Overheating + Fuel starvation issue?

[theredboat]

Hi everyone! Been a while since i've been here as my a4 was running great for the past two years (many thanks to all the help I received here).

Over the weekend, I went on a 2 day cruise. Engine was running flawlessly for the first day, motored about 4 hours. Day two I motored for another 4 hours before looking down and seeing the temp gauge at 200. Brought the throttle down and the engine stalled, not immediately, but like it was fuel starved... sputter then die.

After letting the engine cool, I attempted to restart many times, at best I'd get some sputtering, but not a full start. Had to get towed in.

The fuel issue sounded carb-related so I pulled the carb and sure enough it was all gobbed up in the main jet. I cleaned it thoroughly and tried to start. It started almost instantly! But as I brought the trottle back, the sputtering and revving started again, even though now I could keep it running by increasing the trottle. by the way - I could hear the RPMs reving up and down without any throttle adjustment on my part. What does this mean?. On top of this the engine began overheating again, resting at about 200. This was in neutral, so very little load. Very normal amount of water coming out the back.

Is it possible the overheating and the sputtering are related? Was it just a coincidence these two issues began at the same moment?? Any thoughts would be appreciated.

[hanleyclifford]

A lean mixture and overheating can be related. I think the problem is not the carb but something upstream like (hate to say it) the fuel tank.

[CalebD]

It has been called "hunting"

When the engine revs up and down on it's own your culprit is likely dirty fuel. Been there done that, wrote the movie script.
A few vinegar soaks of your cooling jacket may help keep the engine temps lower. If that doesn't work try the more harsh Acid flush procedure outlined in a sticky somewhere here.
Photo is of what came out of the bottom of my fuel tank when I finally pumped it out.

[Mo]

Revving up and down can also be a sign of water. Check your separator while you are at it. Have a look at your timing as well. FWC or RWC?

[theredboat]

When the engine revs up and down on it's own your culprit is likely dirty fuel. Been there done that, wrote the movie script.
A few vinegar soaks of your cooling jacket may help keep the engine temps lower. If that doesn't work try the more harsh Acid flush procedure outlined in a sticky somewhere here.
Photo is of what came out of the bottom of my fuel tank when I finally pumped it out.

WOW! Yeah, I somehow doubt these tanks have ever been cleaned. What is the process for tank cleaning? Can I simply pump it out by hand? Seem like a potentially messy job (I have a half full tank at the moment).

Yes, I will try the vinegar / acid route as well. As I said, I have a feeling the two issues are separate. It just seems hard to believe they occurred at the exact same moment.

[theredboat]

Revving up and down can also be a sign of water. Check your separator while you are at it. Have a look at your timing as well. FWC or RWC?

The water thing also sounds reasonable. But the engine ran just fine for 4 hrs before starting to rev up and down. I don't know much about separators. Is it the kind of thing that can become full over time and then stop functioning?

I considered timing. I've never adjusted it, but I'll take a look at the manual and see how it's done.

thanks a lot!

[sastanley]

trb, if you have a squeezy bulb in the system for priming, you can pump the fuel out of the tank that way..it is not a quick process, but it would work. When my tank ruptured (well, really it developed a pin hole leak), we emptied it that way. It probably took an hour, but that was 15+ gallons. This will also give you a chance to analyze a sample of the fuel to see if it is contaminated. Let's hope it is not looking like Caleb's.

[Mo]

I have a few quick ideas but I have to run...so I'll make it brief.
-check impeller to ensure a piece didn't cause a restriction
-if OK...remove T-stat and see how it runs with it not in there...I don't use a t-stat on my RWC engine...only by-pass valve left 1/2 open
-change filters and take carb apart and clean it.

Will catch up later.

[theredboat]

I have a few quick ideas but I have to run...so I'll make it brief.
-check impeller to ensure a piece didn't cause a restriction
-if OK...remove T-stat and see how it runs with it not in there...I don't use a t-stat on my RWC engine...only by-pass valve left 1/2 open
-change filters and take carb apart and clean it.

Will catch up later.

Thanks Mo! Wont get to the boat until the weekend but in the meantime..

- I have doubts it's an impeller issue, but it's easy enough to check. I'm seeing full water flow out the back of the exaust. I'm very familier with blocked water as I've seen it many times, but this doesn't seem like the case.

- I cleaned the carb, and it helped the starting issue, but still getting the revving issue. I will check the filters as well.

thanks!

[edwardc]

If you have an electronic fuel pump, it can be used to pump the bulk of the volume out of the tank.

Just temporarily plumb a long fuel line from the pump output into a jug or container. Jumper the OPSS, disconnect the coil, and turn on the key. This will minimize the the amount of hand-pumping to get out that last bit of crud and water-laden stuff that is below the pickup.

[CalebD]

WOW! Yeah, I somehow doubt these tanks have ever been cleaned. What is the process for tank cleaning? Can I simply pump it out by hand? Seem like a potentially messy job (I have a half full tank at the moment).

Yes, I will try the vinegar / acid route as well. As I said, I have a feeling the two issues are separate. It just seems hard to believe they occurred at the exact same moment.

I didn't know when my tanks had last been drained either but my engine started doing the "hunting" thing with it's revs and it got so bad it would stall out intermittently.
I finally pumped out the tank by hand using a siphon mate pump (@ $40) into Jerry cans but the last bit looked just like my picture. No small wonder my engine was complaining.
Use whatever means you consider to be safe to pump gasoline out of your tank into containers. If you let the containers settle the water and crud will fall to the bottom as it did in my picture.
Any time my engine starts revving erratically I suspect crap in the fuel tank being the cause.
You may think that your tank's fuel pick up tube is at the bottom but ours was not; it was about at half tank level. That left a lot of room for crud to build up at the bottom of the tank.