How are you coming along. Are you still running rich and have the stumble? I really don't think your over carbed. You could perhaps get away with the 9022 - 800 cfm however I don't think the 850 if properly tuned would give you the trouble your having. I can't remember at the moment if you rebuilt it or not. If not I would get a kit and do it. Make sure you soak the entire carb/parts in cleaner over night and blow threw everything extremely well. Did you buy the carb new? Perhaps a previous owner has changed out the plastic cams to taylor their needs. What are you using for ignition? Also any test you do especially pertaining to jetting always do it with a new plug in number 8 cylinder at the very least and check it every time. That's most often your hotest cylinder on a BBC. What size squirters do you have in the front and rear. Also you'll want both front and rear plates cracked at an idle. try and keep both the same. There is a lot of info on holley carbs when you google it. Information from experts to help you tune as well as holleys site. Just a thought. I would imagine you have a lot of boater friends around the area. See if you can borrow a couple of different carbs to help diagnose any problems you may have. The carb calculators are OK however I have ended anywhere close to the number it gives you. That's kind of an old time theory. Marine engines always like carbs a tad on the larger size. Believe it or not to large of a carb can actually lean out at WOT. They get lazy a little lazy so to speak and tend to not pull is much fuel through. As mentioned above I would also try and prop it for 5400 to 5600. Your duration @.050 - 236/245 will like the higher rpm. It will seem like a whole different boat.

Thanks mate,
I've got a 23P Rev4 on the way to try and get the revs up a bit.
I'll check the squirters but I think they're good. The cams on the accel pumps are okay (I had them checked too.) The carb is virtually brand new and I just had it rebult again anyway. I then tore it all down and confirmed what was done and put all new parts & gaskets in again just to be sure.

I think from what I've read so far, I've been running it rich in an effort to compensate for a porely established base idle which I set using the primarys. I've re-adjusted using the secondarys and leaned it out a bit. I've managed to get it to idle now aroun 800rpm pulling 12 inches (at best) with about 2/3-3/4 turn out on the screws. I'll put her in the water again when my new breathers show up and give that set up a go.

Thanks all, I have learned a great deal which hopefully will help me hit my goal of 90+ mph!

what flame arrester ? seen those restrict and cause a rich condition, seems rich by what you are saying....can you crack you hatch and run the boat ? have seen boats that do not get enough air into the engine compartment..basiclly chokes the engine..would show up as rich...Rob, ps did get a intake, thanks for your offer !!

I don't think air flow is an issue.
Massive scoop and equally massive oval billet air cleaner with K&N filter. I think mixture or jet size is my bain at the moment so I'll scew with that till it's sorted and see how that goes.

90+ - I think you been chasing to many Kangaroos and drinking to much of that goofy beer you have over there. LOL... Good luck though. That was a good point made above in regards to the flame arrestor however sounds like you got that covered. I have to look back however what is your total timing?

34 BTDC Total. Start 14 Deg BTDC, 20 Deg curve. Could that be a problem?

I would say your right on. Sometimes I have seen advance curves vary even with the same modules. Just wanted to make sure you did check total advance with a timing light. The only time I check base timing is when first start up after a rebuild.

ghostrider did you do wt i told you to do run the enginge at 3000rpm then put the timming on 36deg. . when you run it at 3000 your timming will be at full . ..

I am not familiar with the crane HI 6M ignition however I am assuming that total advance is by 3,000 or is this adjustable?

Ghostrider, how do you like the Crane Ign. box? I was thinking of adding those to my merc TB 1V ign.

I've checked the engine under load at 3000 and the timing is spot on. That's the joy of the HI-6M, it set's the advance curve with the pre-selection of one of the built in curves. I have mine set to position 6, N/A motor, 14 deg BTDC start, 20 Deg curve. You can also select from 7 other curves for 525 efi, 600 - 900 SC curves and a High initial advance curve for Hihg HP N/A motors with idle issues which you pre-set to 24 Deg BTDC and run a 10 Deg curve for 34 Deg total. The HI-6M is a great box and IMO, far more robust and reliable than the MSD unit, with the addition of the built in curves just makes it better all round, it also has a built in rev limiter, adjustable to 100 rpm. It's compatible with the TBIV system, I know Fastlane40 runs two boxes on his Skater Race boat with TBIV distributors for reliability!

I've got some testing to do once I've fitted the new breathers; I'm going to try the new carb settings and try the 5 blade prop again (less pitch). I'm also going to try the LH Bravo 1 24P I just received and see if running left rotation improves handling at all.

I'll let you know how that goes!