Yamaha 70HP 2ST Electrical Issue

[Zelda]

Afternoon All,

First proper trip out this season yesterday - Hamble to Christchurch. All went smoothly on the way there, however midway through the return journey I noticed that the Yamaha Multifunction gauge had gone blank and the fuel gauge was reading end stop zero. The engine did not miss a beat.

Was reluctant to investigate at sea, as unsure if I stopped the engine that I would be able to crank. Once at the Hamble jetty I gave a cables under the console a wiggle but nothing happened - not even a flicker on the fuel gauge. However as soon as I switched the engine off and back on again both gauges immediately came back to life and I could not make them fail again.

I am an electronics engineer by trade so really should be able to troubleshoot this one, however before I waste a perfectly good sailing Saturday afternoon on it, I wondered if these symptoms sounds familiar to anyone? Doesn't feel like the usual loose under-console wiring - more like an engine relay maybe...

(Yamaha 2ST 70HP 2005 with digital multifunction gauge)

Regards,

Rob

[spartacus]

Where to start.

Yamaha, in fact all marine outboard manufacturers don't use tinned cable. Now it could be as simple as corrosion and a break in continuity but the fact it reset itself when you restarted, either points to the ignition wiring in the throttle box, wiring from the battery to a bus bar or similar or indeed the guage itself.

Have a look at the cable ends. When they are on their way out you'll see oxidisation and the copper turns green. You can wire up a continuity signal on a multimeter just to rule that out. A light sand with emery paper on the cable ends just buys you time. Rather than replace the entire loom you can strip-in some tinned cable. I'm sure the instrument loom joins the main loom tonthe engine via bullet connectors. Pull them apart, check the connectors, lightly sand and reconnect.

There also the instrument itself. If it was new with the engine, then we're talking 16 year old tech, so an intermittent fault isn't unheard of.

It's difficult to pinpoint - but hopefully that's given you some pointers. Also look at the wiring loom on the engine.

[Zelda]

Thanks Spartacus. The Fuel gauge is seperate and not a Yamaha one and that also failed, so that cuts down the possible failure modes a bit...

Regards, Rob

[spartacus]

Originally Posted by Zelda

Thanks Spartacus. The Fuel gauge is separate and not a Yamaha one and that also failed, so that cuts down the possible failure modes a bit...

Regards, Rob

It's like a case for Columbo! If both gauges went down (and one isn't Yamaha) then that narrows it down to electrical +tive and -tive to provide the circuit, either from the ignition loom on the remote or bus bars, and not the sender wiring to the gauges.

The engine will continue to run with the battery isolator switched off, but you wont be able to restart - but I take your point that things go through your head when you get wiring issues.

Anyway - keep us posted as to the eventual outcome.

[Zelda]

Yes, my understanding is that lot of engines will continue to run with the battery isolated if not disturbed - which is why I decided not to troubleshoot at sea 8-)