TOPIC: 1975 Merc 1500 Distributor

I have a 1975 merc 1500 that might need a distributor, anyone know of someone that may have one or can rebuild one?

Thanks,
Tim

Tim, give us an idea which part of the country you are in. There are a few folks that could help you with that.

I am in the mid michigan area (Lansing) but spend alot of time in west michigan (Grand Haven/Muskegon). I see a few on ebay but not 100% sure I would get the correct one.

Thanks.

1500 J may be able to help you out, definitely a 1500 expert.
Sorry, Milkdud on this forum.

This 115hp distributor on eBay, $246 shipped, would work on your 150hp as well:



I didn't see any cheaper. If the distributor is missing, this would be a decent option, since it would have all the parts you need. Or find a parts motor on your local Craigslist.

However, the problem with a used distributor is, you don't know how much life the trigger has left. It could run for years with no issues, or fail the next day (or week or month).

If your 1500 has a bad trigger, but the rest of the distributor is intact, a better bet would be to rebuild it using this CDI Electronics trigger kit:

$281 shipped.

The kit comes with the bottom bearing; you'll want to replace the smaller upper bearing while you're in there. Also replace the snap ring, as they are prone to rust/breakage. The chunks of snap ring circulate inside the distributor and break the trigger pickup.

I haven't seen a cheaper price than the above eBay vendor; you could always do a parts number search if you wanted to check for yourself.

BTW, here's a good test for the Merc CDI ign system, to check for other problems besides distributor:

MERCURY BATTERY-POWERED CDI TEST FOR DISTRIBUTOR MODELS

This test is for the 332-2986 switchbox used from 1967-1978 on all the inlines.

This test assumes your coil is good (problems with this style of ign coil are rare).

DISCONNECT BATTERY

1. Turn off ignition;

2. Disconnect all 3 distributor wires on the Port side of the switchbox (and the “mercury switch” if present);

3. Remove the HV lead from the ign coil to the center of the dist. cap (remember it unplugs from the coil and unscrews from the cap);

4. Reconnect the HV lead to the COIL only;

5. Position the free end of the HV lead approx. 3/8" from ground (block, shrouds etc), and find a way to hold it there;

6. Jumper the brown and white terminals on the dist. side of the switchbox to each other.

RECONNECT BATTERY

7. Check that you have +12V at the red terminal (even with the ign off);

8. Turn on ignition and verify +12V at the white terminal (same side as the red terminal);

9. Ground the black terminal on the distributor side of the switchbox - this should cause a spark each time you touch ground.

If you get spark with the distributor bypassed, and it won't fire with the distributor connected, the trigger is bad and the entire distributor housing assy must be replaced.

If you get no spark using the test, the switchbox is probably bad. In that case, be sure to check for correct power on the switchbox, check all connections, and check the coil's resistance to make sure it's OK.

HTH............ed

Thanks for that info, ed-mc.

I started to take apart the distributor and I cant get the nut off the rotor shaft, I know the rotor does not come apart from the shaft. Looks like another "special" tool might be needed. Also the disc is badly corroded (green) so I assume its copper? And is that a problem?

bend the tabs that lock the nut they are in the notches. then just unscrew the nut channel locks with a rag to protect the nut.

I found an easy way to get the rotor nut loose after bending the (2) lock tabs down was to use a 3/8"-drive butterfly impact wrench, while holding the rotor-end in a gloved hand. Usually they're not so tight that they won't bust loose the instant you hit it with the impact. But you should be able to get a deep socket in there on a ratchet and loosen by hand, as well. Just be careful not to damage the rotor (it doesn't come off the shaft, BTW), an extremely $$$ part!

The copper "chopper" disc gets replaced anyway, so its condition isn't important if you're going to use the CDI replacement part. It comes with a steel disc which must be used in order to work with the "New & Improved" CDI-design magnetic pickup.

Some Good Words: Once the locknut is removed, there's a spacer that comes out. After that, nothing holds the rotor/shaft assy in place except for its slip-fit thru the bottom bearing. It might be a bit tight, though. While holding the copper disc so it doesn't move downwards, tap the top of the rotor shaft with a plastic mallet or similar non-marring tool. The rotor should come down out of the lower bearing i.d., leaving you with the old trigger housing (with old bearing retained by snap ring).

The CDI replacement trigger has really good instructions, so I won't repeat them here. Be sure to set your belt timing once reassembled, and torque the flywheel nut to specs.

HTH..........ed

Don't forget to mark the side of the chopper disk in case you do end up re using it. It will fit both ways but only work one way.
felt pen works fine.

Ok, I have the rotor shaft out of the housing, chopper disc is going to be replaced, but the wiring is in bad shape. Of the three the white is the worst, badly frayed where is comes out. Not sure about a repair. Maybe solder??

Thanks for all the advice.

Tim

Going back to your first post, you said you "might" need a distributor. Was that based on looking at the frayed wires or was that because you had no spark? If you had no spark and you trouble shoot it to the trigger then soldering those wires will not help. Corrosion has likely gotten to the encapsulated components inside the distributor housing, which is what those wires connect to.

Sorry, I should have been more clear. Lost compression in the #1 cylinder, other 5 had 125psi. I think it was starting to over heat??? So I thought I would rebuild it. That's when I noticed the distributor had some corrosion on the disc and the frayed wire. Block is getting machined and a new piston. Motor was running good, no real issues.

Thanks,
Tim