Mynew old boat

Marine Max here in Miami just burned up my engine: idiots were playing with it, and then walked off and leaving it running, during service. Engine virtually melted and broke bigtime.
It is raining a mixed yuck of oil and water now, and has returned by trailer to my great auto garage, where just last week it checked out and perormed perfectly perfect in all respects. ArgggHHHH!
Trouble is, I love the jet boat part of the deal, it is a "new" boat to me, perfect for my needs, and engine was in great shape before the" service" (they were doing BODY work no mechanical!!)and I will not switch to out-board, so I guess I have to rebuild it. Or replace it.
Where do I start? Can I get new engine somewhere for this, my beloved 94"Boston Whaler Rage? I have a good old fashioned engine lovin' auto mechanic, who will do all he can to help me with this.

Is there a jet engine I can "susbstitute"? OMB is out of business ( Johnson and Johnson , right?) so parts must be frightful hard to find and cost big$, correct?

Any and all counsel( except "walk away and keep on walkin" will be appreciated. I already love this Whaler in particular.)
I am esp. wondering if there is a Yamaha that I can drop in, or some other jet engine, and what size is sugggested by you other Rage users?( I have heard the original 115OMB was an 'underpowered' choice in the originall install on Rage14'.

What size model etc. to get, and do the change out with, would be fabulous to know from someone who has done it that way.
If not, how do I begin a re-build? Any advice appreciated.
I am still a little sick as I write this. They just blew it up today this morning, and I will likely have to sue to get them to take any responsibility for it.