1966 vs 1967 Mercury 650 Wiring Harnesses

[mbrownone]

Im thinking about purchasing a backup motor for my boat. Currently I have a 1967 Merc 650 (65hp 4cyl) that needs some tweaking. Found the same motor, only it is a 1966 model year. Not sure what the differences would be between them. I would appreciate all the comments/sugggestions/advice...thank you

Will the '67 match up with my existing wiring harness and controls???

Possible differences:
1. fuel/oil mix (50:1 vs 40:1)
2. external wiring harness (will each motor hook up correctly on the same harness)

[jerryjerry05]

Harness should be the same.
Oil at 40-1 ???? Is that what the manual says?
Most older motors need a 50-1.
Some smaller want 100-1 most 50-1.J

[Laddies]

In 1966 the 650 came with a magneto but in 67 some were magneto and some were battery powered CD so there are 2 types of ign harnesses, other than the ignition systems they were the same engine.

Both were 50 to 1 engines, Mercury never recommended 100 to 1

[mbrownone]

Seems to me that I read recommendations of different fuel mix ratios for pre-1966 engines, but wasnt really certain. I agree 50:1 should be sufficient though. Im going to buy the motor to have another clean motor with spare mechanical parts. These are great engines!

Thanks again. Once again this forum is a great resource! Spring is coming...

[emckelvy]

50:1 is fine, 40:1 gives the old bearings a bit more lube. Neither will hurt these motors although if you're running a richer oil mix it's not a bad idea to run a dose of Seafoam or other carbon cleaner additive on occasion.

Your 1967 Merc external control harness will plug right into the '66 motor. The type of ign doesn't matter, as there are extra pins in the external harness, which cover more than one type of ignition function.

The difference lies in the motor-side plug, which will only have the pins needed to operate its style of electrical systems.

HTH & be sure to snap up that '66 classic "650" before it's gone!............ed

[Laddies]

The harness will plug in but the switch is not interchangeable so the harness will not work. That's why Mercury lists 2 different harnesses one for a magneto and one for battery powered CD. It was also Mercury Marine that said you can run any black Mercury Outboard 50 to 1 in a late 60s service bulletin.