1988 Johnson 225 goes to slow mode

[tgleeson]

Every trip the the motoer goes to SLOW mode.<br />I run boat at 3800 RPM, boat runs fine, will run over 5000 RPM, but every trip the motor goes to slow mode at least one time. When this happens the RPM drops to about 2000-2500. I pull the control to neutral and wait till idle smooths out (20-60 seconds)then we are good to go. Boat will run 7-10 miles with no problems. Any ideas would welcome.<br />I checked fuel lines, tank, filters.<br />No horn when this happens.

 

[Daniel Beckman]

Re: 1988 Johnson 225 goes to slow mode

Well, dont know if it could be the same prob that i got.<br />But my engine would not run over 4800 rpm.<br />After checking everything i finaly found out that it was the shift switch that make this happen.<br />So i pull the shift switch out of its holder and after that i got no prob.<br />You can search on shift switch here on ibots to read more about my prob.

 

[ob]

Re: 1988 Johnson 225 goes to slow mode

With the key in the "on" position,ground the tan temp sensor wires to block one at a time and the constant alarm should sound.If not ,you're horn may be defective and engine may very well be overheating and going into s.l.o.w. mode.Not sure what year they introduced the s.l.o.w. system ,but if equipped ,yours must be one of the first.

 

[tgleeson]

Re: 1988 Johnson 225 goes to slow mode

I already checked the temp senors, the horn blows when they are grounded. Is the shift switch in the slow circuit?

 

[ob]

Re: 1988 Johnson 225 goes to slow mode

No.The shift interupter just mometarily kills power to one bank when shifting from in gear to neutral.The s.l.ow. feature is within the powerpack which gets its signal from the temp sensor.

 

[seahorse5]

Re: 1988 Johnson 225 goes to slow mode

If you are using a non-suppressor spark plug, such as an NGK or a Champion L-77Jc4, the radio frequency interference (RFI) can sometimes put the engine into SLOW. Be sure to use only the QL77JC4 plugs. An open plug wire, arcing coils, rusted connector, etc. can also contribute to RFI.<br /><br />Another little known problem is a shorted isolation diode in the wiring harness near the red connector. A service bulletin locates the diode and gives the part number for different model motors.

 

[Daniel Beckman]

Re: 1988 Johnson 225 goes to slow mode

Well on my engine the shiftswitch was just a little pushed at high rpm and that little was enough to get the engine kill, like OB say one bank.<br />After it happens i have to get to neutral to "reset" again.