Well.....I am no expert but it sounds like you might have a 1959 Crosby Capri and I believe a Mercury/Super Thunderbolt Mark 58A outboard motor. It is possible that that was the original motor purchased with the boat.
I am stepping away from the keyboard now. I think I will have an adult beverage!
Post some pictures of your boat and motor please. I always liked the Crosby's. Years ago I remember reading an article in the Antique Outboarder about an endurance run they did with a Crosby that had 2 Mark 58's on it and they ran it up the Mississippi River.
The 58A was the 1959 model of the Super Thunderbolt so it is possible.
Any chance of you posting larger pictures??
I have attached a picture of a set of twin 400 Mercs I restored last year for the fellow driving the PowerCat.
I also have a 59 Capri Delux Custom just like yours, mine came with a 59 Mark 55AE & Ive seen originals with Evinrudes as well, so it was up to the dealer what motors came with them, Im thinking.
gotta love the dashboard in these rare boats eh, a copy of 56-57 Corvette dash
I am going to put a Merc 1000 on mine this spring, I need a bit more power for high speed tubing & I have a 36ft parasail to try to pull this summer
Does your Crosby have the Capri Emblem on the dashboard? mines missing & im looking for one or another possibility is to get a plaster of paris mould made from one
do you have any upholstery if so any possibility of a pic of your seats
I read a few old articles about these boats and in its time it was considered the fastest hull & apparently the astronaut Allan Sheppard raced one in APBA