[Bushwacker]

If you have a wife, she'll like having the cabin and head on the Seafari, but she WON'T like being stranded with motor problems, so you're right to focus on reliability!

There are some differences on the older motors besides the ignition system Fr. Frank mentioned, which I agree is probably better on the Merc. The I-6 Merc is a mono block, i.e., the block and head are all one casting, which eliminates lots of bolts and the head gasket which can leak. However an outboard cylinder head is very simple and it's nice to be able to remove it to inspect condition of pistons and cylinders, although you can do that on the I-6 Merc with a borescope. The other difference I noticed is that the Merc's had higher performance powerheads (more hp/cu in.) and were built more like aircraft engines. They were typically a little lighter, using aluminum cowlings which were light but transmitted more noise than the F/G cowlings on the OMC's. Merc props are retained with a fancy tab washer to lock the nut; OMC's use a simple cotter pin like on boat trailer wheel bearing. Prop fit on the old OMC's was pretty sloppy, but the prop would slide aft every time you hit reverse, so less likely to become seized on the shaft. They used mostly fine thread bolts where the OMC's used course thread bolts. The fine thread bolts are stronger, but they also offer more surface area to seize up, which is a common problem on outboards due to galvanic action between the aluminum castings and steel bolts. (One of the main tools for working on old motors is the propane or acetylene wrench!) Not a problem if you stay on top of maintenance by greasing frequently removed stuff like water pump bolts, prop & driveshaft splines, etc., but when buying an older motor, was that done on it? Not trying to scare you off on buying an old motor, but just need to be sure you're getting into it with your eyes wide open!

Two friends of mine with Merc's paid big $ because they hadn't stayed on top of the maintenance. One had to destroy his prop to get it off because he hadn't greased the shaft often enough. The other took his to the dealer for a routine water pump change, expecting to pay a couple hundred $. It cost him over $800 (in 1975 $) because the driveshaft splines were seized inside the crankshaft! They cut a hole in the exhaust housing to cut the drive shaft and then had to completely tear down the whole motor to replace the crankshaft, driveshaft and exhaust housing! With the current $100/hr labor rates, these days a new motor would have probably been cheaper! When I bought my Seafari in 1975, the only real choice in motors were Mercury or OMC (Johnson & Evinrude, which are identical except for paint and decals), although Chrysler also made some very simple lightweight motors. Yamaha's came later and I have no experience with them, although I hear they're good motors too; imported though, so parts may be more expensive. At that time there were lots of 20-25 year old OMC's running around, and that's ALL you saw in the Bahamas, but you didn't see very many OLD Merc's. The Merc's had a reputation of being great fresh water motors, but they seemed to have more corrosion problems than the OMC's. Bought a new 115 Evinrude in 1975 and ran it till repowering/adding bracket in 2006. It still had good compression and was running good when I sold it, although it was getting hard to start when cold; I suspect the reed valves may have needed replacing. I picked the 115 instead of the more highly tuned 135 (with the same 100 cu. inch power head) because of better idle quality and long term durability. Although I had to replace numerous coils and one power pack and a starter, it never left me stranded once in 31 years and over 900 hours, so I had no complaints.