Page last updated July 17, 2008



Mercury Distributor / Trigger

Common tools neededAfter running the engine for a month, I started to notice the engines fuel economy to be non-existant. I was getting bored with fishing so I figured I would continue with the restoration of the engine.
I noticed that the distributor was coated with a heavy grease; I thought this a sign that something was not right.


I remember reading in the manual to check this area so now, I will attempt to repair this particular part.
BEWARE - these parts are expensive. If you break something, it will cost you, so be careful and take your time.

After taking it apart, I am happy I did. I found the trigger to be in bad condition. The outer coil was cracked and there was a piece of wire sticking out of the assembly. Also, the rotor disc (the window like piece) was warped. I don't think the warp mattered much, but it did tend to contact the housing at different parts as it turned around the shaft.
I priced the part around, hoping I could find replacement parts to rebuild the trigger, but found that it was a one piece kit.

The part number for my Engine is: R332-4797, 332-4797A3, 332-4797A9
They went as high as $400 and as low as $235. I was lucky and found a used trigger on ebay for $65.00.

Part number for rotor disc (warped, window like disc) is 332-4801 and I found one on Ebay for a total of $11.00. I believe it is no longer manufacturered.

Here are the steps:

1. First off, make sure your wires, engine spark plug holes and distributor cap holes are marked with #1, #2, etc. If they are not, White Out or a laundry marker will suffice to mark. Failure to do so will surely leave you wanting to injure yourself.

Common tools neededFor this repair, I will go about it slowly. I have to figure out how take the trigger apart from the adapter. If you look to the picture to the left, It appears as if it was hammered in place.

2. In order to remove the distributor from the engine, First remove the wire leading from the distributor to the other side of the engine going into the ignition coil (gently pull out wire going into ignition coil, its held in place by spring-like tabs). You cannot remove distributor unless you pull out this wire. It has dialectric grease, so it should slide out slowly.

The wires that connect from the distributor to the switch box must be disconnected. The grounding wire has to be disconnected and the 2 bolts holding the distributor adapter to the engine must be removed.
Remove the bolt holding the distributor cover, remove cover and place in a safe place.
You must also remove the spark plug wires from the spark plugs.

After the assembly has been removed from engine, try to clean it as best as you can using a solvent.
Common tools needed3. Remove the clamp screw holding the trigger to the distributor housing assembly. There is a gasket inbetween these two parts. Be forceful but careful. Within the housing, there is a spring bushing.
According to the picture to the left, the housing is the tan colored one. You can see the clamp screw. Loosen and remove screw and bolt, pull the clamp down towards the spark plug wires. Don't "open" the clamp as you will bend it beyond repair, just slide it down toward the round part of the housing.


Common tools needed

Here are the parts. If you look at the tan housing, you can see the bushing dead center protruding out from the housing. The spring is underneath the bushing and comes out nicely and without much force.



Common tools needed

Proper placement of adapter to timing marks on flywheel in order to properly time the engine.
You can see the "white" mark to the right of the picture marking the 23º BTDC timing mark for Mercury 650 (1975). That is the point used to set the "maximum spark advance" stop screw.



Common tools needed

Proper placement of cogs of distributor and distributor adapter as shown to the left. The tab will be noticeably "off" mark if the correct cog is not selected. It may be slightly off left or right when the correct cog is slected.
In order to place distributor in proper alignment, you will need to align pulley "tab" with distributor marking. Align flywheel with the timing tool pointer and it should be pointing to the thick black mark on flywheel (see picture above). Then slip belt onto pulley ensuring all parts are aligned (flywheel, tab and distributor adapter). Then place pulley cover on distributor and screw in place.




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