2004-50HP Keeps Clogging Up Carburetors

[yzerepzz]

Not sure where to start with this engine.......

Engine is a 2004 F50TLRC

I bought the boat from a friend that had it sitting with old and probably ethanol based fuel for about 4 years or so. After doing some basic maintenance on the engine and getting it ready for the water again i take it out and it would not want to go past 2400rpm. It would just bog down. I noticed it was cyl. #2 not working at that rpm.

I disassembled and cleaned out all the carburetors but that did not fix the problem.
I went thru the carburetors a second time and on #2 carburetor I noticed i had to stick a soft cleaning rod thru the main jet to unclog it and be the same size as the other jets. Went back out for a test run and it ran almost perfect at 5500rpm more or less.

After using the engine once more after this it ran fine for a couple of runs then it went back to the same similar problem as before but this time it was on carburetor #4 and it had a white almost rock stuck right on the main jet. Cleaned it out once more. And this time i added and external fuel tank and installed a second filter inline. Also changed out the water/separator and small filter in the engine. And blew out the fuel lines. Basically everything in the fuel system is new.

Went back out again and this time it ran really good and smooth all morning. No issues. But almost before leaving and after a short WOT run i started noticing it was running a bit rough on low speed. Right around 2200rpm but it runs good at higher speed past this. So this is to the point im at now. And now its on cyl. #2. Looks like the low speed passages now got clogged up.

Why does it keep clogging up like this? Even after running on a new clean tank with clean fuel? Can the metal of the carburetors be falling after itself inside. ???

Sorry about the long post. If anyone has any suggestions please share. Thanks.

[99yam40]

what did the inside of the carbs look like?
are they corroded or nice and smooth and clean.

could there be stuff hiding in the fuel pump or lines that hits the carbs after cleaning?

ethanol is not the best fuel to be using if you can avoid it
and never leave a motor sit for long periods of time without draining everything of fuel

[TownsendsFJR1300]

I would be suspicious of where you got the fuel from first off..

Second, as crap was found after other tear downs, invest in a "sonic" cleaner (or borrow one)… With the crap already found in the carbs, there's likely more hidden. The sonic cleaner will clear that out...

The carb material (aluminum) wouldn't be causing the issue...

You may want to check the primer bulb and actually spray brake cleaner thru the fuel lines (not just air) and see if brown crap comes out. Non marine fuel lines are known to have the inside break down and come apart (but that's likely not your issue)…



A mower carb varnished up and then the same carb cleaned in a sonic cleaner with dish soap and water ONLY:

[yzerepzz]

The inside of the carbs did not look clean and smooth. They were dirty with white buildup/corrosion. Fuel pump and basically the entire fuel system is new, except the water separator housing. I’ve been using REC90 fuel with Star-tron fuel additive. I even installed a second modest sized filter after the separator to catch any more crap that may want to flow thru there.

I’ll take a look at possibly getting the carbs on a sonic cleaner and blowing out the lines again with some cleaner. The primer bulb is new also.

One thing that came to mind is when i unclogged carb. #4 that one time i didn’t check any other carburetors because i didn’t have time. And i had been running the engine of the internal tank still. Im suspecting that tank may be dirty and had flowed clogging crap up to the carburetors before i changed to the external tank. I’ve heard of ethanol breaking up and making those plastic tanks fall apart inside? But why did the engine run good for a good part of the day and then start to clog up again on low speed?

[DennisG01]

You mentioned that the entire fuel system is basically new... but you didn't replace the fuel lines. Ethanol won't damage the plastic fuel tanks in any way - but it can deteriorate the inside of the fuel lines - plus there could be crap still inside the lines. Just blowing them out with a cleaner doesn't mean they're clean. Cleaner's aren't magic - you may only have "softened" gunk in there allowing it then to travel to the engine. What about the fuel lines on the engine, itself?

The number of filters you have isn't as important as the filter's specs. What are the micron ratings of them?

I'd continue cleaning/replacing fuel lines and keep running the portable tank, for now. See if you can get to a point where you've eliminated the issue.

[yzerepzz]

I did replace the fuel lines. All of them and also all the small ones behind the carbs. I would have to take a good look inside that fuel tank to see how it looks. Its pretty darn tight in there though. Barely any space. I don’t want to have to take off the console and floor again to take it out.

To be honest i don’t know the micron size of the filters as i was just in a rush to get this engine running right and bought the first one i saw at West Marine. I may look online and get a better one depending on what the engine does. What size do you recommend? The water separator is a 20 micron.

[DennisG01]

OK. You had mentioned that you "blew out the fuel lines", which is why I didn't think you had replaced them.

10 micron is kind of the industry standard for most water/fuel separators. But you can get (commonly available, anyways) 2 micron filtration, as well. Check out Parker (makes Racor).

But for now, I'd keep using the portable tank. That way you know for sure you are getting clean fuel (assuming the portable tank is clean, of course). This will eliminate the built-in tank as a variable.

However, a buildup inside a plastic tank (assuming no foreign material got into the tank) is going to typically be from old/varnished fuel. Ethanol fuel will then start to break up the varnish. But that is a brownish color, not whitish. A whitish color can come from fuel sitting inside aluminum (the VST tank on fuel injected models, for example) tanks. Possibly the same can happen in a carb bowl. But they're relatively easy to clean.

[yzerepzz]

Thanks for your input. I’ll check out that fuel filter.

[99yam40]

I do not see how anything got past all of those filters to plug up the carb passages/jets, so I would be looking at the carbs themselves.

if the fuel bowls/and bodies are pitted/corroded, it seems that that is where the stuff is coming from that plugs things up

[DennisG01]

I agree - 20 micron is still quite small and certainly doesn't sound like what he's seeing... especially since the fuel line and tank side of things is essentially new. It's just good to know what size filter we're dealing with.

Keep running the portable tank, but check those carbs/jets out real well to make sure they're intact. For cleaning... you will probably have to go "deeper" into cleaning them than you have been.

[yzerepzz]

I’ll see how it runs this weekend and depending what it does i may disassemble all the carburetors again and put them on an ultrasonic cleaner.

[zenoahphobic]

I think most has been covered. Ethanol not only eats rubbers and plastics, but can loosen and move varnish etc. that was "inert" on non ethanol fuel.

You seemed have gotten rid of a large amount of this gunk, your bigger main jets not causing much problems but your idle circuit has got gunk.

Carby's have got passages that are hard to get clean, good soaking in cleaner (no plastics left on carby though) and a good ultrasonic clean is the way to go these days.

Amazing how engines can run well for a long time, and all of a sudden don't because of something tiny in the fuel.

[yzerepzz]

Yes thats true. And it gets very annoying and bothersome when these problems keep coming up and you just want to be able to go out on the water and have a good time.