i just bought a mercury 850 and upon inspection after bringing it home i found a box on the front of the motor i believe its called a switch box with wires comming in from key switch and going out to dist. just wondering if there is anyway to bypass this thing i would like to know if motor runs before putting 320 dollars into this thing.
Have you tried the motor to see if it runs with the switch box the way it is? If not, give that a try first. You might be pleasantly surprised.
If a switchbox is faulty, you might find that half of the cylinders work while the other half do not. Stator or coil problems could cause the same or similar symptoms. A process of elimination is then needed to determine the source of the problem. The procedure is somewhat complicated, but a search of this forum and/or a service manual should tell you what to do.
Mike, There is a switchbox test in the FAQ of this forum. You might test it. You might also test the distributor. Both are pricey. Take a compression test and inspect the LU gear oil. If those are good, the rest is easy.
yeah,their not cheap...i think the dist housing is 360.00.and i believe if ya scout around you should be able to do better on the price of the box...good luck.
Mike, Distributor ignition Mercs do not need a stator to run. They run on battery power. The stator and rectifier only charge the battery. After you fix your wiring harness, you might crank her up on the flusher and see how she runs.
Mike, There is a switchbox test in the FAQ of this forum. You might test it. You might also test the distributor. Both are pricey. Take a compression test and inspect the LU gear oil. If those are good, the rest is easy.
I would to see that listing in the FAQ forum could direct me to it? Im having a problem also with my switch box, I have a 78 mercury OB 402 2 cylinder with no spark and had it running before... Thx
Merc switchboxes are nothing but trouble, based on my experience. They fail for no apparent reason and cost a fortune to replace. Not one of Mercs better ideas, IMO. I could use one for my otherwise good '78 400, but may just junk the motor instead of spending the money.
ok sry about all this but im new to boat engines worked on just anout all other things even f-15 and b-52s but can someone please explane to me what the switch box does besides send power to the dist. also i havent looked but from what i understand the dist. also has points is this correct? sry but im a newb and learning
Mike, that's a good question. At least for my Merc 400, I thought that the switch box acted like a distributor and sent the spark to the different cylinders. I did not know that it also has a "distributor" in the automotive sense of the word. Does it or does it not?
Mike, On a distributor-based ignition like your 850, the switchbox stores battery voltage, converts it to a higher voltage (12V becomes 300V), and dumps it into the ign coil, upon command of the trigger. The trigger on your merc is a hall-effect trigger.
On motors w/o a distributor, the switchboxes have the same function, however, they have multiple outputs which go to seperate ign coils, one for each cylinder. Upon command of the trigger under the flywheel, they dump voltage into the correct ign coil for the cylinder that is in position to fire.
ok so theoredicaly you could just get a coil that puts out the same voltage as the coil after the switchbox sends it (300 volts) power and do without the switchbox ( not that i would do this) its basically a preamp for the coil which is the amp ( power gets bumped up twice) is this correct? just trying to understand ( knowledge is power)
mercury switch box?
Linear Mode
