I have no idea without seeing a picture, but I'd assume it's the classic Fiat twin-cam motor. Heck, we don't even know what year the boat is to make an educated guess.
The Fiat twin-cam is actually a pretty technically advanced little motor for it's day. Aluminum, twin cam, cross-flow head, pent-roof chamber, single or dual webbers. They made them from the 60's to the 90's, in displacements from 1300 to 2000cc and stock power ratings from 90 to about 130 hp. High winding suckers - think 7000 rpm 40 years ago.
They are also highly modifiable motors. Sort of like the small block Chevy of the rest of the world. Cheap, small, light, so a good choice for tuners.
(of course it's not as good as the Alfa twin cam, but that goes without saying )
Don
'01 22 Classic, 502/B1
And a bunch of other stuff
"If everything seems under control, you're just not going fast enough" - Mario Andretti