89 johnson 50hp alarm help

Im getting a random alarm running WOT only. It doesnt do it every time and sometimes it will quit by just backing off the throttle some. A time or two ive went to N and shut the motor down. Restart immediately and no alarm.

History : I replaced the pump and all L/U seals last year thinking a week pump was causing the alarm. The impeller was on its last leg for sure but all still intact.

The alarm is very spurratic. Its not going off every time I hit the gas, more like once or twice a day only at WOT, every few trips out

Im guessing I have a thermostat sticking and I will replace them when it warms up a bit just for good measure. Havent physically checked them, just kept fishing . If it were really overheating the alarm should be constant, corect?

any openions from the more experianced marine mechanics on here

VRO was removed long before I baught this boat so we can rule that out

ive got a 85 hp Johnson on mine alarm was going off but peeing good I unplugged temp wire and it quit so I tried impeller it fixed it sometime if they set in one spot for awhile the blades on impeller kinda stay bent and don't pump enough my .02

Thanks for the reply bud. Impellers only got about 4 hours on it so I can rule that out

If the VRO was removed , what are you running for an oil tank ? There is an oil level sender ,and it may be what is causing the alarm if it is still connected ! Need more info !

Oil tank was removed, I've never found the Sensor wires, I'm guessing they cut and spliced on the motor. I'll have to hunt a wiring diagram to figure out what wires I'm looking for. Nothing loose in the bildge and all wiring around the motor looks factory ( no cheap butt connectors and electrical tape)

Any in site on what color or where the oil level Sensor wires come from?

I've had the boat over 3 years btw

Not sure this will help but don't hurt to have it
Tim

I know this is an old thread, but mine was doing the exact same thing. Noticed fuel wasn't getting to the filter on the motor, new fuel lines and tank fixed it right up.

My bet is that it is the fuel vacuum alarm, which operates on same alarming circuit as the heat alarm less there is a diode that prevents triggering the SLOW operating mode (which messes up tming intentionally so you can't run it fast).

The vacuum alarm triggers in cases where fuel draw is less than designed.

As other posted said, check/replace your fuel delivery side of the system, including any fuel pickup if running from a fixed tank. I've seen clogged filter screen on PUs cause this too.

The 50hp has no fuel vacuum switch.

Pappy said:

The 50hp has no fuel vacuum switch.

Click to expand...

DOH ... then I stand corrected ! Thanks Pappy!

So what maybe causing his alarm then?

I will tell you that back in that era we had a bunch of hot horn failures.
The common failure mode was a faint horn sound.