When I bought my E38-200 the coaming box was already replaced with a store bought plastic coaming box. It was a shoddy job and needed to be replaced. I made a custom fitted wood box and fitted it into the existing coaming opening. It took some careful measurement, templating, some additional screws and generous caulk, but it turned out great and has held up now for several years. Here is a photo. The two holes below are drain holes to eliminate water accumulating in the box.
Dave
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