4 barrel surging and wonbt idle below

"1988 305 with 4 barrel.
Star

"1988 305 with 4 barrel.
Starts like a dream, but won't idle below say 800-900 RPM. At that RPM the motor surges to say 1200 RPM and then back. Very constant surging. Above 1200 RPM (only did it once) it sounds great with lots of power.
I am running with fresh gas from a portable can with fresh fuel, fuel line, filter and separator. The carburator inlet filter has also been replaced.
As some of you may know, this boat/engine have not been running for about 3 years.
I am very certain that the carb needs to be rebuilt as it is probably full of deposits and crap. Sounds to me like the needle valve is sticking and or the jets are clogged.

The new fuel filter is clear and I can see that it is not always full. Does that mean the fuel pump is toast?
But when I tested the fuel pump for volume it filled the container in no time flat????

Any input would be greatly appreciated.
James Taylor out"

"James:

You may not have to

"James:

You may not have to rebuild the carb. Dump a can of SEA FOAM in the portable fuel can and run the engine for 15-30 minutes. Let it sit overnight for the SEA FOAM to work on the gum and varnish and run it the next day the same way and let it sit overnight again.

Also dump a half can into the oil so it can clean the varnish and sludge from the engine bearings, lifters, valves and guides and rings. The SEA FOAM will evaporate from the hot oil as it does its job. Dump the rest of the half can in the oil the second day after running it awhile and then run it another minute or two to distribute the SEA FOAM inside the engine. Change the oil and filter after the third engine run to dump out the crap contained in the hot oil."

"Guy,

Thanks for your time.

"Guy,

Thanks for your time.
I did forget to mention that when I did first try to start it, I did put some some carb cleaner/degummer in the portable fuel can.
This fresh fuel and cleaner has been sitting in the carb fuel bowl for about 2.5 weeks.
I don't think we have this SEAFOAM you speak about in Canada.
Any suggestions? A carb kit is only about $20.00.
James Taylor out"

"Did you look under the dist.

"Did you look under the dist. cap? Is the optic sensor all rusted? I changed mine and it ran better. Cap and rotor look good? Plugs in good condition? All ok, then I guess it's time for a carb rebuild. Get a float for it unless the one in it is copper--rare bird though. Take your time and use the manual carb specs. Carb kits are not that reliable for correct specs. Good luck."

"Guy,
The cap, wires and roto

"Guy,
The cap, wires and rotor look great. That being said the rotor will not lift up and off its shaft. Hummmmm!!!
No special tricks are there? The plugs are new.
I guess the writing is on the wall........
R-E-B-U-I-L-D
James out"

"The rotor is loctited on and

"The rotor is loctited on and probably the shaft is also rusted. Mine was. Grab it with a channel lock pliers and twist and pull upward. Still stuck? Crack it with a chisel to get it off. What did the optic sensor look like; sorry, you need to get the rotor off to see it clearly. Use a digital camera and take pictures as you disassemble the carb."

"Your carb secondaries might n

"Your carb secondaries might not be closing fully. That creates a huge vacuum leak that kills idle, but runs great abovew that speed. Check the linkage to ensure the butterflies are closing tightly.

Jeff"

"Me again,
Well it is rebuilt

"Me again,
Well it is rebuilt. Just need to find time to try it. Maybe tomorrow.
F-Jeff,
They were in fact fully closed.
Guy,
It was FULL of crap. I am totally surprised that it even started let alone run.
Where should the air mixture screws be set before I start it and how do I adjust them once it is running?
I know I read it in one of the posts, but it is being hard to locate.

Thanks to both Guy and Jeff for your advice.
I will keep you abreast (I love that word) of how I make out.

James Taylor out"

Per manual specs:

You can p

Per manual specs:

You can perform these settings with a garden hose but then take it to the lake and reset the idle in gear while tied securley to the dock--Jeff's idea.
Turn both in until they just begin to feel snug then back them out 2-3 turns to start.
Get the engine up to operating temp.
Set idle RPM in (CAUTION) gear is 650-700 RPMs.
Set timing to 8 deg. BTDC
Set mixture for each screw by SLOWLY backing one screw out until it stumbles. STOP and remember the stumble point. SLOWLY turn the screw inward while counting the turns of the screw past smooth idle until it stumbles again. STOP and back screw out 1/2 the number of turns from 1st stumble point. Repeat with other mixture screw.

You may have to fine tune mixture on the lake.

"Guy and F-Jeff,

Not sure i

"Guy and F-Jeff,

Not sure if it was good luck or good management, but when I went to start it it rolled over about 3 times, sprung to life and purred like a kitten.
It sounded GOOD.
When I opened the carb to rebuild it, there was so much crap in the bowl that I am surprised that even started let alone run.
I am surprised how easy a Q-Jet is to work on.
I know I will have to fine tune the idle and the air fuel mixture screw when it is in the water.
But that I belive is a great start.
Thanks for all your help and advice.
I will keep you abreast of how it goes.
Sea(lake)trails on Friday.
James Taylor out"