1994 evinrude 120 hp going into slow mode

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17rogue70

Petty Officer 3rd Class
Joined
Feb 21, 2010
Messages
93
i just aquired a 19' cc with a 1994 e 120 hp that the oil injection was terminated. while testing the engine after approx 3-5 min the engine goes into slow mode. pulled comp test ,all 127 across the board. all alarms were disconnected too. rescently replaced the whole water pump assembly and it is peeing good. checked it with an infrared temp gun ,never went over 127*. what else could it be,and is it easy to fix myself? max rpms are 5400 with a 14 1/2 x 21 ss prop. if i keep it between 4000 and 5000 rpm ,it doesnt go into slow mode. like i said , i just aquired this boat and engine . that is all that i know about this package. year and model # 1994 e120txarc. dont know if it has anything to do with it but we also changed out the tilt and trim motor.
 
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ezeke

Supreme Mariner
Joined
Sep 19, 2003
Messages
12,532
Re: 1994 evinrude 120 hp going into slow mode

S.L.O.W. is activated by the temperature switch closing, which grounds the tan wire leading from the cylinder heads to the powerpack. Check the wires, they may be shorting, or they may be too close to the spark plug wires.

The blocking diode in the harness should prevent other warning signals from activating S.L.O.W.
 
JPGBU1

JPGBU1

Seaman Apprentice
Joined
Aug 8, 2010
Messages
30
Re: 1994 evinrude 120 hp going into slow mode

Change out the thermostats. I had the same problem on a 115 and that was it. they were blocked a bit- the engine wasn't overheating but S.L.O.W. was kicking on... Also are you sure it is SLOW? not a fuel issue? I also know someone had the same problem and it was a bad valve in the primer bulb. I have also seen tempo tank brass valves cause issues. because the fuel couldn't get to it quickly enough...
 
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ezeke

Supreme Mariner
Joined
Sep 19, 2003
Messages
12,532
Re: 1994 evinrude 120 hp going into slow mode

Most earlier 115HP motors were crossflows and don't have S.L.O.W.

It's not activated by anything but a true overheat because it is triggered by the temperature switch, so unless the switch is faulty, you either have a short or you have a damaged powerpack.
 
1

17rogue70

Petty Officer 3rd Class
Joined
Feb 21, 2010
Messages
93
Re: 1994 evinrude 120 hp going into slow mode

new thermostats were installed ,there wasnt any in it when i aquired the boat. its not a fuel issue, i dont think . the primber bulb stays firm when this happens, i thought this too. i will check the wiring . thanks guys for the responces. even though the buzzers are un hooked do i need to keep the temperature wires hooked up ? also the engine wont go over 3100 rpms. if you try to exceed 3100 the engine studders or misses badly
 
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boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: 1994 evinrude 120 hp going into slow mode

After 1100 to 1200 rpm Quick Start is cancelled out. Sounds like you have something else wrong in your ignition system. As Ezeke said you could also have something in your tan wireing going to the temp sw grounding out or else a bad temp sw. Those blocking diodes in the wiring harness have also been known to go bad and that will also put you into SLOW. There's a procedure in the OEM service manual on how to check them out.
 
1

17rogue70

Petty Officer 3rd Class
Joined
Feb 21, 2010
Messages
93
Re: 1994 evinrude 120 hp going into slow mode

could that explain why there wasnt any thermostats in the motor? this one has me winding my butt and scratchin my watch
 
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