Evinrude 120 rev-limiter???

[scrapinchevy]

I have a 1988 evinrude 120 (VRO disconnected, mix my own, 50:1) that has developed a problem. When you run it on plane (around 3500-4000 rpm) for 5 or so minutes, it starts to miss like there is a rev limiter kicking in. At first I thought it had fouled the plugs, but it did it again with new ones. I have checked all the fuel lines and filters (changed, even the one in the tank) and have pulled the carbs apart to see if anything was lodded in the jets or needles. Evertyting looks to be fine. I know my way around an engine really well , but this is stumping me beyond belife. Oh, on the last outing, I disconnected the temp. sender wires from both heads, one orange on the right side and one orange and a white from the left side. After I had done that the motor ran without a hitch. I am thinking that one of the senders is bad, but it could also be the power pack. Any thoughts, I don't want to run the motor too long without the temp sensors off. please help....

 

[VistaMan]

Re: Evinrude 120 rev-limiter???

Don't the temp sensors just short to ground to sound the alarm horn? They do on my '86 but then maybe they are tied to the ignition to reduce RPM when overheating like on my Nissan. I would check with the manual and see if they are meant to reduce revs on over heat.

 

[Cricket Too]

Re: Evinrude 120 rev-limiter???

scrapinchevy.....Don't think it is your rev limiter if it's between 3500-4000 rpm, that's a pretty low rpm for an outboard, the rev limiter probably kicks in around 6000 or a little higher. What made you disconnect the temp. sensors, did the horn start to sound or did you just do it for the hell of it?

 

[rodbolt]

Re: Evinrude 120 rev-limiter???

hello<br /> I will admit orange wires are stumping me. maybe to much chevy . I think the wires are Tan. and the port side should be tan and possibly a tan and white.<br /> in 1988 or 89 the port head contained the sender for quick start. that sender has 1 tan wire and one white/blk tracer wire. your motor is equipped with S.L.O.W. it is a speed limiting overheat. it works when the maintenace on the alarm horn and circuits has not been properly done.you really need to test the sensors and the alarm circuits and horn for possible malfunctions. sounds like you are suffering an overheat the next symptom you may post is about the automatic shut off. only there is no auto shut off. it will auto shut down when the pistons expand enough to stick to the cyl walls. check with iboats and get a service manual pronto.<br /> good luck and keep posting

 

[scrapinchevy]

Re: Evinrude 120 rev-limiter???

Thanks to all who have replyed. Yes, it is a tan/white whire and a white with a black tracer, and when i ground the tan wires the alarm does go off. as far as an overheat problem, it flows good water and it is not hot or doesn't steam. I an thinking that either the sensors are being flaky or the powerpack is acting strange, thats what i have narrowed it down to....

 

[Solittle]

Re: Evinrude 120 rev-limiter???

Listen to rodbolt "------and get a service manual pronto."

 

[quinnf]

Re: Evinrude 120 rev-limiter???

Y'know, that _really does_ sound like fuel starvation, though you said you've already checked that out.<br /><br />Friend of mine spent thousands of dollars getting his 120 to run. More, in the long run, than he would have, had he just bought another engine. Nothing worked until his hired wrench pulled the tank access panel and peered inside. Seems a leaf got in there and after running a while somehow found the intake screen. As soon as he would idle down, decreased suction released the leaf which would then float away. You might do a visual for debris in the bottom of the tank.

 

[Walker]

Re: Evinrude 120 rev-limiter???

"Oh, on the last outing, I disconnected the temp. sender wires from both heads, one orange on the right side and one orange and a white from the left side. After I had done that the motor ran without a hitch."<br />That leads me to believe it a problem with the SLOW system. Start there.