THis is the basic issue:
First, are you maintaining this old boat as a traditional Chris Craft?? Or
do you just want some reliable engines to go boating with??
There are lots of possibilities. Right now I'm enamored of VW diesels,
and a couple of the later 100 HP types would be 'nice'. Anything like
this will be expensive. Take a look at: www.lancingmarine.com for some
interesting ideas.

I have an idea for a low-cost conversion using modern transverse-mounted
car engines including their transaxles, but I have no proof of the
concept. I have heard references to this being done in the 3rd world.

In the 50's I had a cruise on a Prince Edward Island lobster boat that
ran a Buick straight 8 with dynaflow transmission right from the
junkyard, open engine, tractor-type exhaust. The fisherman said "I can
get another engine for $25 any time..." He had to rev it a bit in
reverse.. but..

--
Regards, Terry King ...In The Woods In Vermont

The one who Dies With The Most Parts LOSES!! What do you need?