[As far as the starboard carb running leaner at part throttle, I think we may have to look at the power valves in those primaries. I think the main jetting is close now. Things like the PV opening rate, power valve channel restriction size. These carbs were used but rebuilt. Need to really see whats up with them. Could even be one carb having different size air bleeds, etc. We could order 4 new quick fuel 950's and be done

Theres still more work to do. But its coming along. We're moving in the right direction. Boat loves trim. The more trim you gave it the faster it went. In my opinion, I'd leave the drives turning in (bow lift). The fact its running faster with more trim, is telling me it likes more lift. 15 Degree rake 5 blades are lifting the stern whether out or in. I'd love to try some 18 degree rake smaller diameter 5 blade. Then again, im not brett from b blades, and im not Tres martin. Its all trial and error.

These Flatdecks NEED chop. Your easily a 80+ mph boat on the big lake. I just wish I had more free time right now, to really spend some more time with you on it getting it setup. Boat is friggin gorgeous on the water.[/QUOTE]

10/4 on the oil change . Was completed. It did smell of fuel. Good info

Steve is that your boat??





If so VERY NICE buddy, the wife and I were checking it out. You must have been at lunch at the restaurant?

Its a 38 Flat deck..

The oil never really smelled of fuel even when the plugs were fouled out but better safe than sorry.. not sure why its over heating, I got some good hardware in there.

I can see in my strainers and one sucks all the water out of it immediately (leaner motor) while the other is about half way full, not sure what to make of that except that I enlarged the exit slits in the exhaust on that side so water is getting out faster? Water pressure is at 22psi so it probably has nothing to do with anything.

We`re on the right path, getting on plane is now a breeze, drives are new, no more oil leaks, its no longer a slug, I don`t wanna sell it anymore lol ... just needs some fine tuning and some love.
`m getting a good education on carbs fo sho! They were never my thing but I`ve got a good teacher

Heres the engine vid:

http://33outlaw.zenfolio.com/p13014502/e6dec698b

Sweet vid from the engine room. Do blower belts typically move/wiggle that much or is the starboard one a little loose?

stbd belt is just a tad too loose, but loose is better than tight.

id say both belts could be a tad bit tighter.

KE performance says the thermostat never goes in these ("indestructible") to look elsewhere.. anyone have any issues with these?




yes I know my awesome grounding test wire to the sender isn`t pretty

I will tighten up them belts

Ok, had a few conversations today, and now finally have a minute to sit down and talk about this. It seems theres a lot of misconception on how a power valve works. Im not hear to talk out of my a$$ on this. This is stuff I learned when in General motors training school years ago, and stuff I've played with with boats and car engines since I was 15.

To start. Power valves are designed with different tension springs, to determine their opening rate. A 10.5" PV, NEEDS 10.5" of vacuum to keep it shut (closed). Anything less, it will OPEN. This is why a high performance engine with a lumpy cam, wouldn't use a 10.5, because at idle, it would prob make less than 10.5" of vacuum in the manifold, and we DONT want the PV to be open at idle, or even cruising. Now, In a 454 RV cammed engine, you may use a higher number valve, because the engine makes good manifold vacuum. Holley and others also make high flow PV's for when the PVCR's have been enlarged, and multi stage PV's. Take a look at some blow thru carbs, and you'll see some large PVCR's. They move a lot of fuel thru the PV circuit.

Now, when a PV opens, the fuel is sucked from the bowls, and flows into the same orifices that dispense the fuel from the main jets. What changes the amount of fuel that flows from the power valve, is called the PVCR , or power valve channel restrictions. Some carbs have different size PCVR's, and this can mean the difference of 6 jet sizes worth of fuel, or 10 jet sizes worth of fuel, being added to the circuit when the power valve does open. The MAIN reason people started plugging the rear power valves, was because on a traditionally mounted carb, the fuel runs towards the back of the bowls under hard acceleration. When this happens, the PV is fuel starved, same concept as jet extensions. So to eliminate that , people plugged them. On a roots setup with sideways carbs, there really isn't anything wrong with running a powervalve in the secondary, as long as the main jetting is right.

Most draw thru roots style blower carbs, whether they come from holley or quick fuel, etc, are boost referenced nowdays. What this means is the PV is seeing actual intake manifold vacuum, basically what your boost gauge is tapped into. Non boost reference, the pv sees vacuum on TOP of the blower. This is where things get tricky.

When youre boost referenced, You can run a low number pv like a 2.5. Reason being, at WOT, you'll never pull a vacuum on the pv, therefore it will never close on you at wot. But, non referenced, if you use a 2.5PV, you can quite possibly see 2.5'' or more of vacuum on the baseplate of the carb (where the pv gets its signal from), and when that happens, the PV will CLOSE. You DO NOT WANT THIS TO HAPPEN AT WOT. The reason holley used to provide 10.5PV's in the old supercharger carbs, was to prevent it getting sucked closed and burning up a customers engine.

Now, lets think about what happens in the boat. In a boost referenced setup, the PV is pretty much open at all times except idle speed. When you are on plane, especially in a 38FT cigarette, the PV will never see much vacuum. At 3000RPM, in a 38 Cig, pretty much youre gonna be seeing "0" or dam close to it on the boost gauge. At this point, the PV is open. At 3500, the pv is open, all the way to wot the PV is open. So, main thing on a boost referenced carb, is to make sure the PV is not opening at idle, like MMB stated. These are much easier to tune, because it kind of is what it is, pretty cut and dry.

Lets move on to non referenced carbs like icdedppl has. He has 6.5PV's. in his currently. Both engines have the same jetting, same carbs. However, one is running lean at 3000-3500. Quite a bit lean. 13.4AFR is FAR away from 12.2 AFR from a jet standpoint. From my experience, to drop a full point on the AFR, would take at least 4-6 jet sizes all the way around the two carbs. By removing a power valve, we know we need to up the jets, say 6-10 sizes, or vice versa. At this point, I truly do not know if his PV"s on the lean engine are open or closed at 3000rpm, or 3500RPM. I do know they are open at 4000+ because the AFR are dead nuts after that.. And they should be. Same engines, same jets. Same PCVR's. The signal the PV sees on top of the blower, doesn't change as drastic as if it were boost referenced. The difference of 1 or 2'' of vacuum, can mean the PV is flowing or it isn't. Remember, this isn't manifold vacuum, this is vacuum on top of the blower. You might ask, well if they both have 6.5PV's, why the difference in AFR? Well, for starters, these aren't really precision devices. Secondly, slight variances in engine load, can also make a small difference. One prop having a little less bite or pitch, can load the engine less, even though your throttles are close to same position. Even one blower sucking a tad harder on the carbs. How many of you have ever noticed your throttles are synched, but your boost/vacuum gauges are off a hair? being off 1-2" of vacuum can mean lean or rich when it come to the PV.

Now, to get further deep into this. We know there can be a difference of bank to bank afr's. However, 13.4 and 12.2 is a large difference. We aren't talking 2 jet sizes here. On my 420 straight lobe rotor engines, my AFR's are .1-.2 different. Not even enough to worry about. My buddy's 509's with 871s were slightly more different, but not a full point or anywhere near it. It was maybe .3-.4 at most.

To sum it up, my plan was to install 8.5PV's. This will make them open sooner. If his target is say low 12's at 3000 (no boost), and gradually working his way to low 11's at wot, I think he's real close right now. I don't think adding more primary jet is the way to cure the 13.4 AFR. He'll probably need to go up 4, 6, or even 8 primary sizes to get that number where it needs to be. Then, it will be pig rich again, and only way to compensate is to then pull jet out of the rears. At that point, he'll have went from a very conventional 86/96 number, to a 92/90 setup with rear pv plugged. That just isn't a correct setup.

So, to go back to before this thread was even started, simply installing a 8.5PV and putting a vacuum gauge to the baseplate of the carb, would have told us something. When a PV opens, things go rich. Way rich. Like a point or more, which is exactly what he needs. Simply opening and closing of a PV is like adding 6-10 jet sizes like I said.

He went from 9.6 AFR at wot, to 10.8-11.0 just by plugging the power valves in the rear. This would have been equivalent to pulling 6-10 jet sizes out of the rear. see where im going with the full point of AFR change?

This isn't really a new idea. Automakers have been using LAMBDA and reading oxygen content in cars for decades, long before fuel injection. Back in the day, when the power piston opened, the AFR's came down, to provide power enrichment. To make power and keep the engine safe. They still do this today, only its EFI. Take a new gas EFI truck, and you'll see it will cruise all day at 14.7AFR. Then when you mash the throttle, it goes to a "Power enrichment" mode, somewhere around mid 12 AFR.

Also, after rewatching this video, I see different numbers than what dan posted originally. Heres what I see

3000RPM =Port 12.2 Starboard 13.3
3500RPM =Port 12.3 Starboard 13.3
4000RPM= Port 12.1 Starboard 12.2
5200RPM= Port 10.9 Starboard 11.1

I have no reason to believe the sensors are inaccurate, nor why the banks would differ so much at 3000 and 3500, but almost equal at 4000 and above. Something is making the starboard lean while its running on the primaries. without talking air bleeds and what not, we have two things here. Jets and a Power valve. Obviously the jets are moving fuel But is the PV? We don't know. . I suggested power valve change, and retest. Everything else looks fine to me. I'll leave it up to Dan. This really isn't too complicated. Now, dialing in a carb on a blow thru setup at 17lbs of boost, referenced fuel psi regulators, carb hat angles, shimming power valves, and all kinds of trick stuff. I will post a picture of that dyno sheet that Mike Tkach and I worked on together. AFR from 3000-6000RPM that didn't change much more than .4 over 3000RPM difference from almost no boost to 17lbs. That takes a little work and can get really complicated. We tried getting numbers like that using a prosystems carb, and there was no jetting combo in the world that could have cured 10.0 afr at 3000, and high 13's at 6000. It just wasn't the right carb for that much boost.

As far as the carb's randomly popping thru the intake at 1800ish rpm getting on/off plane, I think that is due to the idle feed restrictors nickerson installed in these carbs. While they idle very smooth, with no surging, the idle circuit is imo lean. Dan tried going "in'' with the mixture screws, and it popped like a sob, and wouldn't even plane. He called me, I told him back them out a 1/2 turn each, popping stopped. I do not have idle feed restrictors, nor do I even have 4 corner idle. No popping on my setup. You cant be lean at 1800rpm with 32* of locked timing, its just gonna pop thru the intake. It wants the fuel. The idle circuit is still in play contrary to what some think at that rpm. It has to be. There just isn't enough airflow yet to command fuel entirely from the main circuit just yet.

Dan, im not trying to suggest my way is the best way. Im just trying to give you a idea on where im coming from with my suggestions. I've played with this stuff a little in the past too. I don't wanna see ya spending the next month trying to chase down lean spots and wear out the screws on the carb bowls. you've done enough wrenching, its time to get this thing going and have a beer. If im wrong in my suggestions, I'll be glad to share it, and buy whomever a beer or two when its dialed in. Popping is unacceptable, and lean at 3000-3500 is unacceptable. You spent the dough for the wideband and 02 bungs, lets keep using them. It LITERALLY will take us 5-10 minutes to pop the bowls off on the water, install the higher number PV's, and get back on plane to see what it did. IF it doesn't help, you put the 6.5's back in, and move on to changing main jets. Just like I suggested at your house when we pulled the rear bowls and found the PV's along with the big jets. I said lets remove the PV's and see how it runs. We went from cruising at a 12.4 AFR, mid 9's over 4000AFR, to 12.4 and 11.0 WOT AFR. One change at a time my friend.

joe,if i were a betting man[and i am]id bet a case of beer that 8.5 or 9.5 power valve will cure the problem,change them in both engines.dan,as i told you a few days ago,listen to joe and do what he sais and you my friend will be a happy boater!

FU%$@ you guys I`m going to put an EFI system on it and call it a day!!!!!