Join Date: Apr 2006
Thanked 147 Times in 144 Posts
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Like Mitch says, oven cleaner is mainly for paint. It is lye, a strong alkali, and it will soften or stain the gelcoat if you don't thoroughly neutralize it (with a mild acid like vinegar) and then wash it off very thoroughly.
Whether it is paint or vinyl (to me a decal is a water-transfer slide that you put on plastic models) don't be surprised if it leaves a "shadow" because the gelcoat has worn around it, and there's now a white raised ghost of the old name after it is all removed.