wannabe

My manuals are offsite, what is the gap on the Merc 400 (454 ci). I assume it is around .045 or so?

Wannabe

mrhorsepower1

I would gap them at .040 if using stock Mercury ignition system.

wannabe

The engines have MSD systems, not the thunderbolt. The .040 sounds about right. Thanks.

Roger aka Wannabe

Griff

With the MSD's you should probably go .045.

mrhorsepower1

You can go .045 with MSD.

wannabe

Thanks Dean, looking forward to the quote on the 540's

Roger aka wannabe

mrhorsepower1

I will have it first if the week. Thanks for your interest in our product!

Best Regards,

Dean Gellner

nwimbush

Dean - I wanted to thank you for the help and advice I've extracted from your posts since I joined OSO, you are always providing the voice of the seasoned pro...I did take your advice and go with SRP pistons as part of the Eagle 11111 rotating assemblies for my 454's (now 496's). 9.1:1

I recently adopted two Jacobs Marine Master ignition sets from an OSOer, and the docs tell me I can add up to .015 to the stock gap (typ .035?). The documents also push the benefits to spark plug indexing...8-10hp...do you have any experience with this? It seems like an easy gain.