Weeeeee...that is a beast of a boat. Fresh power and she should be solid from now on! Had buddy with same dilemma couple years back on his Hewes 18 LT....but he loved his....He re-built and thats almost exactly what it cost. It was OEM block but it let go few years later so he re-powered with new Yamaha F150 this summer and its a very different (and much faster 55+) boat yet still floats just as skinny.
I have a 96 hull and engine so my day is coming but my mindset when it does is not to hang used power. Yet...lol...I am going to have a 2 stroke Pro V to sell if she doesn't die first. Shooting for spring cause those 175 SHO's are hard to find now. They do have the extended warranty at no charge now too and thats what I am striving for. I was skeptical until I priced a new complete rig. Suddenly even Yamahas aren't so expensive ha. OR at least just buying an engine isn't compared to new sled....and since you have very little in it...you should be able to hang that SHO and sell it if you had to and re-coup.
Its not "just the powerhead" though on engine that age. New OEM lower unit is 2500.00, Tilt/trim is prob close to 1K and other parts that 20 years have taken their toll on...and that oil pumping....if you do re-power he parted out his blown engine for a couple of thousand I think though so even though she isn't running its still worth some coins in your pocket.