Electronic Leak Testing

[olly_love]

We have a Yanmar 2gmF with a Saildrive,

Brand new prop 2 months back with anodes on the prop,
the shaft anode was in good condition

but.... we now have pitting all over the prop and the anodes have gone!.


We are on a mooring mid steam in the hamble with no power generation onboard. And have the batteries isolated with nothing left on at all ( not a bilge pump etc)

We left the boat for 2 months and when it came to a lift out its pitted?

The sail drive leg has gone the same way



HELP!,



Hows the best way to test for an electrical leak? Im amazed if there is one? Or could it be another boat causing us an issue.

 

[Alex_Blackwood]

We have a Yanmar 2gmF with a Saildrive,

Brand new prop 2 months back with anodes on the prop,
the shaft anode was in good condition

but.... we now have pitting all over the prop and the anodes have gone!.


We are on a mooring mid steam in the hamble with no power generation onboard. And have the batteries isolated with nothing left on at all ( not a bilge pump etc)

We left the boat for 2 months and when it came to a lift out its pitted?

The sail drive leg has gone the same way



HELP!,



Hows the best way to test for an electrical leak? Im amazed if there is one? Or could it be another boat causing us an issue.

You don't say if there is shore power available on your mooring, I suspect not in mid stream, but. Simple answer is that it could be caused by an adjacent boat but there would have to be a power source. Either shore power or from the other vessels system. No easy way to check for electrolytic action which is what you probably have. There are cathodic protection checks that can be carried out using special anodes. Unless you know what you are doing you need a specialist to do this. For electrolytic action between the two boats you would need to inspect the adjacent vessel(s). Sorry if that is not of much help.

 

[VicS]

You don't say if there is shore power available on your mooring, I suspect not in mid stream, but. Simple answer is that it could be caused by an adjacent boat but there would have to be a power source. Either shore power or from the other vessels system. No easy way to check for electrolytic action which is what you probably have. There are cathodic protection checks that can be carried out using special anodes. Unless you know what you are doing you need a specialist to do this. For electrolytic action between the two boats you would need to inspect the adjacent vessel(s). Sorry if that is not of much help.

For it to be due to an electrical problem with an adjacent boat wouldn't there have to be a connection between the two boats to complete the circuit , one half of which is through the water.

 

[olly_love]

Hi, We are not plugged in and batteries were off fully ( 2 batteries with a rotary isolator)No power on the moorings,
im starting to think its mercury Marina Causing the issue

 

[BabaYaga]

Hows the best way to test for an electrical leak? Im amazed if there is one?

If it is the best I do no know, but you could try with all loads off to take away the positive battery clamp and measure for mA between post and clamp.

 

[VicS]

If it is the best I do no know, but you could try with all loads off to take away the positive battery clamp and measure for mA between post and clamp.

Good idea but you would have to do this while the boat is in the water

 

[Alex_Blackwood]

For it to be due to an electrical problem with an adjacent boat wouldn't there have to be a connection between the two boats to complete the circuit , one half of which is through the water.

Yes, that is why I asked if there was shore supply available on his mooring. Don't even know if it is a pile mooring or pontoon or what.
To answer BabaYaga He needs to have a connection to "Earth" We don't know his set up i.e. Does he have a GI?

 

[BobnLesley]

Do you have an automatic bilge-pump switch wired direct to your battery - on even when all is shut down?
If yes, check that; we had a Water Witch float switch go tits up and I was slow to spot the problem, it quickly caused a lot of damage.

 

[vyv_cox]

Unlike Volvo saildrives, Yanmar ones are not isolated from the engine and rest of the boat. It would seem that you have an earth leakage somewhere. As suggested by BobnLesley an automatic bilge pump is a possibility.

 

[billskip]

Unlike Volvo saildrives, Yanmar ones are not isolated from the engine and rest of the boat. It would seem that you have an earth leakage somewhere. As suggested by BobnLesley an automatic bilge pump is a possibility.

Also dont rely on total disconnection by the rotary switch, this maybe only disconnects one side, and as said above maybe an auxiliary designated supply remains connected

 

[BabaYaga]

To answer BabaYaga He needs to have a connection to "Earth" We don't know his set up i.e. Does he have a GI?

My suggestion was made on the assumption of no AC present, that is the problem being DC related.

 

[Alex_Blackwood]

My suggestion was made on the assumption of no AC present, that is the problem being DC related.

Appreciate that. When I say "Earth" I am referring to a connection to the water via the engine or anode etc. from the dc system (-ve)?.
Also for other posters he says "No Bilge Pump" As I have said previously this is something that needs looking at locally as no conclusion can be determined from the information available.

 

[anoccasionalyachtsman]

These might be silly questions, but if there were a leak from a nearby source, can it be measured by looking for Volts between the outstretched electrodes on a meter? Might it be better to extend the leads to a couple of metres each to get a more tangible reading? And if either answer is yes, then might rotating the electrodes (eg they're hanging off the bow and stern of a boat) indicate the direction that the source is wherever the boat is pointing when a maximum V is indicated? (Or the reciprocal, and maybe someone who remembers more of the school stuff will remind me which way current goes wrt +/-, and so which way to look).

 

[olly_love]

Thanks all
So no bilge pump
We are a race boat so all stripped
No ac power
No gi
The batteries (2 off) are on a simple 4 way isolator

Mooring is a pile with pontoon nr mercury marina with no power

 

[VicS]

These might be silly questions, but if there were a leak from a nearby source, can it be measured by looking for Volts between the outstretched electrodes on a meter? Might it be better to extend the leads to a couple of metres each to get a more tangible reading? And if either answer is yes, then might rotating the electrodes (eg they're hanging off the bow and stern of a boat) indicate the direction that the source is wherever the boat is pointing when a maximum V is indicated? (Or the reciprocal, and maybe someone who remembers more of the school stuff will remind me which way current goes wrt +/-, and so which way to look).

Conventionally current flows from + to -. In practice electrons flow in the opposite direction.
In an electrolyte (eg sea water) cations flow in one direction (+ to -)and anions in the opposite direction.

How do you explain the corrosion of the op's saildrive by a leak from another source?

 

[anoccasionalyachtsman]

How do you explain the corrosion of the op's saildrive by a leak from another source?

I don't begin to Vic. just picking up on Olly's suspicions about the nearby marina.

 

[Alex_Blackwood]

I don't begin to Vic. just picking up on Olly's suspicions about the nearby marina.

Once all the theory is exhausted. The bottom line is that something has eaten his anodes and pitted the prop. I would be looking at how close his stern gear is to the Pile or any metal associated with the pontoon. I know the theory is that there should be a connection between the two and through the water to form a "CIRCUIT" However, I would love a penny for time I have heard it said "That cannot happen" etc. I would also be suspicious of any other boat on the pontoon and what his electrical system is doing. Especially if in close proximity or moored stern to stern. What has changed since changing the prop? I think Sherlock Holmes said something about eliminating the obvious and seeing what was left!

 

[Wing Mark]

Thanks all
So no bilge pump
We are a race boat so all stripped
No ac power
No gi
The batteries (2 off) are on a simple 4 way isolator

Mooring is a pile with pontoon nr mercury marina with no power

I would be checking for electrical connection between the keel (llead or Iron?) and the sterndrive.
I'd guess you have some bare metal on your keel and your saildrive is acting as its anode.

Or, do you have conductivity between the piles and the engine etc?
Moored with chain and the forestay connected to the rig connected to the engine somehow?

 

[Oily Rag]

And clutching at straws......check that you have the battery terminals the right way round. Negative "earth".

 

[olly_love]

So a little investigation today
We have a very small maintained supply but that’s all isolated now, but that’s also been there since 2004!
Checked all connections etc all good
There is 0ma or volts at the engine end when isolator is off
And the keel has nothing bar the keel bolts

few others around us have had the same issue but the serverity is what worries me, it’s eaten 2 button anodes and 1 sail drive

next path is to get the HM to contact all owners around us and see what they have had and if we have anyone new.

it’s all odd asit seems to have happened since we installed the new prop