Holley Carb. Power Valve question

It's getting time to rebuild the Holley carb on my 1990 Ski Nautique. When it was done 5 years ago, I recall installing a 6.5 Hg power valve, but can't remember the pros and cons of using it vs. the 2.5 Hg power valve that comes with the rebuild kit.

Will someone please opine on the differences?

Thanks!

Bri892001 wrote: The 6.5 will basically run richer.

Kinda sorta.

All the Holley PV's flow the same amount of fuel. The difference between them is how much vacuum is required to pull them open. The higher the number, the less vacuum is required- thus, it opens easier/sooner.

The thought is that (to an extent), the higher the # PV, the more responsive the engine will be. The trade off for that responsiveness is a bit of fuel economy.

Gottaski can explain this better than I can.

Im running a 7.5 in the '90. I couldnt tell you if it made a change- I did a bunch of things all at the same time. I can tell you for sure that the boat is plenty responsive!

I've rebuilt a few over the years , and found the 2.5 lacking.

With the 2.5, the carb wont come out of lean cruise till vacuum is 2.5 inches or less.
However load is maxed when you come out of the hole, the engine needs the fuel then, else there is a subtle , yet reproducable dull spot 2-2500 rpm or so. The extra fuel from the pvcos is critical under high load, nobody changed the mains, nor lightened our boats, but suddenly carbs and kits are shipped with the 'leanest' pv that exists!
I think it some half baked idea to use mrarginally less fuel.

After 25 years, it was time for a fresh carb for myself, bolted on, set idle mix, tried to tune out that dull spot again, then just opened it up and threw a 6.5 in and its as smooth as an fi engine.