Why mercruiser 3.0 spark plug gap increased from 0.035 to 0.045?

[jack black]

According to the owner manual for my 2003 model, it's supposed to be 0.045 (1.14mm). However, some older merc manuals covering the Delco EST Ignition (I think I have this one) talk about 0.035 (0.9mm). If one looks up aftermarket plugs for this motor (like NGK) they are listed as either 0.035 or 0.039. When did the switch form 0.035 to 0.045 happened and what was the reason for it? The reason I ask, recently coil went bad on me and I'm wandering whether keeping sparks at 0.035 would be easier on the replacement coil.
Thanks!

 

[Fun Times]

To help ensure what "your" specifications should be for your engine model, check on top of the flame assertor cover (carburetor cover) to see what the gap specifications should be.

 

[MikDee]

They did the same thing with cars, trucks, & motorcycles, ever since they introduced electronic ignition on everything. 1975 on land vehicles. Gap went from average .035" to .045" across the line. I guess because of better fuel burn, & economy. All electronic ignition systems deliver a better, stronger spark.

 

[jack black]

To help ensure what "your" specifications should be for your engine model, check on top of the flame assertor cover (carburetor cover) to see what the gap specifications should be.

My "specification" is 0.045. But this is not my question.

 

[jack black]

They did the same thing with cars, trucks, & motorcycles, ever since they introduced electronic ignition on everything. 1975 on land vehicles. Gap went from average .035" to .045" across the line. I guess because of better fuel burn, & economy. All electronic ignition systems deliver a better, stronger spark.

Yes, but like I said, it used to be 0.035 with electronic ignition and it's 0.045 now with the same ignition. So, what changed?

Reference on 0.035 with electronic ignition is on the page 23 here: http://www.boatfix.com/merc/servmanl/13/13b4r2.pdf

 

[dubs283]

So, what changed?

timing

the timing for the 3.0 has slowly been retarded over the years, this is due to the casting for the block - its been the same for more than 40 years, started at 6 BTDC now its at 2 ATDC - reason is blowing head gaskets