First time pontoon boat owner needs a new motor

[Woodland Artisan]

Just bought an old '95 Suntracker 21' Fishing Barge pontoon boat knowing that the motor with it was likely bad.  It's a Mercury Tracker 40hp Pro Series and I'm assuming it is the original motor.  It turns over and the tilt/trim works but the seller said that the pistons are scarred and I see that some things are missing in there from where someone was trying to fix it.  Will get it looked at by professional in the next few weeks to see if it's even worth saving.  I know nothing about motors.

With that said, I'm asking for recommendations for repowering this boat. It's use is just going to be puttering around fishing and (slowly) cruising with just a couple of people at most once in awhile.  No towing, no watersports, no blazing around the lakes, obviously.  The max hp on the boat (when new) was 90 hp but I'm looking anywhere from 40 to 70, I believe?

The boat is in good condition and was made even more of a fishing boat with a small center console and all but a couple of fishing chairs removed.  If I can figure out if this can be repowered (or motor repaired) reasonably, then I'll start on a wholesale refurbishment.  But, still maintaining that minimal fishing boat or kayak/exploration mothership usage.

[rps]

message fishinwrench. I bet he has or can get you a used, refurbished Evinrude.

[fishinwrench]

I have one going into the oven very soon.  

Should be ready by mid-September.  

4600.00 with controls and a 2 year full warranty.  

Installation/rigging on a toon = +350.00 (may work a trade for what is currently on there).

[Woodland Artisan]

Is going the max hp rating for an older boat likely to be a problem?  Honestly asking.  I have no idea if it's something I should be concerned about especially since I'm not going to be zipping around the lake anyway.

I've attached some pictures of what it has on there right now.  Took the hood off and this is what I found.  Pretty sure there are some bits and pieces missing in there somewhere. <grin>

[fishinwrench]

1 hour ago, Woodland Artisan said:

Is going the max hp rating for an older boat likely to be a problem?  Honestly asking.  I have no idea if it's something I should be concerned about especially since I'm not going to be zipping around the lake anyway.

No, and it will actually improve the resale value of the boat more than enough to compensate the cost difference between it and a smaller motor, when you decide to sell it.  

Making a boat more versatile always improves it's value because it appeals to more people.   You don't have to run it wide open if you don't want to, but having the capability to tow tubes and skiers, or the ability to outrun a storm, is never a bad thing.

[fishinwrench]

That 40 is toast.  Looks like it overheated and threw #3 out the side.  

She's scrap metal.