That sounds great, and if you can get the engine's sorted at reasonable cost you could end up with a good boat.
I think next step is to get a really good assessment of what's wrong with the engines. Are both known to not work? Was there some event that led to that? I think you said they bar over? How does the oil look? Coolant? Fuel filters, especially any water in them? What's behind the whole "they sat too long is seawater" diagnosis? Did they physically sit in a pool of water, and if so, from where? Does other evidence support his, like a rusted pool water line? Or was there water in the fuel such that the insides of the pump were exposed to water? And if so, are there other signs of water in the fuel? It must have gotten in there somehow.
It's very possible that there is a ton more info that led to a correct conclusion by the mechanic. But from what we have heard so far, the diagnosis is not very credible. I'd even say highly suspect. And in a world where many techs just want a quick diagnosis (aka guess), change a part, and move on to the next job, thorough troubleshooting is an early casualty in the process, and you pay the price.
At this point I think you need to figure out two things with the engines. First is whether there really an a issue with the injection pumps, why both of them at the same time, what caused it, and how to prevent to again. It's quite a coincident if both pumps on both engines failed the same way at the same time, so that needs explaining. It's possible if there was a major water-in-fuel event, but there should be lots of other supporting evidence In other words, are the injection pumps really bad, and why?
Second, what else is wrong or weak on the engines? You want to have as full and accurate a scope of work to bring the engines back into service. Peel the onion now through diagnostics, not through a sequence of expensive repairs. A lazy tech will replace the injection pump, fire up the engine (hopefully), then see what repair is required next. With that approach you will know what you are getting yourself into only AFTER you are all the way into it. Fine for the tech, bad for you. Before you set out to fix anything expensive like injection pumps, confirm that there is no oil contamination, coolant contamination, check turbos for water ingestion or other issues, check compression, check value clearances for heavy wear indication, check fuel system for water or other contamination. Pressure test cooling system and raw water system (heat exchangers and aftercoolers can be VERY expensive to replace). I'm sure there is a ton more.
