4:23 foil tape for joints. Sheets have self-adhesive backing or use screws and large washers. This is a marine product.

I'm surprised I supposedly established company has not replied to you. He does say the transom exit is dry so to answer your question I imagine no there is no tail tail sign of water which is a bit worrying

@@iman80skid91 I was surpised and disappointed as well. This company has probably been taken over or whoever was dealing with KZbin left, so this isn't monitored. I think I'd just add a small tell-tale into the raw water circuit just ahead of the anti-syphon loop. Probably exiting high on the topsides where it can be seen from the centre-cockpit helm. The raw water pumps more than twice what the engine needs for cooling, so a bit for the shaft seal lube, a bit for a tell-tale and the rest for the exhaust will work. I wish generally that companies that sell heavily-priced marine stuff would actually provide more useful info and tell us stuff like this so we don't have to work it out ourselves...