theviolentvicar
Cadet
- Joined
- Jun 2, 2008
- Messages
- 23
So I?ve been having persistent overheat warnings from my 1990 70 hp Johnson with VRO. The behaviour is that, at or above approximately 4300 rpm, an apparent overheat warning was being generated after about 3 minutes. In trying to trace the problem, I did all of the following over the past year or so: replaced water pump and housing, replaced thermostat (twice), replaced temp sensor (twice ? once because the store sold me the one without the little blue trace on the pigtail), backflushed the system, and relocated the pisser. Finally, about two weeks ago (first run this season), the alarm went off and wouldn?t stop so long as the ignition was on.
I then started following wires, and discovered the problem. It turns out that in one area, the leads from the VRO tank were bundled together with supply wires from the battery. In most places, those wires were secured to the structure using Zap straps, but in once case, they were simply draped over a metal brace. Over time, and with vibration, the wires had rubbed through their insulation and were periodically shorting out, possibly due to viration at certain RPMs, or possibly due to changes in the amount of juice going through the charging system at higer RPM. I deduce that the problem got worse such that, two weeks ago, the short became permanent. I separated the wires, sealed up the rubbed sections with liquid electrical tape, secured them properly, and took her out for a spin. Went for an hour at full throttle with not a peep from the system (unheard of before now). Shorting leads to the block still produces the alarm, however, so it looks like the problem is licked.
What a relief. Most of the troubleshooting was done with guidance published in this forum, so my thanks to all.
I then started following wires, and discovered the problem. It turns out that in one area, the leads from the VRO tank were bundled together with supply wires from the battery. In most places, those wires were secured to the structure using Zap straps, but in once case, they were simply draped over a metal brace. Over time, and with vibration, the wires had rubbed through their insulation and were periodically shorting out, possibly due to viration at certain RPMs, or possibly due to changes in the amount of juice going through the charging system at higer RPM. I deduce that the problem got worse such that, two weeks ago, the short became permanent. I separated the wires, sealed up the rubbed sections with liquid electrical tape, secured them properly, and took her out for a spin. Went for an hour at full throttle with not a peep from the system (unheard of before now). Shorting leads to the block still produces the alarm, however, so it looks like the problem is licked.
What a relief. Most of the troubleshooting was done with guidance published in this forum, so my thanks to all.