Al,i'm going to jump in this for your latest question,when you free rev a motor(no load in driveway) the vacuum will go way UP (as long as your reving it steady). If you had your throttle linkage unhooked and blipped it with your hand on carb real quick,you would see the vacum drop temporarily then rise but it wouldn't tell you anything anyways,Hook your vacuum gauge to your carb with six or eight feet of vacuum hose and run it up to your helm temporarily if you want to see what it does under a load,Smitty

AL smitty was right .running the engine with no load the vacuum will increase but under a load the vacuum will drop when you go in gear thenn when you add throttlethe vacuum will increase for rpms then as the load gets greater the vacuum will drop eventuality to 0 by wide open throttle. run the vacuum gauge on the next sea trial and you will see which way to move your power valve . but if you are to rich on the pri side the idle vacuum will be lower

Sea trail results are in and based on what I think I've learned from you guys so far, they look way to lean to me, check out this photo. This is with #76 in primaries and #86's in secondaries; both have 6.5 PV's in them. Here's some under load reads:

Total time: 34 degrees at 3000 rpm, set at no load, both engines

Vacuum readings:
Port Eng. Starboard Eng.
Idle in gear, 900 rpm 18 19
2000 (load, nose way up) 9 10
3000 (load, on plane) 6 5
4000 (load, on plane) 4 3

The left plug in the photo (from #7 cyl., port engine) was new, never run at idle except for a few seconds, then run at about 4000 rpm for about 3 minutes. The right plug in the photo (same eng. and cyl.) was run from dock to the lake (say 5 minutes at idle) then at about 3100 rpm for about 3 minutes.

Obviously, the porcelain on both plugs are stark white. The ground electrode on the left plug (run at 4000 rpm) shows considerable bluing and the center electrode does too. The right plug ground electrode is not nearly as blue but still shows some blue, the center electrode is about the same.

To me, this says we're still very lean in the mid range and very very lean up in the 4,000 rpm range. Also, it appears those 6.5 PV's would not be kicking in till somewhere around 34-3500 rpm on the port engine and 32-3300 rpm on the starboard engine. What's the deal with the different vacuum readings at the same rpm? Even though I have them as close as I can get them, could it be that total time may be just a tad different between the two or would this be the result of something else. Let me know you thought but I'm thinking going back up in the 86 range on primaries and 90's on the secondaries and leaving the PV's alone for now. Al

A Great engine information system that I use in both my airplanes and Boats! this used with a good three wire Air Fuel ratio guage is great!

model 2004 EIS http://www.grtavionics.com/

A/F guage http://www.turboimports.com/gredairgaugk.html

I had CMI build in a dry port for my o2 sensor. and EGT ports.

Bryan

al what did the plug look like down at the base of the porcelin the top only show color after a cupple hours running time.when we run a motor on the dyno for a day they barley show color on the top . thr eletrode will turn a rainbow color till it gets covered in carbon. change the power valve to 8.5 a run the boat agian. add fule addative of some nature and the plugs will color quicker. the jetting still should be close with your combiation

formulaz583, the spark plug attachment/photo is at the bottom of post #50. Looking all the way down the porcelain, both of them are white all the way down. The boat comes out of the hole good and runs better than it ever has, I have to believe that has something to do with finally getting the total time up to 34 degrees, the idle timing has got to be up around 20 now as opposed to 16-18 at best in the past.

Everyone seems to be running high #80's on primaries and #90 to #92's on secondaries. Back in post #33 when I ran the 88's & 92's, the plugs did appear to be going towards gray but I swear it felt like it was going to foul the plugs getting to the lake and back at idle. On the other hand, having now marked the balancer and having moved the total time to 34 degrees, it must have been running about 32 degrees or less total timing back then, would that have made a difference on the idling characteristics?

These vacuum readings seem to be higher than everyone's, what up with that? Why? I agree, if the PV's are going to pass gas in the mid range, I've got to go to a 9 or so, but again, that sounds very high when compared to what everyone's running. Have you guys heard these high vacuum readings before? Are they unusually high or just a bit higher and no need to concern ourselves with why they are higher? If I heard CMS right back in post #48, jetting effects vacuum, does everyone agree with that statement?

It's hard to believe they ever ran with the #71's & #80's if this is range they need to be in, I mean your increasing the flow capacity by about 55-65% according to the Holly jet charts when you go the the 88's & 92's. But, unless there's something new, I think it's best to at least go back to the #88's and #92's and get some vacuum readings there with the new time, check the base of these plugs again and go from there.

al the vacuum readings are high but you have a smaller size cam . hte .050 numbers arent that that big and the cam is on a 114. cnt. line which will give you a higer vacuum reading.please don't go to 88. pri and 92. sec. you will wash the walls with that jetting. if you must go up try 80.pri and 90. sec. but I have never put that much jet in a 4779. card even in a blower motor which made 745 hp . I only ran 78.pri and 85 sec. one of my race boats runs a 468.cid engine with a 4779. and 562hp . I run 75.pri 3.5pv and 85 sec no pv. and the engine package has been working just fine

I hear you load and clear but with these plug readings something has got to chance. Based on limited knowledge I've gain from you guys on plug readings, they're lean. I certainly don't want to wash the walls either, makes no sense to save the heads and destroy the rings. There's got to be something else going on here with the plug color being what it is and at the other end of the spectrum, them not wanting to run at idle with big jets???? We've got to at least change the PV to a higher one if we are going to run the 76's & 86's because they're not opening til up around the 3400 rpm range and then only barely.

change the power valve to a 8.5 will make it opne around 2350.rpm to 2500rpms dobble check your fuel psi while running you need at least 5.5psi at 5000. rpm and check fuel lines etc. one more time the plugs will color eventuly . it takes longer than 3to 5 minutes to color the top of the plug look at base of the porcelin it should be a gray band around it after making a run on them. due you have a egt metter you can install in the exhaut system. to help you tune your engines,

Alcor,you need to check your fuel presure real well,ive ran a 4779 carb on a drag car (i know that a boat needs to be richer but NOT 12-14 jets richer). If for some reason you are getting some air thru jets mixed with fuel (low presure) then you'll band aid this deal with a ton of jet which isn't correct. Besides,if a motor has real good vacuum it pulls fuel(strong signal its called) thru the jets and booster venturis real well.People have been known to jet up a big carb on a motor with radical cam and heads to make up for low fuel signal and vacum,(the opposite of what you have). I would suggest also rigging some kind of air fuel mixture gauge or egt in your exhaust if at all possible,don't waste your money on gaffrig egt's though(i have them on #7&#8) on my boat and they read 200-250 degrees hot. I would pictur your eyes watering,plugs loaded up,transom black with 88 primarys in your boat(as someone said earlier-6-1 stoichametric fuel ratio!!!). Let us know what you find,Smitty