Man D2848 LE403 coolant level alarm.

Hi ok so little update
The black boxes that Mapism mentions are there with the small boxes on the side that deal with sensors. When the ignition is turned on the 3 lights light up red. One shows you have a temperature sensor the other two are depending on if you have one or two level sensors. What ever is connected and working turns green so on my good engine I end up with 3 green lights. On my bad engine I end up with only one green light for my temperature. Even with the sensors not connected they turn green on my good engine. But not on my bad engine they stay red. Is the problem somewhere else. Will carry on trying

Stbd engine ?
but that’s doing what it should
turn key
Alarm sounds light comes on 2-3 seconds later alarm stops light goes out
In engine room lights on sensor box change from red to green and engine starts

Port engine
Turn key
Alarm sounds light comes on and stays on. Alarm sounds continuously
In engine room lights on sensor box stay red
Engine starts fine.

No change weather the sensors are connected or not same result. So NOT sensors.

Alarm monitoring circuit board I take it behind the dash
I have checked the wiring behind the ignition keys and all seems fine
Checked behind the alarm light panel with all the alarms on. All seems fine no loose wires or frayed bits moving behind the dash next.

Please keep going guys all ideas welcome and I will work through them lol.
Man engineer says it’s an electricians job.
Electrician says it’s an man engine problem grrrrrrrrhhhhhhhhhhh !!!!!,,,,,,!!!,!,

Hi mapism
No I realise that but I am happy there is coolant. I don’t want to use the boat but do want to sort the problem out.
I do keep thinking the problem lies in the black sensor box on the side of the larger box. But can’t even find out who makes them to buy a new one. I’m slowly working my way through the boat. But then remembered I will have to do the same at the flybridge controls lol doh !
Also woke up wondering if it’s the stop switch that is causing the problem ?
I’m in danger of this problem taking over my life because I hate it when I can’t work it out.

Correct

Ok quick update to all you good people who have tried to assist with this one.
Think we may of found the problem. I had a marine electrician onboard doing a quick job for me who said he would have a quick look and see if he could do anything for me whilst I was at work in relation to this.
Turns out he only worked for sunseeker as an electrician, how lucky.
Anyway he did much the same as I did from one end to the other. When he removed the small black electrical sensor box out came some water. From where who knows but it’s looking like that could be it. Just waiting for prices now and he is going to see if he can repair my one. Fingers crossed

Yes the smaller one on the side with the lights. As per your picture. I have had one quote for a replacement of $800. It’s literally a small pcb and not much else. Will update once it’s sorted.

No not really although this could be it. On a 2002 Sunseeker manhattan56 on the port side in the saloon is a vertical sliding electric window when it opens it slides down into its own fibreglass box. This box has a small drain hole in it and hose which connects to the drainage system. This allows any water when washing down or raining and goes down past the window rubber to drain off. Last year during winter my drain plug got bunged up ? So the bin filled with water and over flowed. This is more or less directly above where my port black box is. It’s all I can come up with I’m afraid. My engine room is otherwise always dry and I did some changes to the window bin and it’s fine and doesn’t do it anymore.