Re: 1973 chrysler outboard 90 hp
The 90 is a nice 3 cylinder engine with Motorola Magna-Power ignition. This particular ignition is relatively trouble-free but the CD box does occasionally go bad. If it is running, compression ratio is good and it has good spark, it probably will serve you well for at least a couple of seasons.
It has a 2 piece lower unit with a splined shaft (18 splines), thrust pin drive. Props for this lower unit are becoming more difficult to find and usually you need to buy a used one on the auctions.
All in all, while the engine is good and easy to work on, it still is very old school. Unless the owner is giving you a really good deal, it is simply not worth paying too much for it. If I were selling the engine alone as a repower, I would ask 300 bucks and think myself lucky to get it.
Here is what I do with old Chryslers. However, I have gotten away from the 2 piece lower units in favor of the one piece (after 1979) simply because the one piece is better designed and there are many more props that it can use.