502 Mefi distributor cap
 

This past season, my motor developed an idle that was a bit lopier than normal. I don't have stock cam, and it always was a bit lopy at times, but not constant. The last time it did this, it was a timing issue; which had changed a few degrees for some reason. I decided it was time to change spark plugs, which i did with no change to the idle. I did a visual check of the cap/distributor clocking, and it hasn't changed. I haven't actually checked the timing yet, but will. If memory serves me correctly, it was set at 9 degrees in base timing mode; as it idled best there. I'd like to change the cap and rotor as it has been on there for approximately 400 hours. Wires as well. The current cap that is on there is gold. I'm noticing that the stock mercruiser cap is black. I havn't pulled the cap to see if there is a manufacturer stamp in it, but does anyone know what it may be? Should I go with aftermarket or stock merc? My engine is slightly modified, putting out approximately 465hp.

Gold ?? Ive seen tan, just put on the stock black cap, it will cross to an AC Delco part #

I found this thread when doing a google search. Funny enough, this is the prior owner of my boat inquiring about the same thing. Not a lot of suggestions however...

https://www.offshoreonly.com/forums/...2-mag-efi.html

It may be tan..... I haven't looked at it since October..

You should have a EST (808483T3) distributor but could use the serial number to verify
Suggest a Merc cap and rotor

https://www.mercruiserparts.com/bam/.../31912/4854/70

i'm thinking this is what is in there..........

https://www.holley.com/products/igni...ors/parts/8132

Base timing is 8 BTDC, and depending on which MEFI you may need to manual increase the rpm

When you said gold I was thinking maybe tan which is Accel, as you found out. I’m sure this will open the can, but, I went with a MSD cap. Nice heavy thick cap and rotor, and DUI wires. There heavy wires with sleeves. Not listed as marine apps but if you get the ones for big block Chevrolet, “under header” they work. I think BUP on here has a source for some marine specific applications on wires.

Ok, thanks.

I got caps, rotors, new ignition coils and pick up coils from BUP for my 502 MPI's. No China eBay crap either. He also has Marine specific Moroso ULTRA 40 wires that are sweet for this app. Highly recommend him for all of this. :ernaehrung004:

Thank you DD for putting my name on this ^^^^^^ . We actually came up with improved rotor design for 2020 all made right here in the USA. The cap you are looking for and WANT should be brass terminals underside and on top. Meaning brass all the way thru. Also there is 2 different versions of rotor designs to use for the EST distributor apps. The 454 and the 502 used the EST set up. Also extremely wise to buy a new coil. for the coils here again for 2020 I have an USA made coils. Important info about coils - you have to match the primary and secondary resistance of the coils per what the ignition system was designed for. Everything I have is all done & made here in the USA. Since everyone here supports America why buy from other countries ???


If anyone has questions about my coils ASK VOODOO ROB he has my specific coils on his Merc racing 700 sci engines. You can not get these coils anywhere else. NO BS. Yes you can get the look a likes but they are not these coils that I have made.


Also for the record will add more info about caps and rotors ---- the T bolt IV and V cap and rotor for Merc thunderbolt ignition - I only sell Merc brand, cap and rotors --- why because they are made in the USA by merc themselves in Florida. They do make the best cap and rotor for the THUNDERBOLT ignition set up. And these are brass all the way thru for terminals on the distributor cap.

Why are the coils recommended to be changed? I haven't heard of that before now. Only cap/rotor/wires/plugs.......

Thanks.

Thousands of good coils are tossed every year and mostly because there cheap and easy. Have only seen a few that really need to be changed

If you work on lets just say 300 boats per year. You will find bad coils more than enough no matter of the ignition set up.


So let me ask how is anyone testing coil output to determine if its good or bad ?? And coil output spark energy ?


Also for the record a coil that is not warm with heat can test good a lot of the times.


Also the oil filled coils go bad all the time as the oil seeps past the inner tower structure. for a jist of info.

thanks for the information