Volvo saildrive electrical isolation

[paul]

I have a Volvo saildrive which I understand is supposed to be electrically isolated from the engine (a MD22). When I connect a multimeter between the saildrive unit (the bit inside the boat) to the engine I get continuity. Is this right or should it be isolated? Is it just the bit of the leg that's under the boat/water that's isolated or should it be the whole leg? How does it achieve the electrical isolation? Any advice would be appreciated. Thanks. Paul

 

[Gypsy]

My Volvo/Saildrive is not an MD22 (it's a D2-55) but it is isolated. Measuring with a multimeter when the boat is in the water can be misleading as the water has conductivity. On mine you can see plastic/teflon/dunno shims under the bolts which hold the saildrive/gearbox to the motor. I have measured as low as 8ohm and more often 100-200ohm but it depended upon location. Lower in marinas, high or infinity at anchor in a clean Turkish bay...BUT.. when hauled out always infinity. Apart from water conductivity there must be other electrolysis issues going on in marinas to influence the simple multimeter.

 

[crisjones]

I agree with Gypsy about the boat being in the water.

You can only really test the isolation when the boat is out of the water and dry. I have D2-55 engines with isolated saildrives and a multimeter will correctly show very high resistance when the boat is dry. When testing in the water you get very variable readings that are totally misleading.

 

[bendyone]

Sails drives are isolated from the -ve by means of a solnode by the -ve connection. It is only connected when the engine is running.

 

[Gypsy]

Perhaps you can tell us the motor model where you have seen that. As mentioned the Volvo D2-55s certainly have a physical isolation system in place at all times.

 

[bendyone]

we had it on 2 volvo 2001.

 

[Slowtack]

What about them thar bolts connecting engine and saildrive together?

 

[VicS]

You have put this question on Reader to Reader as well. Double posting is against the rules.

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