Mainship Mk1 check engine buzzer

[mgardner]

1979 mainship mk1 with Perkins. After 3 years had a buzzer going when under way.its behind below console panel. Drawings say it's engine buzzer with 2 inputs , water and oil. Never made a sound before. Oil level and engine temp ok. Topped up oil, approx 2 litres. Now it only buzzes when key on and engine off. It comes back on after shutdown when oil pressure drops off to approx 20 psi on gage. Anyone have this happen? I am thinking maybe it should be on when key is on until pressure builds up like an idiot light in a car. Could it have been stuck and started working normally?

 

[LaBomba]

I think you are right. It should start buzzing as soon as you turn the key and until the oil pressure comes up after starting. If it was buzzing while running your pressure was likely low. A very important piece of equipment IMO, you may want to check all the connections to it, maybe at the ignition switch??

 

[TowLou]

Agree maybe switch going if you are getting buzzing with the key off. Should get a buzz right when you turn key on and a buzz when you shut down motors before turning key off.


Edit:: thats as long as everything is ok when engines are running. If a buzz when running id be worried and checking more. Id say switch.

Twin screw? Is it one side that keeps buzzing when this happens?

 

[mgardner]

No buzz with key off

 

[TowLou]

Then all ok. Only if its buzzong when engines are running id be worried.

 

[diver dave]

Oil pressure switches are quite unreliable. The diaphram leaks internally and you get a false low pressure warning.

 

[AusCan]

That is the way it is supposed to work. The buzzer sounds when the oil pressure is low or coolant temperature is high reminding you to check engine as soon as possible.

There is no oil pressure when the engine is not running (and for the first couple seconds when the engine is started) so the buzzer will also sound with the key on.

No different from the oil light in your car.

 

[mgardner]

Think I have it figured out. Was doing work last week, found a wire off what I now know is the oil sensor. Put it back on figured had just knocked it off. It had fallen off again and was touching ground hence the continuous buzzer. With it now on the switch proper it works as intended. The buzzer has keyed power all the time and gets grounded either through the oil or temp switch. Now that I know what's up I am going to upgrade circuit with individual lights for coolant and oil plus mimic the lights and buzzer on fly bridge.