Saildrive Protection - EUREKA! or waste of time & $$

[grjfield]

I'm wondering whether anyone has ever thought of isolating their saildrive in order to prolong the saildrive zincs, as well as inhibiting growth on the prop. Over the winter both hard and hairy creatures set up housekeeping on my prop, requiring a short dive to scrap them off. As well the fun task of replacing the saildrive zincs will soon rear its ugly head.

The thought occurred to me to protect the saildrive by fashioning a large watertight cup to sit under it..making gentle contact with the hull. By making the cup slightly buoyant, and flooding the cup with freshwater via 2 tubes up to the deck, I may be able to evict the little critters and at least forestall the effects of zinc deterioration.

The partying creatures dont bother me much as it involves a fun 1/2 hour dive. However, solving the zinc deterioration would save $$$ (haulage, zincs from England for the Sillette saildrive).

Has anyone ever considered this, or tried to fashion a saildrive protection device (other than zincs)?
...or am I delusional with way too much time on my hands!

I would welcome any comments, both pro and con, on the idea.

regards
Chill E Bear

[deluxe68]

Why do you have to haul the boat to change zincs? My diver replaced my B-36.7 zincs while doing bottom scraping.

[boatpoker]

The critters have no effect on the galvanic cell created by your anodes, they are irrelevant to that part of your issue..

[deluxe68]

And you would need different zincs (material) for fresh water.

[boatpoker]

Originally Posted by deluxe68

And you would need different zincs (material) for fresh water.

think you mean "anodes".

[valhalla360]

Is this the stillete outdrive or a saildrive? If it's the outdrive, simply tilt it up out of the water. Amazingly the boat in front of me has one and it's about 1.5 ft in diameter with all the growth when all he had to do was tilt it up and it would be perfectly clean and no risk of corrosion.

Otherwise, in theory such a device should work. The problem is getting and keeping a good seal.

Even better would be to fill it with air:

A large bucket with the bottom cut out and a thick rubber seal that matches the hull bottom shape. Tie it off to the rails on either side to hold the bucket in place. Then use an aquarium pump to fill the bucket with air. With the top sealed to the hull bottom and air rising inside the bucket, the water should drain out the bottom as air displaces it. Aquarium pumps are designed to run 24/7, so as long as you have shore power, no problem...unless the drive is a particularly deep and the pump can't overcome the head.

You still have to get in the water to place it but a 3rd line at the bottom of the bucket should allow you to pull it out before departing without getting wet.

[Cotemar]

Why not just paint the prop and sail drives with sail drive paint.
They will need little to not cleaning and the zinks will last a good long time.

[valhalla360]

Originally Posted by Cotemar

Why not just paint the prop and sail drives with sail drive paint.
They will need little to not cleaning and the zinks will last a good long time.

Because if paint worked reliably, we wouldn't have thread after thread about bottom growth issues.

Another thought, the bucket over the drive by itself likely would help a lot with growth (salt or fresh water). Most of the stuff that grows on the bottom likes fresh oxygenated water. Cut off the access to more water and once the oxygen is used up, growth stops. What I'm not sure of is what the effect it will have on corrosion.

[YachtBroker]

We recommend any owner with a saildrive haul the boat to change zincs. We've have 3 instances in the last 2 years of divers changing saildrive zincs and for whatever reason they didn't get the adhesion needed and in all 3 instances the drives were literally shot, not worth saving, and had to be replaced.

We've also seen one saildrive that the boat (not one we sold) was not grounded properly after a generator install and the saildrive was so hot it ate holes in it in 6 months.

Remember the dock your on and your neighbors (and how well both are grounded) has as much to do with your zincs wasting away. I highly recommend galvanic isolators be installed for any stray current.

[bsurvey]

your suppose to have a galvanic isolator


yanmar has a service bulletin it will stop the zinc from wasting away and stop your sail drive from becoming a zinc

[DotDun]

Originally Posted by valhalla360

Because if paint worked reliably, we wouldn't have thread after thread about bottom growth issues.

Another thought, the bucket over the drive by itself likely would help a lot with growth (salt or fresh water). Most of the stuff that grows on the bottom likes fresh oxygenated water. Cut off the access to more water and once the oxygen is used up, growth stops. What I'm not sure of is what the effect it will have on corrosion.

Galvanic issues must be dealt with before paint will do anything.

The right paint works, the unreliable part coincides with the human factor, i.e, wrong paint, applied wrong or not at all, etc.

The paint keeps the barnacles from growing, slime/algae still collects on paint.

I've had very good luck with Trilux.

[fstbttms]

Originally Posted by YachtBroker

We recommend any owner with a saildrive haul the boat to change zincs. We've have 3 instances in the last 2 years of divers changing saildrive zincs and for whatever reason they didn't get the adhesion needed and in all 3 instances the drives were literally shot, not worth saving, and had to be replaced.

[grjfield]

Thanks for all the replies. Lots of great info.

I'm an ex diving instructor and had decided long ago against doing it underwater.... In my mind its hard enough to get it right..on the hard.

Saildrive has proper aluminum paint..i forget brand name at the moment.
Growth on bottom or saildrive is minor and as noted..not part of the zinc issue. The little creatures seem to like the flex o fold prop!

Its a saildrive (Sillette Sonic MK1 - electric). no tilting allowed unfortunately! I'm surprised how many owners in our marina keep even their little outboards with the lower legs in the water.


looks like I have lots more to research..
galvanic isolator,
neighbours with stray current,
large bucket with bottom cut out...hmmm...simpler! I thought going with a fresh water enclosure would have a zero pressure differential so the fresh water would stay enclosed...vs... needing a strong seal to hold an airtight seal..but its worth a test.
hadnt considered a different zinc for fresh water..this could kill the fresh water deal!

I'll report back.
Thanks again!

[belizesailor]

Galvanically the sail drive is already designed to be isolated from engine. If you are wasting zincs quickly then you/neighbor/marina have an electrical issue. This is why I dont like to stow in marinas long term.

When leaving mine in water long term (6 months). I remove the props (easy to do in water) and bag the sail drives with heavy duty trash bags. This eliminates at lot of growth.

[Thumbs Up]

volvo saildrives are isolated