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Johnson 40 HP Outboard

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BrentMcCabe

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Hello. New to this forum and new to boating. Thanks for giving me a place I could come to ask a question. I have a boat with a 1988 Johnson 40 HP outboard motor on it. I have not worked on an outboard motor before but, for the past weekend, I am up to my elbows in it. It has the electronic choke, pushing in the key energizes the choke. This motor starts every time, it runs for 5 seconds, then dies. I have learned that if I keep pushing in the key to energize the choke, it will stay running. Then, every time it starts to die, I push in the key and it brings it back to like. I can never put it in idle and engage the propeller though. As soon as I put down the lever to be able to shift, the motor dies. So, as the motor runs, it starts to wind down like it's going to die, I push in the key and the motor comes back. I let it set another 5 or so seconds, it wants to die, so I push the key in again for the choke, it comes back to life. I did this for 10 minutes yesterday, thinking that if it would warm up, it would stop doing this........but it never stopped doing it. I put a new fuel filter on, bought a new gas tank. I took the fuel hose off after the fuel pump and I wasn't seeing much gas spurting out however, I have never worked on one of these before so I don't know what "normal" gas flow looks like. I don't have a pressure gauge that I could put on it to watch that. If anyone here has any suggestions, I would love to hear them. Thank you.
 
Is this engine new to you or have you owned it for some time and this problem just popped up?

That engine has a "Fuel Primer Solenoid" instead of a "Electric Choke" (See description below)

Your post indicates either a fuel/air leak somewhere between the fuel pump and the fuel supply or a failing fuel pump (VRO).

A fuel leak should be obvious. To check for a failing fuel pump, simply have someone constantly pump the fuel primer bulb (acting as a manual pump)... if that cures the problem, either rebuild the pump with a kit or replace it. If there is no change at all, the carburetors may be clogged, fouled, gummed... in which case remove, clean, and rebuild them as needed.

********************
(Fuel Primer Solenoid Function)
(J. Reeves)

The RED lever...... The normal operating/running position is to have that red lever positioned over top of the solenoid and aimed at the other end of the solenoid, gently turned to its stop. This is the normal/automatic mode position. Pushing the key in opens the valve within the solenoid allowing fuel to pa$$ thru it in order to prime and start the engine. Looking upon this solenoid as a electric choke results in a better understanding of it.

Having that red lever turned in the opposite direction, facing away from the solenoid, allows fuel to flow thru it to the crankcase area. One would only turn the red lever to this position in a case where the battery might go dead and the engine had to be started via the rope pull method. Look upon putting the red lever in this position as moving a choke lever on a choke equipped engine to the full closed position. Either one would supply fuel to the crankcase/engine for starting purposes BUT if left in that position while running would flood the engine.

The later model primer solenoids are equipped with a schrader valve, used for attaching a pressurized can of fogging oil etc, available at your local dealership with complete instructions.

Pumping the fuel primer bulb up hard fills the carburetor float chambers of course, but that process also applies fuel pressure to the primer solenoid.


The two small hoses leading from the primer solenoid branch off via tees to each fuel manifold section that would feed fuel to the individual cylinders.


Pushing the key in activates the primer solenoid to allow fuel to flow thru it to the intake manifold pa$$ageways. Cranking the engine over causes the fuel pump to engage which in turn sends fuel pulses to the primer solenoid via the 3/8" fuel hose.


Some engines incorporates the "Fast Start" feature which automatically advances the spark electronically so no advance of the throttle is required for starting.
Engines that do not have the "Fast Start" feature will be required to have the throttle advanced slightly.


Starting procedure: pump fuel bulb up hard, crank engine and push the key in at the same time. When the engine fires/starts, release the key so that it falls back to the run position.


Bottom line..... Look upon the primer solenoid as an electric choke.
**********************

Let us know what you find.
 
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When you push in the key with engine running the solenoid puts fuel into the motor.----This fuel bypasses the carburetors.----This would indicate fuel pressure from the pump.------It clearly points to problems in the carburetors.-------They are not hard to clean and usually no parts needed.
 
Thank you joereeves for the reply.

This engine is new to me. The model number is J40TlCCS. Serial #G7724144

I only assumed fuel pump because filter was changed and I expected I should seegas shoot skyward when I disconnected the line and turned the motor over. I didhave muffs on with water flowing. I watched several youtube videos, trying toresolve this. I tried to squeeze the bulb yesterday, to keep it running and ithad no affect. I could see it fill the fuel filter so I know gas is making itat least that far, consistently. I then took the hose that goes to this plasticmanifold looking thing that has 4 hoses branching off of it. I turned the motorover a few times and gas pumped a couple of light spurts then nothing. It willrun 5 seconds, then die. As I hear the motor about to die I push in the key andthe motor stays running. If I don't do this though, the motor does die. I alsobought a new gas tank. The "red lever" on the motor must be turned all the way to the 3'O-clock position or the motor wont start at all. Thank you

 
The 3 O'clock mention of the RED lever of the primer solenoid means very little to me as I don't recall exactly how that solenoid is situated on that engine... however, taking a guess... I assume that you mean that it is aimed straight out to the starboard side (same side as the gearshift). Reread my reply about its function above... it's either to be aimed straight back at the other end of the solenoid (automatic, works with the key pushed in)... OR... aimed straight away from the solenoid (manual, fuel flows through it constantly).

To test.... trace one of the small hoses leading away from the solenoid to whatever its attached to (carburetor or intake manifold) and disconnect it. Have that RED lever in the automatic position, pump the fuel primer bulb up hard, view the end of that loose hose and with the key in the ON position (not running), push the key in. You should hear the solenoid click and fuel should shoot out of the end of that hose. (Your explanation indicates it is functioning properly).

That plastic thing with a bunch of hoses (4) connected to it is indeed called a "manifold". One hose supplies fuel to it, one hose leads to the primer solenoid, two hoses lead to the carburetors.

Look at the sides of the carburetors... at the bottom side of the float chambers. Removing one of those drain screw plugs and looking at the backside of it (coloration) will give you a good idea of what the inside of the carburetor looks like. As "racerone" above suggests, I would suspect they are fouled and need cleaning/rebuilding. The fact that you can pump the fuel primer bulb (acting as a manual fuel pump) and this creates no difference indicates a carburetor problem.
 
Thank you everyone for your input. I am reading over all your information and advice. I wasnt able to do anything today but order a new fuel pump. Even if that isnt the problem, it cant hurt, right. I spoke with previous owner today and he said he had to push the key in a bunch of times also, to keep it running. After a while it remained running. I did it for almost 10 minutes and it didnt stay running. Do you think I would be able to take carburetors apart and clean, that I will need rebuild kits first? Thank you
 
Your problem is not the fuel pump... you proved that by pumping the fuel primer bulb (acting as a manual fuel pump) in an attempt to keep the engine running (bypassing the engine's fuel pump).

Yes, you would be well advised to have carburetor kits on hand as therein lays your problem.
 
Yes Sir, I get that. When I took my carburetors off last night and laid them on my work bench, gas leaked out. I would expect that. What I wasnt expecting was both bowls were bone dry! I wiped my finger in both, expecting to feel something wet.......nothing, both were completely dry.
 
BrentMcCabe said:
Yes Sir, I get that. When I took my carburetors off last night and laid them on my work bench, gas leaked out. I would expect that. What I wasnt expecting was both bowls were bone dry! I wiped my finger in both, expecting to feel something wet.......nothing, both were completely dry.
Click to expand...

We think you're on the right track... new kits will include the float needle valve assemblies. Notice the drain screw plugs on the front lower portion of the float chambers, way in back of them lay the brass high speed jets in a horizontal position in the center bottom portion of the float chamber... one to a carburetor (2 total), kept in place via 1/4x20 threads.

Make sure that all of those jets are absolutely clean... carefully clean them with a piece of single strand steel wire as solvent just doesn't do that job properly.
 
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Good news! The motor runs now, without pushing in the key. Thank you to everyone here. I can keep it running until I push that throttle lever down. It wont allow me to put the prop in gear until this lever is all the way down. But hey, at least its running. ��
 
Did you turn the slow needles all the way in to lightly seated and then turn them out 1 1/2 turns each? Thats called the warm up lever you should be able to push it back down shortly after starting it. You can tell bv the tone when the motor is warm enough to drop the idle speed maybe a minute or two.
 
kimcrwbr1 said:
Did you turn the slow needles all the way in to lightly seated and then turn them out 1 1/2 turns each? Thats called the warm up lever you should be able to push it back down shortly after starting it. You can tell bv the tone when the motor is warm enough to drop the idle speed maybe a minute or two.
Click to expand...
Oh no, I didnt tighten anything and then back it off. I am not sure what a slow needle is.
 
Is this the "slow needle" you speak of? I did take this out before I soaked the carb overnight in the cleaner. I tightened this screw down tight, but didnt back it off. It sounds like I will be taking the carburetors off again. :)
 
BrentMcCabe said:
Is this the "slow needle" you speak of?
Click to expand...

The 1988 40hp model did not have any adjustable needle valves (high or idle). It incorporates fixed jets.

I assume that you're saying that the engine dies out when you apply throttle...... There is a fixed brass high speed jet located horizontally in the bottom center portion of the float chamber, way in back of that drain screw plug. If it is slightly clogged, gummed, fouled, the result will be having the engine fall on its face (die out).

If this is the case, clean that jet carefully with a piece of single strand steel wire as solvent just doesn't do that job properly.
 
joereeves said:
The 1988 40hp model did not have any adjustable needle valves (high or idle).

I assume that you're saying that the engine dies out when you apply throttle.......
Click to expand...

Thank you for telling me it doesnt have those needles, because I couldnt find them on my carburetors.
If I leave it at a relatively high idle, it doesn stop. When I push that bar down on the remote control, to idle so I can engage the propelar, thats when it dies.
 
BrentMcCabe said:
If I leave it at a relatively high idle, it doesn stop. When I push that bar down on the remote control, to idle so I can engage the propelar, thats when it dies.
Click to expand...

On a flushette, depending on the engine's shaft length, the idle rpm should be...........

20" shaft = 1000 rpm
25" shaft = 1200 rpm

When the engine's actually in the water, the exhaust back pressure will cause the idle rpm to drop to normal.

With the above in effect, if the engine still dies out, do a re-check of the compression, ignition/spark and get back to us.

Compression should be approximately 100 psi and fairly even on all cylinders.

Spark (with all s/plugs removed) should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP!

Spark plugs should be Champion QL77JC4 plugs gaped at either .040 (strong spark) or .030 (long life).

Let us know what you find.
 
joereeves said:
On a flushette, depending on the engine's shaft length, the idle rpm should be...........

20" shaft = 1000 rpm
25" shaft = 1200 rpm

When the engine's actually in the water, the exhaust back pressure will cause the idle rpm to drop to normal.

With the above in effect, if the engine still dies out, do a re-check of the compression, ignition/spark and get back to us.

Compression should be approximately 100 psi and fairly even on all cylinders.

Spark (with all s/plugs removed) should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP!

Spark plugs should be Champion QL77JC4 plugs gaped at either .040 (strong spark) or .030 (long life).

Let us know what you find.
Click to expand...

I dont know how to check compression. Do I take the carb out again? Also, I dont have a tachometer on the boat. Inside the motor head area, I think its called. I have an electrical connector with 3 pins, is this to connect a tach? I also have a black wire that has a one wire connector on it. Could that be the tech!Thank you
 
If you can get at the high speed jets, there would be no need to remove the carburetors. The jets have a 1/4x20 thread and are screwed into place. You can make a tool to remove them.... a screwdriver with a shank that just clears the threads of the drain screw plug in the float chamber. Cut the tip off the screwdriver and file the end to be identical to the tool you see at the end of this reply.

The 3 wire connector, if a tachometer connector plug, would have the wire colors as:

Black == Ground
Purple = Voltage supply (12v)
Tan. == Tachometer sensor

Any dealership, this site no doubt, marine type stores, would have the proper plug in tachometer. A dial on the back of the tachometer needs to be set.... set it to #6 if you purchase or borrow one.

Taking compression is a simply task, as follows:

1 - Purchase a hand held compression tester that had a rubber cone shaped end that can be inserted in a s/plug hole. They're reasonably priced and available anyplace that automotive parts are sold.
2 - Remove all spark plugs.
3 - Make sure the KEY is turned to OFF.
4 - Insert the tester into the plug hole of the cylinder to be tested.
5 - Using a small jumper wire, jump from the large battery cable terminal of the starter solenoid to the 3/8" nut terminal of the solenoid that engages the solenoid (not the 3/8" nut terminal wire that leads to ground.)

This results in having the engine crank over (rotate) so that the piston will register the compression on that hand held gauge. The reading is considered as PSI (Pounds per-Square Inch).

317002a_CARB-JET_REM-INST.jpg
 

I have responded a couple of times last week but don't see them. I don't know if this carries over to another page and I am just not seeing it. I put a compression tester on it however, I had to turn the motor over using the key. When I tried the wire it got to hot to hold. The gauge read 120 for the top cylinder and 119 for the bottom. I had to pull the carbs off to remove the main jets. Both were very solid in place and I wrecked them while getting them out and am in the process of buying new ones. Before I did that I changed the spark plugs and ran a piece of wire through the main jet, which lies in front of the float bowl drain screw. Believe it or not, the motor ran worse after I did that. So I took the carbs back off again to get at those main jets, made a screw driver as you recommended, and it took a lot of force to loosen them, that's how I damaged them. I didn't blow off your advice, I don't know why my previous comments are not here.
 
The jumper wire should not have got hot at all if you connected it properly..... NOT from large bat terminal to large starter terminal.... connect from large bat terminal to small 3/8" nut terminal that causes solenoid to engage.
 
joereeves said:
The jumper wire should not have got hot at all if you connected it properly..... NOT from large bat terminal to large starter terminal.... connect from large bat terminal to small 3/8" nut terminal that causes solenoid to engage.
Click to expand...

My bad, and I know you gave specific instructions. The only nut I saw went to the metal body of the starter, which appeared to be ground.
 
I have taken the carbs apart again and cleaning the jets really good with isopropyl alcohol, like the repair book says. I noticed something that may or may not be of. Importance. The drain screw on one of the carbs has black on the end, and it cant be cleaned off with my thumb nail. The same screw for the other carb looks like new, shiny silver in color. I purchased two new high speed jets as the old ones for both carbs were frozen into position and almost impossible to get out.
 
The coloration indicates that the carburetor was fouled bad at one time... or possibly presently.

The jet removal requires having a screwdriver like tool with its shaft being a size that just clears those 1/4x20 threads and the tip machined as follows:
317002a_CARB-JET_REM-INST.jpg
 
Yes Sir, I followed your directions and custom made a screw driver. There was no other way for me to remove them, as one was really stuck and required a lot of force to get out. The other one was in pretty good as well but required a little less force to get it out.
 
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