Re: Mercury 650 problems – is it worth an overhaul?

[mercuryspecialist]

Sneezing and hard to start are often indicators of the carburetor low-speed mixture being adjusted too lean. I like to use a pencil to draw a small line showing where the slotted (low-speed) mixture screw head is "set", and then carefully noting the amount of turn, turn (clockwise) the mixture screw until it "seats". For a 1975 model, often, the adjustment will be approximately one and one-half turns counter-clockwise open from seated. Both the top and bottom carburetors should be adjusted the same. If the mechanic did adjust carburetors to approximately one and one-half turns open, then adjusting both carburetors one-eighth of a turn counter-clockwise can be experimented with to try on the water for improvement. The specifications call for 4800 to 5300, and I would certainly want to achieve around 5300 to 5500 when lightly loaded. As a 1975 is a battery powered CDI ignition, and the ignition components are real money, I dislike reading that the wiring is "rough, but will last a season or two". Sounds like a sure way to blow/damage the switchbox (ignition module) and/or rectifier, and offer a (small) risk of an engine fire. My first thought on the reverse lock would be a missing, damaged, or incorrectly indexed reverse lock cam.