Evinrude 40hp about 1996, SLO feature

I have a 40 hp Evinrude that has the S.L.O. feature. It kicked it yesterday as I was running. First the "check engine" light came on, along with an alarm. I slowed to an idle and checked the tell tale, a good stream of water was coming out. The engine idled fine. I put the engine in reverse to clear any debris from the intakes. After a few seconds the light and buzzer stopped. However, when I tried to come up on plane again, the engine would speed up and then immediately drop back to a fast idle, the repeat this sequence as long as the throttle was forward. I only had about a mile to go to the dock and "fast idled" the way in. After about an hour I tried the engine again and it worked fine,.

My questions: is there something other than temperature that can cause the SLO feature to kick in? And, if I had shut the engine off, would that have "reset" the SLO switch? This assumes the problem, if overheating had gone away.

The engine is self oiling (not mixed gas) and the oil tank is almost full. Again, everything seemed to work fine after the engine cooled and was restarted.

Many thanks.... Dan

Re: Evinrude 40hp about 1996, SLO feature

Dan said:

I slowed to an idle and checked the tell tale, a good stream of water was coming out. The engine idled fine. I put the engine in reverse to clear any debris from the intakes. After a few seconds the light and buzzer stopped. However, when I tried to come up on plane again, the engine would speed up and then immediately drop back to a fast idle, the repeat this sequence as long as the throttle was forward. I only had about a mile to go to the dock and "fast idled" the way in. After about an hour I tried the engine again and it worked fine,.

My questions: is there something other than temperature that can cause the SLO feature to kick in? And, if I had shut the engine off, would that have "reset" the SLO switch? This assumes the problem, if overheating had gone away.

The engine is self oiling (not mixed gas) and the oil tank is almost full. Again, everything seemed to work fine after the engine cooled and was restarted.

Many thanks.... Dan

Click to expand...

The SLOW system will remain on until the engine cools and you turn the key off to reset it. It can be activated by overheating, which I suspect is what happened to you, by a malfunctioning temp sensor, or by a malfunction in your power pack.

Re: Evinrude 40hp about 1996, SLO feature

A sticky thermostat will cause an overheat condition which will trip the SLOW function. If you run in salt or brackish water the stat may be corroded or gunked up and should be replaced. If the alarm was a steady beep -- that signals an overheat. Just because the tell tale shows a good stream does not mean the engine is being cooled. If you can touch the head for 10 seconds or so, it's probably not overheating and the problem may be a touchy temp sensor. If the engine feels hot when the alarm goes off, it is overheated.

Re: Evinrude 40hp about 1996, SLO feature

I found the problem!

I had pulled the oil tank out (along with the battery) to install a float switch for the sump pump. When I reinstalled everything, I crimped the rubber hose that carries oil to the engine. At high speeds, the engine was not getting enough oil. Once I moved the oil carrying hose around so it was straight, the problem has not reoccured. All seems to be OK now.

I have concerns about any damage I might have done to the engine, but it seems to be OK. The SLO seems to have done its job.

Also, the reply about the function of the SLO feature was correct. I found that once the engine cooled and I had turned the engine off, it reset the SLO switch and the engine could be run at high speeds again.

Thanks for the help.

Dan

Re: Evinrude 40hp about 1996, SLO feature

you found what is was going to suggest. probably did little on no damage, as the slo worked.

Re: Evinrude 40hp about 1996, SLO feature

I'm pretty sure on that year system check you only get one kind of warning. It's always a steady, loud alarm and then a light on the gauge will show the problem system. You will get the same alarm for low oil, no oil, fuel restriction and overheat, but a different light for each on the gauge.