Saildrive query

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Slowtack

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Ready to put saildrive (Volvo 120SB) back together. Great condition overall but I am a bit concerned about some corrosion pitting around the circumference on the top surface where it will be pressing up against the rubber diaphragm. The depth of pitting is very minor but it is fairly widespread and could affect the quality of the seal. Options that occur are to lightly skim the surface but that could affect the overall assembly length. A paint, resin or other or hard filler could result in a loose and friable surface and create a capillary path. I am tempted to smear on a very light layer of sikaflex but not sure what the downside of that might be. Any body got any better ideas?
 
The surface i am referring to is on the top of the intermediate plate between the lower leg and the rubber diaphragm.
 
Re: Sail drive query

We did this a few weeks back, gave the area a wire brushing then applied some rust converter; applied marine grease just prior to assembly.

Hope this helps.

Avagoodweekend......
 
Re: Sail drive query

Must be a different job you are describing Saltoz- wire brushing and rust convertor on aluminium??
Still, thanks for first reply after 176 views !!
 
Re: Sail drive query

Two thoughts:

1. Sikaflex is likely to make dismantling harder when you do it the next time (seven years hence /forums/images/graemlins/smile.gif). Not impossible, just harder.

2. Corrosion here suggests that there is a problem with the anodic protection. Is the anode in good electrical contact with the leg? If you use it for more than one year (I get 2 / 3 years out of mine) do you clean up the exposed surface?

I hesitate to suggest what would be best for filling the pits, but if it was me I think I might fully scrape / wire brush them out, then use etching primer to stabilise things. For actual filler there's a number of choices, but epoxy with micro balloons might be good, sanded flat.
 
Re: Sail drive query

Thanks DaveS. No corrosion elsewhere inside or out, the unit is in very good condition. Maybe the pitting is due to salt ingress when the rubber compresses over time reducing the seal quality. Wil think about the epoxy but the pitting is so shallow there may not be enough mechanical key for such a thin brittle overlay.
 
Re: Sail drive query

Hi Slowtack!I think I would not worry too much about the pitting, clean it up as you suggest and etch prime and paint with primer and topcoat. (ask Volvo agent for recommendations). this will then not affect the clearances adversly.the diaphragm rubber will compress into any small pits and will surely seal ok?
I sympathise with you on this one as it is a big job to undertake (leg)and one does not want to have to repeat any steps, esp after launching!
 
When I replaced my 120S saildrive diaphragm some years ago, I asked the Volvo agent if he had ever heard of any of these fail. The only failure he'd heard about was when an owner lubricated a new diaphragm to assist assembly and it somehow slipped out of the clamping ring.

Otherwise, I can't help with your corrosion query - sorry.
 
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