That was a thought earlier in the thread.

Definitely boat dependent as some boats are under a lot of load even while ‘cruising.’ A vac gauge can be a good friend here.

Not so common to see vac cauge in a boat with N/A engine, i wonder why. I have one in my fresh build.

Yep, I brought it with me but got lazy and just wanted to play a little. Hooking it up is a ***** too because all of the vac ports were plugged. I could have gone with the 8.5 and probably been good to go, but I didn’t want to overdo it.

That is pretty much what I saw yesterday. Port was a few tenths lean compared to starboard but pretty much exactly as described.

About the only place that power valves make sense in a "performance boat" application is during the "accelerate to planing speed" range. You know the one - you push the sticks up to 2,500 rpm and leave them right there. The boat pops up on plane, then runs on up to 3,500 rpm at the same throttle setting. As the boat comes on plane, you have low vacuum and higher cylinder pressures. Once she's up and running free the vacuum climbs.

A vacuum gauge along with an AF readout is very helpful in figuring out your jetting and PV sizing.

And for me, a 3400 rpm cruise without any opening of the secondaries is fine to see AF in the high 13 or even low 14 range if the boat is fairly light.

With Holleys though, if you are into the transfers at all at idle, you may need to drill a small hole in the butterflies. Idle circuit should take care of your idle. If you are into the slots, then you're compromising your off-idle mixture.

What qualifies as a “light” boat? I’m guessing a 31 footer weighing 8500-9000 pounds isn’t considered light, but maybe I’m wrong.

I’m seeing as described. Digging into it to get on plane and then they settle into about 13. I want to say that was on the primaries (after on plane) but I was trying to pay more attention to the gauges and the “Cape Henry Slop” vs stick position. Memory says that it felt like I was against the point where you have to push to begin opening the secondaries (it’s definitely noticeable). I don’t have a problem ditching the power valves if that’s the better way, but I need to really check the vacuum while running to be educated on the next step to take, if any.

Idle transition, I’m not into the transfer slots. Running against the outgoing tide to keep speed up in the no wake is a little rich but not too bad. If I need a little more air, I have the “idle-ez” that’s part of the Demon setup. So far so good.

Next weekend we will be working on the Cig to finally get that thing done, but I’m looking forward to more running/testing. The new power is really fun!

Yeah. While you are tuning it's very helpful to have a vacuum gauge to look at.
Setting idle mix is USUALLY 1/4 turn richer than max vacuum. On a 4-corner carb, adjust all 4 evenly. An HP series Holley has an idle air bypass adjustment thru the tapped hole where the threaded rod for flame arrestor screws in. Not sure which Demons do/don't have this feature. It's handy.

I have not seen the idle-ez do too much but I imagine that it's purpose isn't to flood the system with air. Instead, just a little bit of a vacuum leak to help lean out of the idle a touch without exposing the trans slots.

I like the carbs. Some crap quality out of the gate was seen, but I corrected it. They had some good ideas with the Demon, and it looks like they took some of it and applied it to the HP Holley carbs.