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

[mercuryspecialist]

[/quote]Thanks for your input. I mentioned that I was planning on rewiring it over the winter. He said that I had to use the exact same gauge and length of wire had to be identical as the wiring in this system is resistance sensitive.

As for the tach, a sticker under the hood said to make sure the tach was “quicksilver compatible”. Truth or fiction?

Also,I was told the top and bottom carb are different sizes because one carb feeds one cyl and the larger one feeds 2 cylinders. This is the strangest thing I have ever heard.

Lastly, do you know where I might find replacement harnesses or someone who makes them?[/quote]

Although I would recommend the same gauge, color insulation, and length also, the system is not "resistance sensitive".
Yes, the tachometer would need to be Quicksilver compatible, if connecting to the ignition system. However, if instead connected to the battery charging system, then a modern alternator driven tachometer such as a Teleflex can be employed. Note that the engine wiring harness’ s tachometer brown wire must be then moved to connect to one of the AC side rectifier terminals to receive a signal from the charging system instead of the ignition system.
The carburetors are not different in size. The top feeds the top cylinder, the bottom feeds the bottom cylinder, and both carburetors feed the middle cylinder.
CDI does state to offer to rebuild your original. In the past when I have spoke about having a harness rebuilt, it was said to be six or more weeks to do so. They do show a new replacement for the 1980 to 1990 models. This harness seemingly could be employed on 1976-1979 models also, but would require the matching plug type remote control harness as well. 1972 to 1975 models have instead a battery powered CD ignition, so the wiring differs somewhat.

Regards,
Joe
info@fergusonpoolemarine.com