Yes, I changed to 22P Bravo 1 props when I switched engines. They should turn fine once I get to spin up the engines.

I have also had several recommendations concerning the secondary opening on the new carbs I am looking at. It seems mechanical secondaries are simpler but less efficient, but more widely used than vacuum secondaries. The vacuum are also significantly cheaper than mechanical. I'm sure there are tons of opinions about the merits of each. Does anyone use the Holley 750 vacuum's and are happy with them? Any opinions on efficiency?

I'm looking to cruise this boat, not race, or even concern myself with very much wide open running. I'm leaning towards 750's or 800's with mechanical secondaries for simplicity.

I have to agree with RumRunner on the intakes. I think you'll be happy with the mid range performance, and good bottom end the dual planes will give you. The dual plane/750 combo should give you some snappy throttle response.

Mechanical Secondary Carburetors are going to be easier to dial in. You may also want to make sure you get carburetors with electric chokes to aid in starting.

Ive run vacuums for years and they took years to set up right, but, this summer I tried mech secondarys I dont like the way they behave compared to the properly setup vacuums. They dont have the "punch" the vacuums did. Thats not surprising. Top end is the same. Fuel mileage pretty much the same too which surprised me, I thought the mech would be worse for some reason. Ill be on a dyno this winter so I will check their behavior side by side. My primary concern is the transition between primary and secondary opening, a typically lean point.

Today I tried a different power valve (5.0) since I started seeing 10 - 10.5 vac numbers at idle. I figured it could not hurt to try. I also dropped jets in the primary's 2 sizes as well. Idles great, but no power under load.....black transom on the left side only. When I accelerate slowly, the engine comes up to 2500 - 2600 and when I put the power to the right engine, the right one will pull the left one up to 2700 - 2800 or so once on plane and trimmed out. If I try to add power beyond that I can hear a slight "dieseling" and immediately pull it back to the previous setting to get rid of that. It seems the carb is so rich when I try to add more power it can't pull any higher, and floods the plugs which I'm thinking is what I am hearing. Timing is the same on both engines and that dieseling sound followed the carb from one engine to the other as well when I switched carbs. Pull it back to idle and it works great. There is some slight hesitation on both engines accelerating through 1400 rpm or so but it clears out above that. I think that could be another symptom of being over carbed and over intaked. The right engine will accelerate to about 4200 rpm and I figure that is because the left engine is no longer helping to push the boat after 2600 or so.

I called Barry Grant tech this morning and tried a few things they reccommended, like changing the butterfly idle setting, lowering the float level to the lowest setting, re-jetting, changing power valves, but they also suggested advancing my timing to 16 degrees base which would top me at about 36 - 38 degrees total advance. Way too high in my opinion so I did not try that.

I think it is time to try different carbs. I am going to try a used 800 0-9022 tomorrow that the local performance boat shop is letting me try before I buy new ones from them. I hate to give up and buy others, but I think I have reasonably tried almost everything except swoping the metering blocks. I have one good carb on my steering engine and really don't want to screw myself into a tow if I can't steer my way in. At least they are letting me take a test drive on the 800 to be sure before I spend the money. I still want to figure out what is wrong with the BG carb since I would like to sell them and don't want to pawn off my problem on someone else. (even though I'll sell them for auto use.) What are all the things that could cause the carb to be extremely rich?

over jetting (77 front / 83 rear now)
blown power valve or oversized power valve (new again today)
cold operating temperatures (water temp 140 - 150 degrees)
high float level (I'm between the lowest and middle setting)
high fuel pressure (I'm at 7 lbs)
4 corner screws rich, (only 1/4 to 1/2 out on all)
retarded timing (I'm at 11-12 degrees base and 32-34 degrees total)

what am I missing? Maybe I will have to take that chance and switch primary and then secondary metering blocks and see what happens. I just really hate to screw with a good running carb, but I guess that is the last thing to rule out. Maybe I'll try that tomorrow when I have that nice 800 sitting there that I can strap on if I need to after that test.

This mystery has been baffling the local best as well. I'm thinking it might remain a mystery as I am about to give up on these old carbs.

Sorry for the continued lengthy posts, but I want to be as clear as I can be about the things I am experiencing with this problem. Thank you all again for your continued interest and advice in this mystery.

Todd

With all the work you've done by now I'm sure you have inspected the internal seals and gaskets of the carb for any internal leak that could bypass fuel into the motor?


Sorry, Just re-read your post where you regasketed.

The only gasket I did not change was the one between the base plate and the throttle body. I did not have a gasket for that, and did not take it appart. I did'nt think there was much there to check anyway. Should that have come appart as well?

Don't know. Was just thinking out loud. I've only worked on Holleys and quadrajets.

I think I'm also going to try the full rebuild kit. I have been replacing parts in kind of a scattered way, but everything has looked good. I guess I should just replace every single gasket, o-ring, seal etc just to make sure. Who knows, this carb may not work great on this big heavy boat, but could work perfectly on a car engine (thinking towards selling them)

I was thinking about just buying another Speed Demon 850 for now and only spending another $400 instead of $800. Will 50 CFM make that much difference between the Holley 800's I'm looking at and another Demon 850? Does anyone know where I can get J-tubes to marineize the auto carbs I have installed? I have not been able to find them. I suppose I could make them to fit the vent tubes if I can't find them. ( I was specing the differences in the Speed Demon 850's and the Speed Marine Demon 850's and they are nearly identical except for the J tubes and nearly 200 bucks each.) I feel like after having them appart so many times now I know the Barry Grant product pretty well (in an amature kind of way), and feel comfortable with servicing it.

I too would like to find some j tubes. But anyway, I suppose if you could get an 850 to run okay on that engine, might be ok for a season. Just watch the rich condition because it could do lots of damage to the plugs, cylinder walls, and if the fuel contaminates the oil, bearings, etc can be damaged. Let us know how the holley works. You'' ll probaly see about 4600-4800 on the good engine once the other one picks up rpm. Then you might have to tweak the props to get you around 5000-5200.