[bigeasy1]

I have a 1974 Tsunami with a 350 Mercruiser and an Alpha out drive.As mentioned Tsunami/Sceptre are the same thing.I love this boat and the way it handles.
The Bravo Drive is a heavy duty drive and is usually used in applications over 300 horsepower.
I wouldn't worry about a 15 year old drive unless it looks like it was neglected.My Alpha drive is over 20 years old and it works very well.
You do have to take care of them properly however if you want longevity.Is it a fresh or raw water cooled system?
If you're boating in the salt then a fresh water cooled system is the way to go.It keeps the corrosive effect of salt from taking a toll on the engines internal passages.
I would check it over very carefully,starting with the exhaust manifolds and risers look for any signs of rust stains leading away from the gasket surfaces.
I assume that you'll be able to run it,so check out the shift and throttle functions,both should be very smooth.The Bravos use cone clutches which shift vey nicely.

Things that need regular inspection and replacement on an I/O drive are
*bellows
*exhaust manifolds and risers
*gimball bearings
*u-joints.
*shift cables

Maintenace on a saltwater used outdrive is extremely important,if you see any areas that seem suspicious,you may want to have a marine mechanic check it out.I picked up a used Alpha Drive that had been used in saltwater,and it looked perfect on the outside,but when we tore it apart to install new parts,we found water jackets that had been completely rotted through.
I ended up buying another unit.

For me,I prefer an outdrive over outboards,as I boat only fresh water(Great Lakes)I like the big high transom,nice in a following sea,and easy to net fish over,and lots of area to mount downriggers and rod holders.

The regular stuff applies to the boat as you already know like rotted transoms.hatches,decks,corroded electricals etc.

As for towing I tow mine occassionally in the fall 400 miles one way to home and back another 400 miles in the spring.I pull it with my Ford F150 with the 5.4 engine.IT tows it fine,but I wouldn't do it without good working brakes on the trailer.

If it checks out good,you won't be sorry,they are an awesome boat and also a pretty dry ride in the slop.Good Luck.