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'93 Johnson 25 hp not Getting Enuf Gas

G

gogittum

Member
Along with my '83 Johnson 15, I've been tussling with a fuel problem in my '93 Johnson J25TEETS and it's giving me fits.

The motor starts and runs fine....up to about 2,000 rpm....and won't go any higher. Idle along and it's fine. Hit the gas and it'll give a big boost and start to lift onto plane, then craps out - after maybe 1/2 to 1 second. Hold the throttle on and it'll gurgle and choke for a few seconds, then give another short burst.

It's a new-to-me motor, so 1st thing I did was go thru the carburetor with a full kit. No joy....same problem.

Rebuilt the fuel pump and checked the filter. No change, so put on a complete new fuel pump. No change.

I very carefully checked fuel pick up, hoses and squeeze bulb, thinking it might be sucking air. Then replaced all those. Nope.

Fuel line from connector at motor to fuel pump looked some ratty, so replaced it. No change.

After one trial at the local canal launch, I brought it home and pulled the plug out of the float bowl. There was hardly any gas in the float bowl, so pulled carb back off - remember, it's freshly rebuilt - and float level was correct and needle and seat functioning properly.

I left the plug out and squeezed the bulb. Gas immediately started flowing out of float bowl, so put the plug back in and went back down to the canal. This time when I hit the gas, I kept the squeeze bulb in my hand and squeezed it hard when I hit the gas and kept squeezing it hard - and the motor did the same thing - give a surge and die out.

I've tried several times to rent the fuel pressure gauge from O'Reilly's and someone had always beat me to it. Today I lucked out and got the gauge, so brought it home and hooked it up......with a lot of fussing and adapting.

1st, I connected it to the valve on the fuel enricher solenoid and didn't get a reading, so went to the fuel pump outlet. Nothing fit and it took some creative engineering to get a direct, solid connection but finally made it. No reading again. WTH ??

That's a new fuel pump, new hoses, new gaskets....?? Compression is 130 psi on both cylinders, but with it running, I squirted a bit of ether (diesel starting fluid) at the bottom of the motor and up under the flywheel, being very careful to keep it away from the carburetor.

There was no rpm change, so I'm "pretty sure" there's no air leaks around the crankshaft seals. With the motor running on the muff, I can shift it into gear and it'll rev for a bit, then start to stagger.

A couple of weeks ago a friend in Homosassa who's an outboard pro looked at it for me and spotted a crack in the fuel pick up in the float bowl and recommended a new carburetor. I found a used one at a parts yard and went thru it. No change from the original carburetor.

I dunno. I'm at my wit's end. The thing should go.....and it doesn't. Any ideas would be greatly appreciated. Thanks in advance.
 
So you have been replacing stuff without some simple trouble shooting ??----How much fuel pressure are you expecting to see on this motor ?
 
I do not believe fuel pressure will be that high.-----Does spark jump a gap of at least 3/8" on both leads , yes or no ?
 
In my 1st post I listed everything I've done in the way of troubleshooting. This isn't the 15 hp now - this is my 25 hp and it starts and runs fine - up to 2,000 rpm. Haven't checked the spark because it does start and run easily.

The scale on the fuel pressure gauge is pretty coarse - 0 to 20 psi is only about 3/4", but the needle doesn't even move with the motor running.

As I said above, it will idle down the canal fine, then when I hit the gas it surges up for less than a second and drops back. When I pulled the plug out of the float bowl, only a dribble came out....which leads me to think poor fuel flow. Double checked float level and it is correct.

For the life of me I don't know why. 1st I rebuilt the fuel pump, then went thru all the hoses and fuel pickup. Then replaced the fuel pump completely.

I did have a video camera running when I was on the canal, but it doesn't show the surging too clearly. I'll dig up the link and post it here in a bit.
 
Thanks. No idea of inlet needle and seat - they're what came in the kit. When I pulled the plug out of the float bowl and squeezed the bulb I immediately got a heavy flow of gas, so don't believe there's any restriction there, nor suction leaks below the bulb.

Float is triple checked for correct level and needle moves freely. I did replace the fuel hose and bulb and very carefully went over the pickup in the tank. No leaks.

I'm used to using Windows Movie Editor for videos and it's not available to me now. I did download a new one but it baffles me. The video isn't the best but does give a good idea of the problem.....if I can ever figure it out. Tomorrow's a new day.
 
Just went out to the boat with fresh eyes. I pulled the spark plugs on the 25 hp and cranked the motor. Good, hot spark on both cylinders - at least 3/8" to ground. As said before, the motor does run, but won't make any power.

8# fuel pressure is apparently more than I can expect, so I pulled the hose from fuel pump to carburetor and stuck it in a jar, then cranked the motor. It gave a steady fast pulsing that jetted out about 2" from the end of the hose.

The trailer for that boat, the 16 ft, has been at the welding shop for 4 weeks, waiting for a 2 hour repair. If you live in the Inverness, FL area, I can tell you which shop NOT to go to. It's s'posed to be ready today, yet again, so maybe I'll be able to put the boat in the canal this weekend and see how it does.

Does anyone know of an "easy" video editing program that even old farts can figure out ?? Since Microsoft made Windows Movie Editor unavailable, I'm stuck.
 
I went out to Al's in Inglis yesterday and picked up coils for the 15 hp. Don't want to cut wires on the 25 hp components - they're working and I want them to stay working.

OK...Picked up my - unfinished - trailer Friday and loaded the boat. Today, Sunday, I took it down to the canal for a test run.

Remember, this is a different carburetor now. I launched the boat in the canal and it started right up. A little ragged at 1st, but it did run, so I idled out to the end of the no wake zone and gave it gas.

Same exact thing as before - it surged half way up onto plane, smooth and solid - definitely running on 2 cylinders - then crapped out....and died. Got it started again and it surged and crapped out again. I fussed with the mixture needle in top of carb and got it smoothed out at about 2¼ turns/1200 rpm. No change.

I had brought an extra tank, squeeze bulb and hoses with me and switched tanks. No change.....still surges and dies.

I do hafta say I'm impressed with that little 10 amp motorcycle battery. It started that 25 Johnson about 20 times in a row this afternoon without a hiccup or slowdown. I'm sure my heartfelt cussing and screaming gave it encouragement.

It idles fine at about 1200 rpm, raggedly under 1000 rpm, shifts smoothly and accelerates smoothly....to around 2,000 rpm. Give it more and it sputters and craps out.

2 carburetors, 2 tanks/hoses, good hot spark.....I'm at a loss. The thing should go. Help.
 
I guess I've been blacklisted but don't understand why. In my 1st post I listed a whole row of things I've done and tried to get this thing going.

Sunday in the canal, I felt sick when it did the same thing with the new (used) carburetor. Migawd, I've said before that all I want is to get this fool thing running so's I can go fishing.

This morning I had a slightly different thought, so went out there and pulled the float bowl plug again and only got a dribble of gas. It was fully tilted when bringing it home and has been in running position since I got it home.

Then I cranked it with the plug still out and within a couple of seconds I got a good, solid stream of gas coming out of the drain. I think that's proof that fuel system up to that point is good.....but, as I say, there wasn't much gas in the float bowl when I started.

When I hold the carburetor upside down, the float is exactly level with the gasket surface. When I pull that float bowl drain plug, I don't get much gas out of it.

Seems logical to me that there isn't enuf gas in the float bowl to support high speed and, too, under acceleration the bow rises, which would change fuel level in float bowl as well.

This is consistent with 2 different carburetors. Would it be a good idea to raise the float level to allow more gas into the float bowl, or would that flood something else ??

C'mon, guys - I'm desperate and absolutely baffled. Could it be something in the ignition, maybe in the advance mechanism ??
 
Remove top plug wire and try and start this motor.------Then try and start with bottom wire off.-----Report exactly what you find.----Not what you think might be wrong !-----The high speed jet is way inside where you removed the drain plug on the float bowl.----About 5/8" long with a calibrated hole.-----Is that jet confirmed clean , yes or no ?
 
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Right....that jet could be partially plugged. Did you use the same float bowl on BOTH carbs? If the second carb came with the float bowl, then THAT jet could be partially plugged too.
To address a question about ignition, yes....it's possible that when timing is fully advanced, the carb is not opening up, but I'm quite sure you must have checked this. Second thought, if there is a bad wire coming from the trigger, it could be loosing continuity, or shorting to ground. You can test this with an ohm meter by removing wires leading to it, apply ohm meter to each wire....then operate throttle from low speed position, to wide open. Look for changes in continuity, especially where you would expect to begin the "bogging". A good visual inspection can help alot too. Also check flywheel key, could be why it's not idling well, either. Make sure carb is able to be fully closed at idle, with the timing itself actually directing idle speed. Have we confirmed the carb is opening at correct synchronization with timing? Has anything been modified or messed up by the previous owner?
 
Some simple testing will lead the owner to the ----" I see the light "--- moment.-----Needs to stop guessing as to what might be wrong.
 
racerone said:
Remove top plug wire and try and start this motor.------Then try and start with bottom wire off.-----Report exactly what you find.----Not what you think might be wrong !-----The high speed jet is way inside where you removed the drain plug on the float bowl.----About 5/8" long with a calibrated hole.-----Is that jet confirmed clean , yes or no ?
Click to expand...

OK, did as you said, and with each wire off in turn and motor started easily, but makes popping sound - rpms dropped from ~1100 to about ~>800. No problem.

Now....may have found the problem. I did use the old float bowl on the new carb because it has the mounting surface for the enricher, which the new one does not. In figuring out how to get the jet out of the one on the motor now, I experimented with the old setup and made a tool.

Awkward, but it worked - broken drill bit of the correct diameter cut to length & shape and it did remove the jet but was awkward with carb on motor, so epoxied a fitting onto the end of it for more precise control. The epoxy is curing now.

In my experimenting, I found that the jet in the original float bowl has a much smaller orifice than the one in the new float bowl, which I didn't use.

Who woulda thunk it ??

That was a gift from the previous owner.....maybe he used parts from a 9.9 or 15 hp ??

Seems to me, that smaller jet would starve the engine under high throttle openings and cause exactly my problem. I'll put the larger jet in. What think you ??

Not in a hurry to put it back together - that epoxy is curing and there are storms active on the Nature Coast right now, so can't put it in the water anyway.
 
So you have some Franken-parts going on which can lead to problems. The parts diagram shows a 51Dhigh speed orifice for a 1993 25HP. It's entirely possible that your low speed jet (#1) and the adjuster needler (#14) are correct for your engine which explains why it idles and runs perfectly at slow speed. If your HS jet is not matched properly that could explain your poor running above 2,000 RPM. If you were running a larger jet you may have been flooding the engine at higher throttle. To test that give the throttle the beans while running then pull the kill lanyard. Remove the plugs immediately and see if they are black and wet. If they are, you're running too rich. In the Jet ski world we call that a plug chop and it's very common setting up older 2-stroke skis when they've had mods and you're trying to dial in fuel delivery at higher RPM.

http://www.marineengine.com/parts/j...manufacturer=Evinrude&section=Carburetor+-+25
 
Is there a tag / part number on the carburetor you are using ?-----Carburetors off the 50 HP and 70 HP motors are very similar.
 
Is there a tag / part number on the carburetor you are using ?-----Carburetors off the 50 HP and 70 HP motors are very similar.----They appear to use the same carburetor kits from 25 to 70 HP for many years.------Who know , maybe there was a mix-up.
 
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