I've smeered Permatex Ultra Black RTV on mounts before with good results.
https://www.permatex.com/products/gasketing/ultra-series-gasket-makers/permatex-ultra-black-maximum-oil-resistance-rtv-silicone-gasket-maker-4/
But it's tough to get down in the base crack.
I also used the as seen on TV Flex Seal spray on CV axle joint boots to protect them.
https://www.flexsealproducts.com/product/flex-seal/
Seems to be holding up well on the boots. Perhaps it might work on the motor mounts too.
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