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Hello again, you may have seen my recent post relating to the fact that I am due to take delivery of a 33’ Sea Otter in the coming weeks. The boat looks spotless, and such is the demand at the moment that I am going to have to wait ages to get a survey done, so I wasn’t going to bother. But then today someone told me that they can suffer from pitting of the aluminium. Does anybody know if this is true or not please? Thanks in advance. Andrew. 

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I think that concern is mainly around galvanic corrosion if the boat has been sat on shore power without any galvanic isolation. Aluminium would be very susceptible to this form of pitting/ corrosion in that circumstance. Otherwise it's shouldn't be an issue.

 

Does the boat have a galvanic isolator or even isolation transformer?

 

Edit: You say you might not bother with a survey. I think that might be a mistake

Edited by blackrose
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Thankyou blackrose. The honest answer is that I don’t know, but since it is only one owner and it has been their pride and joy, then I would certainly assume that it does have one fitted. I will check though. Thanks again. 

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1 minute ago, ARAL said:

Thankyou blackrose. The honest answer is that I don’t know, but since it is only one owner and it has been their pride and joy, then I would certainly assume that it does have one fitted. I will check though. Thanks again. 

 

Check it has one fitted, find out the model and ask if you can go and test it's working. The test shouldn't be difficult to perform.

  • Greenie 1
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8 minutes ago, ARAL said:

Thankyou blackrose. The honest answer is that I don’t know, but since it is only one owner and it has been their pride and joy, then I would certainly assume that it does have one fitted. I will check though. Thanks again. 

 

Of course if they've never been on shore power then they might not have fitted one and that's perfectly acceptable. 

 

The other thing to check is that the hull is bonded to the boat's mains earth. If not then there's no need to worry about galvanic corrosion because the hull is isolated, but that would raise a different concern regarding electrical safety.

 

 

Edited by blackrose
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7 minutes ago, blackrose said:

 

Check it has one fitted, find out the model and ask if you can go and test it's working. The test shouldn't be difficult to perform.

Thanks again, blackrose. You’ll have to pardon my (all things electrical) ignorance, but how exactly would I go about testing the galvanic isolator if there is one fitted? 

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It might be worth your while , Aral, joining the Sea Otter Users Club and asking about pitting there. 

 

haggis

Edited by haggis
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8 minutes ago, ARAL said:

Thanks again, blackrose. You’ll have to pardon my (all things electrical) ignorance, but how exactly would I go about testing the galvanic isolator if there is one fitted? 

 

It may depend on the model. On my old one I could use the diode setting on a multimeter to check the reading in both directions. I could also use a 9v battery to force the diodes into circuit and check the led status monitor.  On the new one I have you can take an ordinary AA 1.5v battery and connect it to the terminals of the. GI which again forces the diodes into conduction and is shown on the status gauge.

 

All done with shore power disconnected.

2 minutes ago, haggis said:

It might be worth your while , Aral, joining the Sea Otter users group and asking about pitting there. 

 

haggis

 

Yes that's a good suggestion.

Edited by blackrose
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1 minute ago, blackrose said:

 

It may depend on the model. On my old one I could use the diode setting on a multimeter to check the reading in both directions. I could also use a 9v battery to force the diodes into circuit and check the led status monitor.  On the new one I have you can take an ordinary AA 1.5v battery and connect it to the terminals of the. GI which again forces the diodes into conduction and is shown on the status gauge.

 

All done with shore power disconnected.

 

Yes that's a good suggestion.

Thanks haggis. Is that a group on here, or a separate entity?

Just now, ARAL said:

Thanks haggis. Is that a group on here, or a separate entity?

Thanks blackrose, but you may as well have just tried to tell me how to build my own rocket! 😊 I’ll ask the engineer to look into this. 👍🏼

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It's a separate entity.

 

I'd definitely get a survey for this and also other reasons such as physical hull wear. However, I'd still find out whether the boat has a GI but if not and you know that the boat has been on shore power for a while then that might even induce me to walk away and save the money on the cost of the survey.

 

Some people don't know about galvanic corrosion so the owners might not know if they have a GI fitted. I'm sure the builders would have fitted one on an aluminum boat, but the thing is to make sure it's still working.

 

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24 minutes ago, ARAL said:

Thanks haggis. Is that a group on here, or a separate entity?

3 minutes ago, ditchcrawler said:

@haggis have you got a GI fitted by the builders?

 

 

Aral it is a separate web site at https://www.seaotterowners.org.uk/

 

Brian, no gamebird doesn't have a gI but we have never been connected to shore power or near a boat which was.

 

Haggis 

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1 minute ago, haggis said:

Aral it is a separate web site at https://www.seaotterowners.org.uk/

 

Brian, no gamebird doesn't have a gI but we have never been connected to shore power or near a boat which was.

 

Haggis 

I wonders from comments made by others if it might be a standard fit. When did Sea Otter go out of production?

 

 

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1 hour ago, ARAL said:

Hello again, you may have seen my recent post relating to the fact that I am due to take delivery of a 33’ Sea Otter in the coming weeks. The boat looks spotless, and such is the demand at the moment that I am going to have to wait ages to get a survey done, so I wasn’t going to bother. But then today someone told me that they can suffer from pitting of the aluminium. Does anybody know if this is true or not please? Thanks in advance. Andrew. 


Yes this has been reported on Sea otters. It's not that common and if it has happened it is very visible on the waterline. Definitely get it surveyed, as some of them might never have been out of the water.    

Edited by booke23
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4 minutes ago, ditchcrawler said:

I wonders from comments made by others if it might be a standard fit. When did Sea Otter go out of production?

 

 

I think it became a standard fit  (gamebird was probably built before GIs became common) and I have no idea when Sea Otters went out of production - it was a long time ago though 🙂 

 

haggis

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Its is more than worth the cost of fitting a GI on an Aluminium boat.

 

Remember that Aluminium is used as a sacrificial anode in Brackish water, as it sits alongside Zinc and Magnesium (both used as anode material) and is considerably less noble than steel. When alloyed (as per the Sea Otter boats) the nobility is even lower and is just above Magnesium.

 

If you don't protect it it will erode the hull away whilst protecting the steel components (shafts etc).

 

 

 

Galvanic Order of Metals A - C 2.jpg

Edited by Alan de Enfield
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6 minutes ago, Alan de Enfield said:

Its is more than worth the cost of fitting a GI on an Aluminium boat.

 

Remember that Aluminium is used as a sacrificial anode in Brackish water, as it sits alongside Zinc and Magnesium (both used as anode material) and is considerably less noble than steel. When alloyed (as per the Sea Otter boats) the nobility is even lower and is just above Magnesium.

 

If you don't protect it it will erode the hull away whilst protecting the steel components (shafts etc).

 

 

 

Galvanic Order of Metals A - C 2.jpg

Thanks Alan. I will ask the question of the vendor, and investigate (much) further if there is not one present. 👍🏼

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