4 HP loses power after 10 minutes - good water stream

[djmeaney]

My 2000, 4 HP Johnson - J4RLSS loses power after 5 - 10 of pushing my boat. The engine seems gas starved and will only run at slow speed -- otherwise it stalls. Makes no difference if I pump the primer bulb. I rebuilt the carb last fall and it ran like a top. It was winterized by running out all the fuel and fogging the engine and storing in the basement. When I went to use the motor for the first time last this year I experienced the power lose issue.

When I fist ran the engine this year this was no stream from the "pee-hole", but a little poking and prodding with a piece of wire took care of that. Now there is a good, strong stream. Alos notice that the water temp from the pee-hole is very warm, not hot enough to burn -- may be hot tune warm.

I checked the service manual and this engine does not appear to have a thermostat.

Bought the motor last year, not sure what has been done on it other than the carb rebuild I did.

Any help/suggestions would be appreciated.

Thanks,

Dan

 

[Rick.]

Re: 4 HP loses power after 10 minutes - good water stream

My gut feeling is your carb. high speed circuit is dirty and needs to be cleaned. I know you already did it but a little flake of fuel line can make it dirty again in a heart beat. Also check for spark when the power/rpms drop. You could be loosing spark from one coil. Best of luck. Rick.

 

[jonesg]

Re: 4 HP loses power after 10 minutes - good water stream

..and open the tank vent.

 

[djmeaney]

Re: 4 HP loses power after 10 minutes - good water stream

Recleaned Carb -- no difference!

This motor does have both an external fuel connector (which is what I use) and an integral fuel tank. I switched back and forth between them no apparent difference in performance. Made sure vent was open on internal and external tanks (actually unscrewed cap on external tank to make sure there wasn't a vacuum/vent issue).

The engine still loses power, but it will come back intermittently and then bog again. When I pull the choke out it dies quickly. So far, I have always been able to get it to start and run at low speed.

The water from the pee hole was almost too hot to touch at times -- and then just very warm at others (don't believe this motor has a thermostat).

Will keep troubleshooting...

 

[Rick.]

Re: 4 HP loses power after 10 minutes - good water stream

What about the spark check? Did you do it? As far as the hot water goes you may well need a new impeller. With no stat it should never get very hot. Mine is always just warm. Rick.

 

[djmeaney]

Re: 4 HP loses power after 10 minutes - good water stream

Thanks for the suggestions.

I checked spark with old timing light and it looked fine --- there a few skips, but I think that was because the engine rpms were faster the the light could handle (about half-throttle).

It may be time to call in the professionals....

 

[jonesg]

Re: 4 HP loses power after 10 minutes - good water stream

OK, do a compression test. if ok...

run it til it starts losing power, then use an adjustable spark tester, set gap on the tester to 3/8th inch and see if it will jump the gap.
Suspect the coil failing when warmed up.

If you don't find a problem with spark, timing light will not show spark quality btw,

rebuild carb with carb kit.

Compression guage and adjustable spark testers are cheap at auto stores.
Don't buy the neon spark flasher, you need the air gap type, adjustable.
Cost about $10.

 

[djmeaney]

Re: 4 HP loses power after 10 minutes - good water stream

I'll give it another go over the weekend.

May also take a closer look at exhaust housing and cylinder heat for signs of restricted cooling passages. Tell tale was blocked when I first started this season (until I poked a wire into it) may there is some crud causing problems.

 

[djmeaney]

Still having problems throttling up when warm

Still having problems throttling up when warm

Can't seem to get this problem fixed! (2000 Johnson 4 HP J4RLSSM)

Motor will run okay (runs a little rough -- rpm bounces around a little bit) at slow speed and will throttle up with no problems when first started. Once the engine gets warm it will bog down when I open the throttle (under load and not under load) unless I quickly pull out the choke and quickly push it back in. If I do that the motor catches -- and the rpms go up.

• I have rebuilt the carb (using a kit) following the instructions in the secret file.
• replaced the fuel lines to and from tank and fuel pump
• synchronized the carb
• replaced plugs
• replaced water pump
• check spark @ 3/8" gap appeared to be good and strong
• used new fuel

None of this had made a significant difference -- very frustrating. Only thing I haven't done is check compression.

Any other suggestions?

 

[Daviet]

Re: 4 HP loses power after 10 minutes - good water stream

The statement "quickly pull out the choke and quickly push it back in" makes me think you have a carb problem.
When you cleaned the carb did you remove the high speed orifice and nozzel and make sure they were clean? Did you remove the core plug on top of the carb and make sure all the passages are clean? In front of the core plug there should be a small lead plug in the top of the carb, is it there?

 

[djmeaney]

Re: 4 HP loses power after 10 minutes - good water stream

Yes to all of the above.

I did remove the high speed orifice and nozzle - they soaked in carb cleaner (along with carb body) overnight -- although they looked real clean going in.

Also removed the core plug -- area under that was also real clean -- replaced with new plug.

Used a couple of strands of wire to make sure passages were open.

all lead shot plugs are where they are supposed to be (didn't remove these).

 

[jonesg]

Re: 4 HP loses power after 10 minutes - good water stream

try spraying fuel into the carb throat when it bogs down.
sounds like fuel restriction in low speed jet.

 

[djmeaney]

Re: 4 HP loses power after 10 minutes - good water stream

I'll give that a try.

I am tempted just to buy a new carb for $275......

 

[zebra7]

Re: 4 HP loses power after 10 minutes - good water stream

I have the exact same problem with my 8 hp Johnson and have tried everything, well obviously there is one thing I haven't tried
Have you had success fixing your problem?
Mine runs for 15 min then stalls out, but I can sometimes limp along playing the choke for a while. Fuel still entering the engine, spark still being produced but obviously not enough of one of them.
I would think that because the choke can sometimes help things along, that it has to be in the carb, but it is as clean as a whisle, and the consistant timing of the problem tends to lean more towards ignition.
What ignition problem could be affected by the choke?
I would appreciate any input.

 

[Wingedwheel]

Re: 4 HP loses power after 10 minutes - good water stream

I would still wonder about the coil.

 

[djmeaney]

Re: 4 HP loses power after 10 minutes - good water stream

I have the exact same problem with my 8 hp Johnson and have tried everything, well obviously there is one thing I haven't tried
Have you had success fixing your problem?
Mine runs for 15 min then stalls out, but I can sometimes limp along playing the choke for a while. Fuel still entering the engine, spark still being produced but obviously not enough of one of them.
I would think that because the choke can sometimes help things along, that it has to be in the carb, but it is as clean as a whisle, and the consistant timing of the problem tends to lean more towards ignition.
What ignition problem could be affected by the choke?
I would appreciate any input.

I think my problem has been solved -- although I never got a chance to truly test it on my boat -- I did get it to run its best barrel test yet at the end of the year. It did turn out to be something in the carb. I must have cleansed that 4 times -- soaking overnight in carb cleaning fluid. I'll let you know if a few weeks if that was really the problem.

Dan