Electrical Nightmares

[gavin]

Had a few problems recently with switches on our rib.At the throttle controls we have a pair of remote trim and tilt switches one for each Ficht 75 hp.One of these developed a short internally due to moisture ingress, then result of this was the ptt operating and driving one engine upwards, the only problem here is our motors hit the A frame before the tilt limiting cams switch the pump off, not good there is no quick fix to this additional problem as the cams are adjusted all the way out, we stopped the motor before any damage was done.I thought this was a once off problem however the other switch done the same about 3 weeks later, to overcome this problem I introduced inline safety switches in the circuit to break the power to the new trim tilt consul mounted switch in the event of this happening again, at least isolation was possible now.We had a lot of heavy rain in Dublin over the past week, and what happened next is rather disturbing.Our engine mounted trailering trim and tilt switch a very waterproff piece of switch gear devoloped a short internally this is an Evinrude switch, however it happened when we were not with the boat.The result of this piece of bad luck was the engine trimmed downards all the way and the ran the pump continously until the battery went flat.These units are not designed for hours of run on time as they develop heat, however we seemed to have been lucky, not so until I priced a new switch,Euro 140.I felt it again had to be moisture ingress even though this switch is waterproff and resin encapsulated, unserviceable, I simply filled a hypodermic needle with wd40 and forced oil tro the rubber cover of the switch and injected oil into the switch, this dispelled the moisture and the switch has worked okay ever since.The moral of this story is this , fit battery cut off switches to your boat as any component failure like our ones could cause problems especially if you are not there to deal with them, even normal ecectrical leakage in damp environments can be limited by incorporating suitably sized switches into your boat gavin

[Powerboat]

Hi Gavin,

The obvious solution ( which you have copped yourself) is to fit a master switch.

One small word of caution on Master switches !

It is very important to turn off all electric Lights , radios GPS's etc. ) before turning on / off the master switch .

Failure to do so can result in sparking within the Master switch .

I recently came across this in a Daily used RIB with a lot of electrics. They were going through a master switch every 6 months as sparking caused corrosion and burning inside the switch.

Best wishes ,

Stuart
www.powerboat.ie

[gavin]

Stuart you are right, but remember all the electrical loads in a rib are resistive ie lights, lamps pumps to a certian extent, and not inductive which helps life of switches and reduces the size they have to be,all switches in your house car etc are designed to cope with load and when not, they operate relays, the main switch on your domestic fuseboard can operate under load, for example, the biggest load on rib will probably be a starting motor remember batteries on board boats have cranking capabilites of several hundred amps for short spaces of time so it is really important to rate the switch correctly and incorporate some spare capacity into it.Another problem with current travelling through switches and battery switches is because we are using 12v dc systems in general to light a 100w lamp or spotlight we useabout 8 amps so think of what a starting motor pulls through a switch ,these are things often forgotten about when we are happily powering our ribs up and down waves, but you are right to limit the arcing in your main switch make sure you shed loads as far as possible before operating it, we have fitted battery switches with plastic inserts to limit corrison, as battery switches have failed on us before and we ended up bypassing them and then not replacing them as quickly as we should, not so wise but we have been lucky this time cheers gavin