I bought a 1970 Evinrude 6hp outboard to power my Sunbird to and from the ramp, and for when there is no wind. I chose this motor because the price was right: A few hundred $$ vs. $1,000- $1,400 for a new one. Also, it was in very good condition. In addition, it weighs only 43 pounds, while newer ones I looked at were from 53 to 85 pounds. The weight advantage comes not from flimsy construction - in fact the Evinrude is impressively built - but from the fact that it is a simple 2 stroke design, unlike the modern 4 strokes. The Evinrude is not as clean burning as newer designs, but this is a motor that will see maybe 10 hours use a season. In addition, the motor needs to be removed for trailering. The far more expensive, and far heavier newer motors simply do not make sense for me, even if they are cleaner burning. The Evinrude has other advantages, too. As a 2 cylinder 2 stroke, it has 2 power pulses for each crankshaft revolution, vs. only 1 power pulse for 2 revolutions in a single cylinder 4 stroke. It produces it's rated power at lower RPM's than the 4 strokes, and is very smooth at all speeds.
It is a good idea to check the water pump on these motors, and I found my impeller to be worn out, and the pump housing corroded. Impellers are cheap enough, but housings are not. I decided to save some money and bore my housing out, using my Harbor Freight Mini Mill. I made a stainless steel liner from my scrapped Craftsman air compressor. By lucky coincidence, their inside diameters were the same. At right is a picture of the bored out housing and new liner.
One other problem I had with this engine was a very stiff throttle. I traced this to the bottom bearing of the vertical throttle shaft. Here they used a nylon bushing which had very close clearances to both the engine frame and the bevel gear. Some aluminum corrosion built up between the bushing and frame, nearly seizing it completely. It took a lot of effort to wiggle it free. Once clear of corrosion, I lubricated it with silicon grease, and it operates smoothly once again.
Here is the vertical shaft. The stainless clip goes on the top end, and the nylon link connects it to the bevel gear. The bevel gear on the horizontal shaft is shown below right, and the shaft is below left. The shaft is solid brass, and is in much better condition that it appears. The bevel gear is aluminum, and also in great shape. The screw pinches it to the shaft, but even if it is loose, it will not turn because both the gear and shaft have a flat side
The next thing I looked at was the tilt mechanism. Initially very stiff, it soon loosened to the point where the motor would fall back down. I disassembled it to see how it worked. It uses a plastic cone for friction and a very thick spring to put compressive force on the cone.
Not shown in this picture is a flat fiberglass washer that is on the spring side of the tilt mechanism. It is a thrust washer that prevents the aluminum pieces from rubbing against each other. The spring and bolt were originally aluminized. I treated the rusted areas with rust converter, and then painted them. I put silicon grease on the plastic cone when I reassembled it.
Taking the flywheel off proved to be a challenge. Like nearly everything else on this motor, it appeared to be undisturbed for the last 42 years. I bolted on my Harbor Freight puller, and it did not budge, even though the 1/4-20 stainless bolts I screwed into the flywheel were bending under the load. I tried a few gentle taps, and nothing. I heated the flywheel, still nothing. Finally, I supported the flywheel with 2 metal bars supported by sawhorses. Now I could safely whack the top of the puller without worrying about shock loads on the crank and bearings. That worked. and I didn't have to hit it very hard.
Removing the flywheel exposed an ignition system in pristine condition. Everything looked original. I replaced the condensers, but being cheap, I filed the points. They are working well, and may last many hours.
The points are set at 0.020", and care should be taken to be precise, for the point gap affects the ignition timing. Even better, use a timing light. If the Set Points mark is between the two marks on the engine, it is correct. Time the top plug with the Set Points T and the bottom with the Set Points B. 1,000 RPM is recommended, but is not critical as the timing does not advance with RPM relative to the timing marks.