I was wondering if it would be a good idea to up my primary jet size by 1 number from 78 to 79 due to the cooler weather in my area now. I am running 78 pri 86 secondary with a 6.5 pri PV. through out the hot summer and now since the air temps are below 65, I was considering a step up in jets. Holley recommends 1 jet size for every 35 degrees increase or de-crease.
Is this correct??

If its running fine...then leave it alone. 1 jet size is nothing, and I'll bet you wont see/feel the difference. Truthfuly, its too much work, and new gaskets, for 1 jet size sir.

If you want you can jet up, 6-10 jet sizes to richen it up for the winter. Cant hurt the motor.

Except when it washes the cylinders, fouls the plugs and starts taking the first layer of metal off the rod and main bearings 10 jet sizes is ALOT, Smitty

10 jet sizes will do all that damage,slow the boat down,and use more fuel,DONT DO IT,back in the old days,when cars came with carbs,you did not need to change jets for winter.unless you plan on useing it for an ice breaker,it is just fine.

6-10 jets sizes ??? WTF are you insane....

Man, tuff crowd. With cold dry weather maybe another 2-3 jets sizes max in the secondary to even. That would be pretty cold weather. So subtract that off the 6-10 you have 3-7. 3-7 sizes rich from perfect won't cause all those problems, not never, period. It will cause sooty transom and much poorer performance on top assuming you were jetted right in the summer. So don't do it. Leave as is or better yet get an a/f meter and know what is what.

Leave it be and just run it,the cooler crisper weather will ripen her right up. 10 jet sizes OMFG

How radical of an engine? I can't imagine needing to change the jets for cooler weather unless it is a setup that is already on the edge where one or two jet sizes might mean meltdown..