Mid 70's Mercury switch box - 4cyl to 6 cyl

[Mercerman]

Will a switch box/power pack from a mid 70's 85 hp (850) 4 cyl work on a 76 150 hp (1500) inline 6. Sierra and CDI have the same part number for all 4 and 6 cyl motors from that era, but I can't find any info on the OEM part interchangeability.

 

[ajgraz]

Re: Mid 70's Mercury switch box - 4cyl to 6 cyl

Impossible. The 4cyl will be one switchbox for all four cyl, the 6cyl will be two switchboxes, 3cyl each (Note: 3cyl's use the same as 6cyl, only they just need one).

 

[Mercerman]

Re: Mid 70's Mercury switch box - 4cyl to 6 cyl

No - the mid 70's inlines used a single box p/n 332-2986 as did the 4 cyls. It wasn't till later when they started using double swith boxes on the sixes

 

[emckelvy]

Re: Mid 70's Mercury switch box - 4cyl to 6 cyl

Not true, the switchbox from a 4-cyl CDI (Distributor-Fired) system will run a 6-cyl CDI and vice-versa.

However, the tach output on the box will not function correctly (if you're using it to drive an original Quicksilver tach).

This is no big deal anyway, since 'modern' tachs are driven off of pulses from the alternator.

If your tach connection (brown wire if I recall or maybe grey, check the wiring diagram for sure) hooks to the switchbox, you'd want to move the wire to one of the yellow stator wires at the rectifier. And of course have the correct tach being driven by the 12-pole alternator.

HTH........ed

 

[ajgraz]

Re: Mid 70's Mercury switch box - 4cyl to 6 cyl

Learn something new every day!

 

[Mercerman]

Re: Mid 70's Mercury switch box - 4cyl to 6 cyl

Let me re-phrase.

Sierra Part # 18-5779
Replaces OEM part #

MERCURY MARINE 332-2986A27
MERCURY MARINE 332-2986A25
MERCURY MARINE 332-2986A22
MERCURY MARINE 332-2986A21

What I need to know is: Are all 4 of the OEM Mercury parts listed above interchangeable?

 

[Mercerman]

Re: Mid 70's Mercury switch box - 4cyl to 6 cyl

Thanks - My question was answered before I got my last reply in.

The CDI units dont even have a tach post.

That answers why they have the same part number but have different stickers on them stating either 4 cyl. and 6 cyl.

 

[verado7]

Re: Mid 70's Mercury switch box - 4cyl to 6 cyl

im just gonna say this for fun - NO!