Aluminum Pontoon in Saltwater

[farawayinn]

Hi, just bought a used pontoon boat - Sylvan 20 ft year 2000. Original factory wiring, with only docking lights added by previous owner.

Two questions:

1. Should an aluminum hull pontoon (to be docked long term in saltwater) have a sacrificial zinc or magnesium anode attached to one or both hulls?

2. Should the wiring negative be grounded to the hulls?

The boat has a single battery, charged only by the outboard alternator, no shorepower at all. Wiring is currently run directly to the battery terminals, very messy. Will be adding second battery, switch, buss bars and probably an acr. Outboard is Johnson 2 stroke with typical zincs.

My assumption is yes on the first question, no on the second. But would really like some insight from anyone who has experience with small aluminum hull boats or pontoons docked in saltwater.

Thank you.

[MikeJohns]

Zinc anodes on both pontoons, and the pontoons should be epoxied too.

Bonding is a bit more complex and there are many pros and cons. If the outboard leg is bonded to the hull it will be protected by the hulls anodes, if the alternator or starter is grounded to the chassis (most likely) then you will then have a chassis bonded negative.

The Alternative is to fully isolate the motor protect it with its own anodes and run all systems unbonded otherwise the outboard anodes tend to get depleted by the hull, unless you stick some aft close to the motor.

Either way works well enough, but it is important to closely monitor things for a start particulalrly the outboard anodes.

I hope this gives you an idea.

cheers

[farawayinn]

Thank you very much for the advice. Have mounted zincs on both logs, also on center bracket. Will monitor condition closely. Motor tilts clear of water when at dock and electrical system is completely isolated from chassis, will keep it that way. Dealer's shop did a nice job on barrier coat under trilux33 bottom paint.

[augustwinds]

Can you please tell me what type of barrier coat was used? I am considering buying a pontoon boat for use in salt water in NJ and have been told that electrolysis will be a problem. I am hoping that using zincs will be enough but wanted to find out more about barrier coats too.