502-spark plugs
 

I have an 1996 502 Mag. Recently changed spark plugs from Ac-Delco to NGK. I have seen a 5 mph lost. Is not missing. Motor is not running hot. All wires are connected. Only thing I can think of is plugs may not be gapped correctly. Still see same rpm's. Any other thoughts-suggestions?

Did you put them in out of the box? I just put NGK's in my boat and found them to be gapped to close, about .25 out of the box. Check the gap they should be .35-.40. I still don't think that would cause you to lose 5mph though. If the rpm's are the same I would think it is the speedo. Just my .02

From the advice of a few freinds with 502's. I am now running the AC Delco rapid fire #1. Wow!!:eek: What an improvement!!. No more black soot going thru no wake zones, better starting, and maybe, just maybe... 50-100 more RPM's. been running them for about 20 hrs now, and very impressed. Just my .02 of course;)
Happy boating

I have been running Rapid Fire #1's for 2 summers. They did reduce the soot on the transom and motor runs great. (454 mag mpi).

Jan

Plug part number
 

Is there a part number for the Rapid Fire # 1's, or is Rapid Fire #1 all I need to look for when I pick some up ?

Engine is a 502 and the transom is black after a no wake zone.

Yes just ask for AC rapid fire #1 that is the part number. I just got 8 for my 454 mag. They made a difference in starting. Usually the engine would fire and then stop then on the second turn of the key it would stay running. Now it starts and stays running on the first try.

Yes, Rapid fire #1 is the cross for the MR43TS. And if your wondering...:rolleyes: .Yes it's a Stainless steel plug with a platnum electrode.

Thanks for all the replies. Been on Lake Erie to a Put-In-Bay get away. Maybe I will try the rapid fire #1's.

dude if your turning the same rpms at the same trime angle w/ the same prop...your going the same speed!!!...stick to the NGK or the MR's....

That has been my thought the whole time, I wanted to bounce this off you guys for your thoughts too. Here is a thought to you Audacity...Is there something you do not like about the rapid fire plug? Something I should know?