I've built this one a couple of times. Biggest engine I've had on them was a 70hp 2 cycle Mercury, but I think with modifications they would hold something bigger.
I just acquired a 1983 Starcraft HIN STRL06850783-A4
The HIN decoders I've seen online will decode the STRL06850783 part, but I haven't been able to learn anything about what the -A4 suffix means. Can someone here shed some light on this?
Thanks
This^^
Sometimes a serviceable used one turns up, but otherwise they go for big money.
https://www.dougrussell.com/catalog/product/view/_ignore_category/1/id/25862/s/hge-2-3l-exhaust-manifold-for-omc/
This stuff works better than anything else I've used and I've used all sorts of home made and commercial products. It's pricey and be careful not to get it on anything made of fabric, but it works.