I did a bit of reading about this set up and apparently the vapor seperating tank being water cooled (why it corroded) is to cool the fuel pump, without it the pump can overheat and fail prematurely.
The only other option is to convert back to a 4 bbl carb. That’s actually not a bad plan if you plan to keep the boat long term since all the parts are in the aftermarket.
If it’s a Ford 5.0 (distributor in front) you’d need a cast iron OMC/Volvo marine Ford 4 bbl intake manifold & a Holley 4160 4 bbl carb. You might be able to use the low pressure fuel pump from your EFI system if the pressure is not too high for a carb. Volvo & OMC both used this engine with the Holley 4 bbl before switching to EFI. Carbs are much easier to deal with with old boats because the parts (carbs, fuel pumps, etc) are all available in the aftermarket. Holley carbs are very easy to get parts for.
I would:
find a cast iron 4bbl manifold, I saw one on ebay today
buy a new Holley 4160 carb that is jetted for the 5.0 Ford (Holley sells them that way)
tale a look at the port side of the block, see if there is a block plate for the mechanical fuel pump. If so that's good news because you can use a Carter marine fuel pump and get away from those trouble prone electric pumps
get a length of Sierra marine fuel line
put it all together and be free of Volvo's lousy habit of making parts for older engines NLA.
I have a Rochester Quadrajet on my engine that I've rebuilt a few times, it also has a mechanical Carter fuel pump and I have a spare Holley 4bbl as well as another brand new fuel pump in the box. While the carb may not run as well consistently as an EFI or throttle body system for repair they are light years better. Parts are available, and not crazy expensive, except the price of Holley carbs new has gone up a lot.
intake manifold:
https://www.ebay.com/itm/203571045427?h ... R46-tpXRYQcarb:
https://www.holley.com/products/fuel_sy ... ts/0-80364pump:
https://www.summitracing.com/parts/crt-m60389pump fittings:
https://www.crowleymarine.com/omc/oem-p ... ump-filterwhile the fuel line may be NLA, these can be made up by a half way decent mechanic. just like brake lines.
Yeah it a lot of $$$ but adios to NLA nonsense, if it's any consolation Mercruiser does the same thing with making stuff NLA.