When I tried going to the second step up in richness (8%) I also increased the pump shot AND tried the heavier springs (all of them). With no change. The plugs didn't change AT ALL during any of the changes....A fuel blockage or vaccum leak is starting to make sense. Can you see the "screens by looking into the carb or do you have to remove the carb to check this. Also what/where is the anti-syphon valve and what is it's purpose? What can I do to help rule out a vac leak?

BH:

Lots of good info here.
1. Vac leak can be around intake where it meets head. Spray with some starting fluid, just a quick shot. If you have a leak it will pick up rpm and or stumble a bit.
Hook a vac gauge up and observe it. A leak will make the needle bounce a bit.
2. Screens, don't now but you should pull that carb apart and inspect everything. Find a buddy with the same carb and set it up the same and re-test.
3. Your fuel pressure at running rpm should rule out the anti-siphon valve but they can stick an be erratic. It is located at the tank pickup. Looks just like a regular hose barb fitting but has a stainless ball and spring inside that serves as a check valve. It's purpose it to prevent fuel from leaking unchecked in the event of an accident or fuel line cut. Way I figure your pretty much screwed at that point anyway.
4. Winter grade fuels have different additive packages and it is really hard to get any color on the plugs. I cannot tell you much more than that, perhaps someone with more knowledge on fuel can add to this. I just know that in previous springs when jetting carbs winter fuels did not leave any color.
5. NGK plugs are easier to see color on because of the location and type of porcelain.

Good luck, I suspect you have a gummed up carb or delivery problem.

Tim T.

YOU HAVE TO TAKE THE TOP OF THE CARB OFF TO GET TO THE SREENS.ONCE YOU HAVE THE CARB TOP OFF REMOVE THE FLOAT AND NEEDLE THEN YOU CAN REMOVE THE SEAT. THE SREEN IS ATACHED TO THE SEAT.YOU GET PRETTY QUICK AT THIS IF YOU HAVE DONE MUCH MAIN JETT SWAPPING ON THESE CARBS.I LOVE IT ON A 105 DEGREE DAY.

Went and got the carb of the boat today. I brought the carb home and am planning on checking it over....What things should I look for and where...I figure I will spray it real good with carb cleaner and try and blow the passages out real good with some compressed air....I will keep you all posted and let you know if I spot anything. By the way what are the floats supposed to be set at anyone know?

Thanks
BH

BAD-HABIT
I feel your pain!!!!!!!
I had the same exact problem!
My troubleshooting consisted of the same steps.
Ended up swapping carbs from left to right and the problem followed.
While tearing down the carb for a total overhaul, (less than 1 season of running) I noticed that the bottom of the left bowl had "gold" flakes. Upon further inspection I noticed about 1/3 of the threads for the intermediate jet were missing.
I knew I hadn't stripped them out! I noticed the threads were extra deep on the "good" side of the hole.
I felt that during the MFG. process the hole had been drilled in step 1 and the tapping was done in step 2, but not aligned with the hole drilled in step 1.
I sent the carb back to Edelbrock and they sent me a "reman" carb as a replacement at no cost to me.
I just ran the boat this weakend and the backfiring in the carb is not there anymore.
But I havent been able to "tune" it yet-but- it's a whole lot better now.
I bought the carb about 1 1/2 yrs ago. So if yours is that vintage it might have been a production flaw that didn't get caught.
If all else fails contact Edelbrock. They did me right

Opie...I went through the carb and cleaned it up. Didn't really notice anything real off. The float drop was off alot but I guess that probally wasn't my problem. The float level was off about 2/16" I fixed that but Edelbrock dosen't think the amount would cause a problem to my extent. I orderd some Hi-Flow needle and seats just to make sure the bowls where filling as fast as the bowls needed them. They should come in today. I guess Im back looking at a vaccum leak or a fuel delivery problem..This is the problem child.......God it's hard to love your kids sometimes!
358/350hp roller

BH

bh, check supply line from tank to f/w separator and from there to fuel pump. any split or crack could be causing a supply problem. don't forget the simple stuff. you may have checked this already.

DID YOU CHECK THE SCREENS WHEN THE CARB WAS APPART.ALSO DO THE FUEL PRESSURE CHECK AT THE CARB FUEL INLET.YOU WILL NEED TO JERRY RIG A T-FITTING AND A GAUGE.I USED A HOSE TO THE GAUGE SEEING AS IT IS ONLY A TEMPOARY TEST SETUP AND THIS GIVES A BIT MORE FLEXABILITY.GET A FRIEND TO DRIVE WHILE YOU WATCH THE GAUGE.BE CARFUL NOT TO LOOSE YOUR SUN LOUNGE IN THE WIND.DOING THIS TEST RULES OUT FUEL DELIVERY PROBLEM!!!

Primary metering rods and springs are the power valves in this carb. Your set up should not change in the carb.
The float drop controls how much the needle valve can open, therefore how fast the fuel can come into the bowl.
All your problem sounds like a delivery problem. The fuel pressure check at the carb is where I would start.
Good Luck!!

Since my miss seems to happen at cruise am I understanding correctly that this is the point where the engine is pulling the most vaccum? If this is so wouldn't this lend itself to the miss being a vaccum leak since the engine would pull in the most air and in turn give me my miss condition at cruise? I hope to give it a run on Sunday I will let everyone know a.s.a.p

Thanks for the tips keep them coming....

BH