New Alu boat - hull & anode questions

So, I picked up my first brand new aluminimum boat and am looking for a little advice (had an old glass boat before). First use was on the water for a weekend 3 days/2nights straight. Pulled it out after and gave it a good clean with salt away. After this one outing I've noticed a pronounced water line, below that it is discoloured and has heaps of salt pits I cant seem to remove. Seems strange that the flap (which is isolated on plastic hinges) isnt discoloured at all though.  Also the anode has copped a bit of wear from this one use.

Is this all "normal" ? Just keen to get an oppinoin as I dont have alot of experience with ally boats. Thanks a million!

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Posts: 292

Date Joined: 22/05/19

Yeah I believe so. On my

Sat, 2019-10-19 05:25

Yeah I believe so. On my plate unless I spend heaps of time washing it down, I allways get a couple salt crystals pop up on the hull. You will think that you got it all off but you never do hah. You could allways shammy  it down after but no point being a plate boat. The ally will produce it  down protective coating on it. Maybe check the wiring and make sure they have not used the boat as an earth that will rapidly eat away at the hull I believe ( if wrong please let me know). But with the anode I’m unsure about that. Could be a cheapo and quality may not be the best but at least you can see it doing its job. Maybe have a look at another anode and swap out and see the difference. 


Hope it helps but looks like a quailty built boat and the welds look clean too. Who built and and what size is it mate?

Posts: 82

Date Joined: 07/12/13

Couple of Questions.

Sat, 2019-10-19 09:17

What is the flap? What does it do?

Looking at the anode it appears to be "insulated" from the boat through via plastic backing. Correct me if I'm wrong but shouldn't the anode be the "ground or earth" for any energy to dissapate and be connected directly to the hull.

I have an aluminium boat and are curious as to do anodes protect the hull or have any effect at all?

Posts: 292

Date Joined: 22/05/19

Nah never make the boat the

Sat, 2019-10-19 11:54

Nah never make the boat the ground on an ally boat.  Always back to the neg  

Posts: 82

Date Joined: 07/12/13

Sorry for the confusion. Yes

Sat, 2019-10-19 12:57

Sorry for the confusion. Yes all the boat electrics and electronics should be insulated from the hull. I'm talking about the anode only. Should it to not be fixed directly to the hull? Direct contact between the aluminum and the zinc anode?


Swompa's picture

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Date Joined: 14/10/12

 Anode should be directly

Sat, 2019-10-19 19:20

 Anode should be directly against the hull with nothing insulating it.

gillyL's picture

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Date Joined: 26/04/14

 looks like a bar crusher and

Sat, 2019-10-19 12:38

 looks like a bar crusher and the flap looks like the inlet to flood the cavity below deck for ballast

Posts: 4

Date Joined: 22/04/13

 Yeah correct it is a

Sat, 2019-10-19 15:02

 Yeah correct it is a barcrusher with ballast flap.  Anode is bolted with 4 bolts into the motor bracket with another stainless earth strap too, the plastic is the motor mount. All electrics are earthed to a common insulated earth stud, but the motor is of course attached to the hull so the hull is grounded.

Guess I was suprised more than anything that the anode had so much wear from a short time in the water... also the staining of the hull and salt, but not the on totally insulated flap is also strange to me.

carnarvonite's picture

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Date Joined: 24/07/07


Sat, 2019-10-19 15:12

 Sound like there is an earth current running through the hull by the amount of electrolisis that has occurred. If I was you I'd be looking for something directly earth to the hull and not to a cable running back to the battery

Posts: 292

Date Joined: 22/05/19

My mate bought a crushed and

Sun, 2019-10-20 06:50

My mate bought a crushed and his engine was earthed to the hull which was doing exactly what looks like on your transom  

still trying's picture

Posts: 428

Date Joined: 27/06/17

 That does seem like a lot of

Mon, 2019-10-21 10:32

 That does seem like a lot of action for a short time period. Sorry but I don't mean to hijack your thread but reading some of the comments here I'm not sure I have correctly installed my voltage rectifyer regulator on my motor it is just a pull start on a Ali dinghy and I took the black wire and earthed to the motor and from that earth back to the negative on the battery does anyone know if that is correct? 


 rather be fishing