Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

[nvr-enuf]

My boat starts and idles great, but when I go to full throttle, it reachs full throttle for about 2 seconds then the engine all by it self goes into an idle mode, will not accelerate any more. Previous to this issue, I had the following work done:
- carbs cleaned
- fuel tank cleaned
- timing re set
- fuel lines replaced
- oil lines removed and either verified or replaced
- 2 electrical items replaced (maybe timing pick up and some other electrical box).

I refuse to take back to the local guy that replaced the two electrical boxes & labor charges. Don't ask and do simply state return it to the guy that worked on it. been there done that.

So, based on above, is there some kind of safety switch that could be telling the motor to go into a limp mode?

If yes, where is it located? Motor is a 3 cylinder 3 carb 2 stroke outboard 70 hp JOhnson tracker.

Thanks for all your help

 

[tashasdaddy]

Re: Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

time for trouble shooting check compression, spark on all 3 cylinders, could be carb high speed jets clogged. could be heat sensor sending it to safe mode. oil sensor. was you mech a certifed Johnson mech? could be fuel pump failing. clogged filter. block fuel tank vent, primer bulb collapsing.

 

[dale kennedy]

Re: Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

my 70hp johnson idles great on land but in water put it in gear and the engine dies to almost a stall and then I pop the choke and away it goes and runs great. does this all the time. done everything last person has done. My mechanic just scretches his head

 

[steelespike]

Re: Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

Does the motor actually go back to idle? 650 to 750 rpm?
What happens if you return the throttle to idle position and again advance it?

 

[oxbeast1210]

Re: Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

im having similar issues please post back if you figure it out
thanks

 

[Joe Reeves]

Re: Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

Model TJ70TLESF is a 1990 70hp Johnson.

If that engine has safe mode as Tash suggests which I assume is the same as the S.L.O.W. mode feature (Does it Tash?), a engine that overheats very quickly would have the rpms dropped suddenly... how far on a 3 cyl model I have no idea. A faulty overheat sensor in the cylinder head would have the same effect.

If engaging the S.L.O.W. feature, turning the key OFF, wait a second or two, then restarting the engine should allow hitting full throttle again and re-entering the problem cycle.

However, to prove or disprove this flaw, simply disconnect the wires leading from that overheat sensor, then test run the engine. If this cures the problem, DO NOT continue to run the engine or risk overheating the engine to a point of destroying the powerhead.

To test a possible fuel pump problem, simply pump the fuel primer bulb constantly, acting as a manual fuel pump. If this cures the problem, rebuild or replace the fuel pump.

If the fuel pump primer bulb has a tendency to be drawn flat, suspect a fuel restriction, the most common one being a sticking anti siphon valve... as follows.

(Fuel Anti Siphon Valve)
(J. Reeves)

Many of the later OMC V/6 engines incorporate a fuel restriction warning via a vacuum device attached to the powerhead. If the engine overheats, or if you have a fuel restriction, the warning is the same.... a steady constant beep.

NOTE... Only the V/6 & V/8 engines have the above "Fuel Restriction Warning". The warning horn will not sound on the other models.

The fact that a engine is not overheating, but the warning horn sounds off with a constant steady beep, and that the rpms drop drastically would indicate that the engine is starving for fuel due to a fuel restriction. Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve which is notorious for sticking in a semi closed position. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. If this valve exists, remove it, knock out those inner components which will convert it to a straight through fitting, then re-install it. Hopefully that cures the problem.

The above procedure will cure a restriction problem with the anti siphon valve as stated. BUT, it may also allow fuel to drain backwards to the fuel tank when the engine is not running (siphoning backwards) due to the fact that the carburetors/fuel pump etc are higher than the fuel tank. This condition is not an absolute as the valves in the fuel primer bulb usually prevent this backwards siphoning problem. However.... if this does take place, the cure would be to install a new anti siphon valve.

Let us know what you find.

 

[dale kennedy]

Re: Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

Does the motor actually go back to idle? 650 to 750 rpm?
What happens if you return the throttle to idle position and again advance it?

same thing

 

[dale kennedy]

Re: Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

does not go back to idle simply will stall

 

[ezeke]

Re: Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

If the powerpack has entered S.L.O.W. mode, you will have to turn it off and wait for it to cool before it will return to normal.

S.L.O.W is only activated by overheating the engine. A blocking diode in the engine harness prevents other warning signals from activating it.

 

[dale kennedy]

Re: Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

If the powerpack has entered S.L.O.W. mode, you will have to turn it off and wait for it to cool before it will return to normal.

S.L.O.W is only activated by overheating the engine. A blocking diode in the engine harness prevents other warning signals from activating it.

why then does the motor run fine after I pop the choke if it is over heated. this prosses starts after every time I start the engine?

 

[Joe Reeves]

Re: Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

This thread started out with member "nvr-enuf" who joined in 2008, now has 36 posts and a problem with a 1989 70hp Johnson.

It quickly got switched over to member "dale kennedy" who joined in 2010, now has 4 posts, and a problem with a ? 70hp?

What happened to "nvr-enuf"? Am I missing, overlooking something here?

 

[mables]

Re: Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

Joe it seems dale ressurected a dead thread. nvr-enuf's and tasha's posts were from 09

 

[ezeke]

Re: Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

why then does the motor run fine after I pop the choke if it is over heated. this prosses starts after every time I start the engine?

Obviously, you are not in S.L.O.W. mode.

If performance inproves when you use the primer solenoid on a warm engine, it almost always indicates that you have a gasoline supply shortage (A/K/A running lean).

 

[Joe Reeves]

Re: Johnson Tracker 70hp TJ70TLESF 1989? - goes into limp mode

Mables.... Aha, a 2009 thread ressurected! I missed that completely.