Sand blasting engine parts

[p.hammar]

Hi everyone. Some time ago I posted questions about my engine renovation and particularly about sand blasting engine parts. It's going well and I am blasting away at all parts that are not related to sensitive systems, like fuel.
Now I have come to the gearbox, which is severly corroded after having been submerged in salt water. Se picture. I can take it off from the bell housing that it is attached to now, but then what? Putting it in the blaster cabinet seems stupid, as there are bearings between the gearbox and the shaft coupling that comes out of it, and I cant protect that from flying sand. What method would you use to clear this from all the horrible white and grey stuff?

[Lepke]

A durable tape and care when blasting.
There are chemicals you and soak or brush on that remove corrosion but leave good metal. Be careful with aluminum.

[Bellinghamster]

You should be able to take off the bellhousing adapter and engine mounts and sand blast those seperately. Tape up the input and output shafts making sure to cover the seals fully, also cover the shift lever and vent (if there is one) and blast away. Alternative is a wire brush and wire wheel in a drill or angle grinder, but you should still tape off the shafts if you go that route. A small wire brush (the size of a toothbrush) will also help get behind the coupling and into tight spaces. They're available at most hardware stores and welding supply shops.
Prime bare aluminum immediately after blasting/wirewheeling with this https://www.go2marine.com/Moeller-7-...osphate-Primer (or equivalent zinc-rich primer), or epoxy primer (https://www.go2marine.com/InterProtect-2000E-Kits) before painting.

[7th wave]

Any engine or gearbox components, after the blasting with abrasives will have reduced the longevity as embedded particles will be liberated into lubricant and continue its job of being abrasive. One can not rely on filters to deal with such element.
Better option is "hot tank" at any engine rebuid shop, and if required followed by brass wire brushinng, CO2 or soda blasting, post high water pressure wash is mandatory, followed by complete compressed air drying. Costs are nominal. Aluminum requires specific bath.
Soda blasting also reduces the corrosion under the certain circumstances.
If you want to go really fancy, use dedicated coating inside the oil galleries (OG) to reduce oil and solids adhesion to the OG, improving lubrication system qualities. This coating also entraps any loose particles to be.
NEVER sandblast any reciprocating or rotating parts located within OGs!
Also, nice clean clean finish after the sandblasting might become a nightmare over the time.
Best of luck

[Bellinghamster]

After sleeping on it I'm going to amend my advise: if it has been submerged, you probably want to disassemble and clean and inspect internal parts, especially input and output shafts, seals and bearings as they may be compromised (corroded) leading to a short life of the gearbox. If it didn't get any water inside, it still will suffer from corrosion of the input and output and shift shafts, and likely all external fasteners will eventually seize.

[SailingHarmonie]

That looks like a small ZF tranny. They can be a nightmare to disassemble and repair, even when in perfect condition. Seriously consider just replacing it.

If this has been submerged, I would never trust it out of sight of land ever again. On second thought looking at that one, I'd not trust it out of sight of my home marina.

[Lou-In-NJ]

Originally Posted by SailingHarmonie

That looks like a small ZF tranny. They can be a nightmare to disassemble and repair, even when in perfect condition. Seriously consider just replacing it.

If this has been submerged, I would never trust it out of sight of land ever again. On second thought looking at that one, I'd not trust it out of sight of my home marina.

I totally agree with SailingHarmonie..that corrosion isn't likely just skin-deep.
Good luck...please post pictures when you're done if you proceed.

[p.hammar]

Well, it sounds like I need to open it up and assess the damage. It hasn't been fully submerged, but has stood in brackish water to about one third of its body. The oil coming out of the vent as I turn it upside down has a good colour and it ran very smoothly when I tested the engine. But opening up seems inevitable then... SailingHarmonie, what is a ZF Tranny? This one is a Volvo Penta MS 10L. Strangely there is no YT-video of anyone taking one apart. They are quite common... I think I can take the risk of taking it apart as long as springs and cogwheels don't come flying all over me. Will not sand blast but rely on steel brushes and being careful. I see no need for painting it after cleaning, as I hear it makes no difference to it's life span. Opinions are, as always, wellcome.