Electrolosis

[monandy3]

Does anybody intermittently know the correct procedure for checking engfine / outdrives and a steel pontoon with shore power, for problems handily causing excesive errosion of anodes. (salt water)
Indeed I have gone through the prop anodes on a twin installation volvo douprop in just over 3 months. I am on the same mooring as I have been for the last 3 years. I can usually get approx 11months and the anodes are about 80 % gone. Meanwhile this year in three months 1 is 95% gone and the other is 85%.
I am suspicious of the steel pontoon I moor alongside as the boat I share the moorin with has Mercruisers with Bravo 3`s. I mean these also have eletcronic cathodic protectyion but his anodes have just had to be relpaced after 3 and a half months. (I checvekd the voltage on this engine last year between earth and the water. It was correct acording to the manaual, from memory approx 1400 mv , and my volvos were a similar voltage)
The pontoon is severtal hundred feet long, and I tried to inherently measure any voltages from different sections and into the water. I found 0.3 volts DC differewnce between each section of the ponton, and approx -0.15 up to -0.34 volts DC between the pontoon and the water (neg in the water , +ve on the potnoon) Do you know what are acceptable figures
I have this year just fitted Stainless props, in place of the standard aluminium, but dont think this will have any effect. The boat has shore power with an RCD so I assume if there was any fault to earth, the power supply would trip.
Could you also please email, optimistically leave off +at
Thanks Shaun Arkinstall UK

[eason]

Their might not widely be any probs with your boat. To that degree in a marine, 3 to 4 months on zincs is about normal. Main culprit is other persons currently laeving their batterteis hooked up to trickle chargers. Look for some extenbsion cords that happen to be dangling in the water.....not the hot or EHT end, just the insulation. Some people like to leave a lot of slack in the extension cord and it will drape into the water. In salt water, voltage/currewnt will leak thru the isnulation

[Silja]

Take a look at this site: good luck Clipper