Outdrive corrosion

[jackmorgan]

I have a 2007 four winns vista 258 with penta dps-a outdrive. It's only ever seen fresh water but there seems to be significant corrosion on the pivot housing. There is zero corrosion on the upper / lower gear housing. I have attached a photo. I believe the anode that sits under the transom assembly is to blame ... It looks brand new and has yellowed, whereas the anode on the drive itself shows some corrosion). My question is, if i replace the transom assembly anode, will this stop further corrosion (mostly anyway)? Or should I paint everything exposed asap? Thank you.

Jack

 

[gm280]

jm, seems the corrosion is only on that one section. Maybe the manufacture didn't do a good job with the priming painting process with that part. I would clean all the corrosion off, and any exposed metal should be primers properly and repainted. JMHO

 

[bajaunderground]

Do you have VP's active anti-corrosion set-up (EVC)? Aluminum and stainless steel do not like certain water types and expedite corrosion when together...or so I'm told.

If you have it, check and make sure it's 100% opperational?

Also, errant electrical current can cause accelerated corrosion. Do you slip?

 

[Horigan]

You also need to make sure the anode has a good electrical bond with the part you're trying to protect. I had a same issue with the lower unit anode on mine due loose bolts and insufficient prep of the mating surfaces. I also add dielectric grease to the joint to help maintain the bond.

Rich

 

[Thalasso]

Look and see if the bonding strap/wire is connected to the hose clamp. The clamp is connected to the dc bonding buss by another wire. All metal things must be bonded to d/c

 

[Scott Danforth]

I agree with Thalasso, my guess the bonding wire is missing

 

[frantically relaxing]

I think you may have some DC stray current corrosion going on, I notice the corrosion is most apparent around sharp edges, which is exactly where stray current corrosion occurs most, path of least resistance electrically. The outer edge of that ram is a good example... Unfortunately for me, I'm all too familiar with this problem, as our houseboat was victimized by this.

In glass boats, the most common culprit is the bilge pump, with it's hot 12v wires sitting in bilge water. The hot can energize the ground thru the water, stainless thru-hull fittings are prime targets, especially if they're not bonded. Once this happens, all electrically grounded metal in the water is now a conduit for the electric current as electrons leave the boat looking for ground. And every electron takes some metal with it. It doesn't take a lot of voltage either, I've read where 1/2 volt of DC power can destroy an outdrive in a month.

Check your bilge pump and like the others have mentioned, make sure all your grounds are as they should be.

 

[jackmorgan]

Do you have VP's active anti-corrosion set-up (EVC)? Aluminum and stainless steel do not like certain water types and expedite corrosion when together...or so I'm told.

If you have it, check and make sure it's 100% opperational?

Also, errant electrical current can cause accelerated corrosion. Do you slip?

I don't have the EVC setup. I do have a slip and there are quite a few older boats around me.

 

[jackmorgan]

Look and see if the bonding strap/wire is connected to the hose clamp. The clamp is connected to the dc bonding buss by another wire. All metal things must be bonded to d/c

So there should be a wire connected to the pivot housing itself? There are hose clamp wires on the bellows clamps, but that would only protect the clamps i'm assuming - the rubber bellows would insulate it from any other parts.

 

[bajaunderground]

...then check as suggested...you will still have grounding straps and might have some stray electrical current. If it's your boat, then it's an easy fix...if it's shore power or another's, might be tricky tracking it down?

 

[Thalasso]

So there should be a wire connected to the pivot housing itself? There are hose clamp wires on the bellows clamps, but that would only protect the clamps i'm assuming - the rubber bellows would insulate it from any other parts.

There should be a wire running from the housing to the clamp on the bellows which the wire runs to the transom housing.

 

[drewm3i]

Check the ground wires.

 

[lg260ss]

If you are in freshwater you need to be using magnesium anodes. Volvo's active corrosion system is not effective in freshwater, in fact if you have it and you are in freshwater you are supposed to disconnect it. Magnesium anodes are very important, that is what needs to be done first. Your anodes turning yellow is a sign that they are zinc.

http://www.volvopenta.com/volvopent.../parts_service/faq/Pages/FAQ_corrosion_1.aspx

 

[Horigan]

Wow! I never heard of that. Can I assume the anode material selection being a function of fresh or salt water use is not unique to Volvo? Should we be following the Volvo material recommendation for other drives, like OMC?

 

[lg260ss]

Wow! I never heard of that. Can I assume the anode material selection being a function of fresh or salt water use is not unique to Volvo? Should we be following the Volvo material recommendation for other drives, like OMC?

Yes, those recommendations are across the board.