Ran some today and with cooler weather the jetting seemed to be a bit lean in cruise and into the secondaries.

Idle is rich but could have been the trans slots were a little more exposed. I closed the butterflies some and it seemed to be happier. Very snappy.

Cruise AFRs in the mid to upper 13s and pretty much stayed that way getting into the secondaries. I think we saw 14s here and there during cruise.

Jetting is 86/93 with a 4.5 pv.

Step up the PVs to 6.5s or more and see what happens? Increase jets a couple sizes?

What about removing the power valves completely and running 96s across the board?

Engines really begin to pull like raped apes beyond 3800.

Thoughts?

yes.

Glad to have the meters. Had I not, I wouldn’t have know about the lean condition during cruise. I cannot say for sure but WOT throttle testing would have had me looking at secondary jetting.

The engines have good power, oil and water temps around 170 (I think water temps are actually a little lower… the top hose from the stat shows 148), oil pressure 55-60 with 15w40. Engines appear very happy.

13s at cruise… thankfully I really didn’t go anywhere with it other than to test.

How many are running like this? Seems like a gamble. Or am I making too much of it?

What size carbs

Demon 850s.

Does it have one power valve on the primary side only? Or does it have one on the secondaries also?
Do you have a vacuum gauge hooked up to know how much vacuum is being pulled at idle, cruise, wot.

I have not run her wide open yet. Just going off AFR readings at the dash, idle through mode range. I did push a little and AFRs remained the same. Coming off say 3800 to 3500 my buddy said he saw 14.1.

Idle vacuum is right around 10 inches. Might be a little more since the timing has been dialed in. Next time we go out, I’ll measure.

*Edit*

Power valve in the primaries only.

Do you know if your cruise vacuum will be low enough to actuate the PV's? If so that will richen things up, as you want. And then if it's too fat at higher rpm, you can take out some jet from the secondaries.
My setup does a similar thing, as I increase cruise rpm my mix goes way into the 13's. But when I get on it, the thing takes off and the afr is perfect mid 12's. I'm probably going to do a richer primary jet cause that's literally where I cruise most of the time. But I'll also lean out the secondaries the same amount to try and keep a nice afr at big throttle openings.
AFR meter and vacuum gauge is the best way to observe.
Some twat saw my vac gauge at the ramp and thought it was funny. Ain't there for you buddy.

Stepped up the power valves to 6.5s which is original for the Demon 850. Not much of a change. I didn’t measure vacuum so it really was a shot in the dark. I will next time. The engines were running great and we were a little harder on them escaping this evening before coming in. I may leave them at 6.5 and add jet to the primaries as mentioned.

Powervalves in a boat never made any sense to me. If you`re going to dump 6-8 jet sizes worth of fuel all at once why not just increase the jet sizes accordingly and get nice even fuel map instead of a gas dump?
I could never get a nice even fuel map till I got rid of the power valves and just went bigger jets.