Johnson 1995 25 HP Fuel Problems

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LS1967gto

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I have a 25 hp 1995 Johnson model # J25REO and am having fuel problems with it. It runs fine at idle and about quarter throttle but if you give it any more gas it acts like it starving for fuel. I have replaced all gas lines from the tank also replaced primer bulb and put on new fuel pump plus a new power pack. I have also used a different tank and fuel lines with no change. It seems to be getting plenty of fuel to carb but it?s not getting enough to motor. The carb has been soaked and cleaned and new carb kit put on. When it acts up if you pump the primer bulb it will run better but not at full speed. Any ideas on what could be the problem.
 

racerone

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Compression test done ?----Reed valves checked ?-----Water pump maintained ?----High speed jet was removed from the bottom of the float bowl for cleaning ?
 

boobie

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You could have a piece of crap underneath the seat for the needle in the carb and the primer bulb tries to over ride it.
 

Ppopps

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Amazingly I have the same problem with the same motor. I too have gone through carbs, fuel line, and pump. On mine it chokes out only at full throttle but squirt a little mixed fuel in the carb throat with a windex bottle and it picks right up, so I know it's fuel supply related. Boogie - what do you mean by needle and seat, the float needle and its seat? I also dont see a high speed jet in the float bowl as raceron suggested to check, all I see is the long tube with a needle somewhat jammed inside that doesn't slide or move at all. I blew out all the passages I could find. Could someone explain the carb better to me and what to dismantle for cleaning and how?
 

Ppopps

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Thanks racerone, I'll dismantle that but thought it was just a fuel bypass for the choke/starting primer. As I've blown air through it and think it's not the issue, can I ask how you would debug whether my problem, remember motor picks up if I squirt fuel into carb throat at higher rpm, is carb or fuel pump related? Is it reasonable to think that as squeezing the primer ball doesn't help that it isn't pump or can the pump diaphragm or something internal fail such that the primer ball can't push fuel all the way to carb? I dismantled and reassembled pump, all looked good to me. I'm missing something clearly.
 
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racerone

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If squeezing the bulb does not help / change the way the motor runs , you do not have a fuel pump problem---Perhaps there is an issue with the thin rod that goes to the back of the motor.----Many folks adjust that stop because it looks wrong to them.---That results in opening the throttle too early and the motor does not like that.----Make sure item 22 is clean( very clean ) and that item 20 is in place.
 
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Ppopps

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I haven't adjusted anything on the rods or stops and it ran perfectly until exhibiting it's current problem the day after a very bumpy ride back (in big waves) to the boat ramp. I'm showing pictures here of my carb ripped down. See the concentric tubes (don't know what they're called) and how the inner one is spring tight against the side of the outer one, is that normal or should it be centered? The inner one shouldn't slide should it? It's like it's bow shaped or something and jammed in place and rides tight to one side of the outer one at the bottom where it meets the high speed jet you tell me to IMG_0065.JPG IMG_0062.JPG clean. Does it all look and sound normal to you? Thanks for all the help.
 

racerone

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All looks like the way it left the factory.------Nothing appears wrong.----Remove seat for the float valve and blow that passage way out with some air.
 

Ppopps

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Racerone you got me thinking, maybe it's some crud stuck in the fuel line that feeds the high speed jet at the bottom given the symptoms?

That would explain only dying at high RPM and no change with primer ball squeeze and perfect looking carb, no?
 

Ppopps

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Racerone, I think I see now that my last question likely makes no sense, the hose running into the port close to the high speed port is not supplying fuel at all is it, it's the suction point for the plunger to draw fuel from the float bowl?

You now have me wondering about the small rod to the back you talked of, and that stopper. Is this it in the picture that I'm pointing to with a screw driver? Does the stopper look right to you and how do you adjust it properly? The last day this boat ran well was a really choppy day on the water so although the stop looks tight I suppose it's possible it moved?

 

racerone

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With the throttle at idle there is usually a gap at the stopper.---If the adjustable stop is tight it may be opening the throttle too soon.
 

Ppopps

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I understand the gap and stop and am sure it is fine and has never moved. I've just come back from a water test, nothing I did helped at all. So far I cleaned the carb within an inch of it's life (am sure it's not carb) and checked the filter screen on the fuel pump. I didn't think that squeezing the primer ball changed behavior but now I'm not so sure. The motor runs flawless at idle, even in neutral at high rev, but put it in gear and try to go and it surges, kind of oscillates if you know what I mean, almost stalling, then picking up, then almost stalling and inevitably does. Could that be a weak fuel pump? If I squeeze the primer ball hard while it's doing that it certainly doesn't just fix everything, but a couple times I thought that doing so I might be able to level out the surging and almost get proper behavior at mid throttle but I certainly can't get WOT even if squeezing the ball, it stalls. Can a fuel pump fail such that you squeeze to a "hard ball" even though you're not pushing fuel all the way to the carb? In other works, is it possible the fuel pump is bad and I can't overcome all problems just by squeezing?

What would you do next? Remember that squirting mixed fuel from a spray bottle into the carb throat makes this all go away, so it has to be a fuel issue right? Would you buy a fuel pump rebuild kit next if me? Or a new pump? How do these pumps actually generate pressure? Is the surging behavior telltale of anything? All I can think of doing next before giving up and taking to a mechanic is to replace/rebuild the fuel pump.
 
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LS1967gto

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Yes I have good spark compression is good carb was overhauled by a professional and still has not solved my problem. I still keep going back to the fact
that if I use the primer I can get it to overcome the dying out at high speed and when I quit it reverts back to stalling at full throttle but will idle fine. It has nothing
to do with overheating as again it will work fine if I use the primer. Help!!!
 
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Yes I have good spark compression is good carb was overhauled by a professional and still has not solved my problem. I still keep going back to the fact
that if I use the primer I can get it to overcome the dying out at high speed and when I quit it reverts back to stalling at full throttle but will idle fine. It has nothing
to do with overheating as again it will work fine if I use the primer. Help!!!
Did you ever figure out the issue? I have exact same problems and I even replaced my fuel pump
 
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