Checking Bias circuit

[Paul]

I would like to check my bias circuit in my 2.4 BP. The merc manuel says if equipped with an idle speed stabilizer/ or high speed spark advance, disconnect and isolate both leads from switch box and repeat check to rule out possible/spark advance malfunction. I do not have a idle stabilizer I believe but how do I know if I have a high speed spark advance and what color wire would that be?
Thanks Paul

[j_martin]

The screws on the switchboxes that are jumpered together are the bias terminals. Anything besides that jumper between the switchboxes on those terminals goes to a timing module, ie idle stabilizer, advance module, etc.

It is the upper left stud on the boxes, and the normal wire color to it is white with a black tracer.

hope it helps
John

[Paul]

I will check that out.

Thanks

[pyro]

There shouldn't be any advance box or stabilizer on this motor, just mechanical timing. :confused:

What's the motor doing wrong?

[Eagle One]

To check the bias circuit on each switch box disconnect the wire connecting the two boxes and using an OHM meter place the positive probe on the top left lug and the ground probe on the side of the box you are checking. A high performance box will read 9,000 ohms and stock production box will read 14,000 ohmxs. If they vary over 200 - 250ohms you need a new box.

[Paul]

After checking the bias circuit I come up with 09.70k ohms on the outer box and 09.60k ohms on the inner box. So I'm looking at 9700 ohms and 9600 ohms correct? If so I have 2 bad boxes and what would be a good box to replace my bad ones with merc or aftermarket and who has a good price? My current box's have a part no. 332-7778 A2 and May 1987. Thanks for all the help.

[GamblerSS]

Hey Paul,

I see your from Wausau.

I just picked up a couple switchboxes a few weeks ago for my Bridgeport EFI to replace my original ones from '87 also. The new superceeded number ended in A15. They were the OEM Mercury HP ones and I purchased them from Rib Mtn Marine.

If you ever run on Lake Wausau, maybe I'll run into you sometime.

Gambler SS

[Paul]

Did they have them in stock or did they order them for you, and if you don't mind me asking how much did they charge? It has been a couple of years since I have been in their store. Another guy in Wausau that can help you with parts is Steve Kell at M&J sports, he has helped me out alot in getting parts for my BP. Steve is the service manager.

[GamblerSS]

Paul,

They had to be ordered from Fond du Lac but were in stock at Mercury. They were a bit cheaper than another dealer I had checked with... I don't remember the exact price though.



What is your motor doing?

[GamblerSS]

Hey Paul,

I forgot to mention....If you call them, ask for John. He's the owner.