volvo 2002 18hp,two pole electrical system with relay -earth

[jmuir1]

Hi
Have the above engine. Have a relay below starter motor that battery earth joins to. Question is what is the point of this, I understand this is a 2 pole system, again what does this mean. Engine is on Westerly Fulmar therefore is not a sail drive type. Also boat was reengined apparently at some time


John

 

[VicS]

See the recent thread at http://www.ybw.com/forums/showthread.php?t=254518

In there is a link to the owners manual that shows two different wiring diagrams.

Looking only at the engine wiring ( not the control panels)

The one on page 19 shows what I think you have with an earthing relay.

The other on p20 shows the setup without ( also reproduced in the same thread by pvb)

The engine is wired without using the block as the common negative.
The alternator negative is insulated and all the warning lights and, if fitted, instrument sensors have a negative terminal instead of using the block as negative.

HOWEVER the starter motor does not have an insulated negative.
Therefore while cranking the engine the cylinder block must be connected to the battery negative. This is done with the additional (earthing) relay which is energised during that time.