then.
    I checked compression before I bought it.  130 on both and he drove it in to meet me.  It was running but not really well.  I'll be going out in a few to start on the fuel supply.
  • conchydongconchydong Pompano BeachPosts: 11,059 AG
    Good luck gogittum. Hope it's something simple like the primer bulb collapsing.

    “Everyone behaves badly--given the chance.”
    ― Ernest Hemingway

  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    Thanks, Conchy.  A couple of people now, including Cats Eye have recommended starting at the beginning and the basics.  Today I did that - started at tank and checked and fussed with every single piece whether it looked good or not.  (they all looked good)  I hadn't done that because, as I say, it ran fine with the Suzuki.

    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.  
  • CaptjamesCaptjames Pompano BeachPosts: 197 Deckhand
    edited December 2021 #9
    it's too lean. turn the mixture screw out half a .  Hard starting and won't run with a load are both clear signs the fuel/air mixture is too lean on a 2 stroke. 
  • livebait1livebait1 west JaxPosts: 151 Deckhand
    you pull the jets when you went thru the carb?
  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    I ran it in the canal again this morning and same problem.  Tried opening the mixture 1/4 turn at a time until it was past 3 turns out and made no change.

    I pulled "everything" out of it when I went thru it and put in a full kit.

    Update coming in a minute or 3.
  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    Update....inconclusive.

    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 ???

    Automotive tire Automotive lighting Motor vehicle Gas Rim


    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.
  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    Update?
    New fuel pump will be here tomorrow.  Man, I hope that solves the problem. 
  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    I hate to even write this.  Put the new fuel pump on late yesterday and this morning I loaded the boat - tackle and all to go after some Crappie with - and headed for the canal that leads to the Withlacoochee.

    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.
  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    Something I completely forgot - suction or pressure leak ??  Boat was still loaded, so hooked back up just now and hauled it back to the river - it's only 1½ miles.

    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.
  • snookaffinitysnookaffinity Naples, FLPosts: 1,260 Officer
    edited December 2021 #17
    Sorry it didn't work out for you.
    "It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt." - Mark Twain
  • conchydongconchydong Pompano BeachPosts: 11,059 AG
    Dang Gitum I hope your luck changes. I keep thinking of this ditty when I read about your outboard problems.




    “Everyone behaves badly--given the chance.”
    ― Ernest Hemingway

  • The Cat's EyeThe Cat's Eye Posts: 1,627 Captain
     

    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.

     

    Giimoozaabi
  • Jstubby2Jstubby2 Lat -90 Long +90 👍Posts: 804 Officer
    Plugged jet, Ream out your with a small piece of wire. I had a similar issue with a 9.5 evenrude.  Also check that the crush cap covering the jet is not restricting the fuel flow . 

  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    Dang Gitum I hope your luck changes. I keep thinking of this ditty when I read about your outboard problems.




    Haha.....HeeHaw was my favorite for years.  Some a the girls....phew ! ! !  I still remember the words to that.  Seems like the story of my life.

     

     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'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.

    Jstubby2 said:
    Plugged jet, Ream out your with a small piece of wire. I had a similar issue with a 9.5 evenrude.  Also check that the crush cap covering the jet is not restricting the fuel flow . 

    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.
  • livebait1livebait1 west JaxPosts: 151 Deckhand
    Ever figure it out?
  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    No, been recovering from back surgery.  I'll be calling him soon.
  • snookaffinitysnookaffinity Naples, FLPosts: 1,260 Officer
    Wish you a speedy recovery.
    "It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt." - Mark Twain
  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    Wish you a speedy recovery.
    Thanks.  Now the left knee has gone phooey and giving me fits.  No end to it.
  • Jstubby2Jstubby2 Lat -90 Long +90 👍Posts: 804 Officer
    Hang in there Gittum, this getting old crap ain't for sissies 
  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    Man, you ain't said poop.  Any ideas on how I can stop the process ??  I'm getting tired of it.
  • conchydongconchydong Pompano BeachPosts: 11,059 AG
    gogittum said:
    Man, you ain't said poop.  Any ideas on how I can stop the process ??  I'm getting tired of it.
    There’s only one way and the ending ain’t too pretty.

    “Everyone behaves badly--given the chance.”
    ― Ernest Hemingway

  • chaser48chaser48 San Mateo Fla.Posts: 290 Deckhand
    As we git older we pay for our " hold my beer days"  I feel your pain
  • KlingerKlinger Posts: 2,124 Captain
    As a 74 year old that has had a hip replaced, a shoulder replaced, the Prostate removed, a heart bypass, and a heart valve replaced, I feel your pain.  Just thankful I can still spend time with friends and family on the water and in the woods.  Don't give up!
    In my many years, I have come to a conclusion that one useless man is a shame,two is a law firm, and three or more is a congress.-- John Adams
  • gogittumgogittum Nature CoastPosts: 2,694 Captain
    Haha.....yah, there's been an awful lot of hold my beer days and not "too" many regrets.  It's been a very active and varied life and a great go-round......and not over yet.
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