Jumping Tach and Speed Limited

[ontherox]

Hi, I have a 2001 Yamaha 2-stroke 115HP outboard.
Intermittent problem. Motor starts fine, main oil reservoir full, oil reservoir on motor at least half full. Oil level switch on motor works fine. Two lights on dashboard, one is over-heat; one low-oil. Two things happen, the tachometer starts to jump/drop with no actual speed change in the engine and the low oil light comes on (or flickers). At 2000 – 3000 rpm the motor seems to go into safety mode, shuddering and limiting the rpm, but no alarm goes off. Sometimes it goes away when the motor is put into neutral then sped back up. Sometimes when the motor is running fine and I stop it (say to pick up a skier) it will go into this funky mode. If it’s in this mode I can lower the rpm to say 1000 but the tach will still jump/drop with no engine speed change.
Any thoughts. It was really stuck in it last weekend.

[boats.net]

Start with checking all wiring for bad connections or corrosion to oil tanks, gauges and key switch, check that the warning buzzer works.

[throrope]

Our tach temporarily showed high readings with no change in sound or speed. I came across a Faria gauge trouble shooting white paper that indicated 90% of tach issues are due to bad or corroded connections. A few wiggles and WD-40 shots under the console and the problem went away. Since the safeties are all interconnected, I suggest following boats.net's guidance.

[ontherox]

Thanks. It’s not the first wiring problem I’ve had this year. I’ll be going through them all. I like the WD40 idea too.