briggs opposed twin major carb trouble

my brother just acquired, for free, a big Murray tractor with an 18.5 opposed twin, and peerless 820 transaxle the engine seems to run good, as long as we trickle gas into it, because the carb is trashed, the fuel tank had an open gas cap and it was stored out side through the winter, so the tank was half full of water, unfortunately it also got into the carb, the fuel pump and float bowl where full of trash and nasty slimy goo, the float was seized closed and the water in the bowl evaporated, the main problem is i don't think we can even rebuild this carb it's so full of crap, does anyone know of a cheap alternative to the stock carb or have a working carb for an opposed twin they'ed be willing to part with cheap, we're on a very tight budget and can't afford a lot for parts

A carb re-build shouldn't be too expensive, and it might save your carburetor. I'd say as long as the butterflies move freely and without a lot of play, the float doesnt have any holes, and the carb casting isn't damaged it should be savable with a re-build kit. Try soaking it in some carb cleaning solution or even gasoline for a week or so, it just might clean up pretty nice.

Yeah I haven't met a carb yet I couldn't save.  The one guy on here like to boil his carbs in a vinegar and water solution.  Sounds like a good way to save money on carb cleaner.

Like Carl said try that. My fear is it has filled up with the powdery white junk.

@mightyraze not just powdery white junk, there's rust, hard white chunks of something, almost looks like lime scale, and black and brown chunks of something i can't identify, and of course the goo that actually looks and feels like vasoline petroleum jelly, but i'll let him know what you all suggested and let him decide what to do from there, thanks for the advise

Yeah that while limey stuff is hard to clean.

Compressed air can help clean out jets and what not.

he decided to sell or trade off the opposed twin, said he prefers a single cyl or v-twin, i reminded him he had a very good running Kawasaki 22hp v twin on the cub cadet he picked up for $150 or would have if he hadn't already sold it,

Yeah, I'd keep the oppy, they are pretty good engines. Flatheads are easy to work on, easy to mod, and don't have as many moving parts as a v-twin, which makes them more reliable.

he has a good strong running 12hp he's planning to run for now, i don't think it will have much trouble with pulling the murray, he's planning to leave the rear pulley stock for now with just a slightly larger front pulley, and it pulled his big yard machine pretty good, until something in the varydrive started shredding belts, he's had to replace them 4 times in the last 2 months

The 12 hps do pretty good. Those vari drives just shred belts for no aparent reason. 

Rust doesn't matter in a carb, as the major parts except the air mixture screw , are brass or aluminum and clean up very well generally .

Well...rust doesn’t matter if it doesn’t flake off. Go after rust with a wire brush or pick at it with a Flathead screwdriver. If it doesn’t come off from that it won’t come off while the engine is running

I definitely wouldn't just leave rust in the carb.