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454 - 350 stalling

G

gardnersf

Member
Hi, I have 1985 454's. 350 HP. One of my engines beganstalling and had difficulty starting last fall. I'm now trying to get the issueresolved. Basically, the engine will start and run roughly. I believe it isfuel starvation. If I try to throttle, it may rev up but often times it juststalls. I can hear a lot of air hissing through the carb air intake ports. Isthat normal if it is fuel starved? Steps I have taken. 1.
1. Changed Spin on fuel water separator.
2. Sight tube on fuel pump is empty.
3. Pulled the inlet to the carb and turned theengine over. Had good fuel flow – I do not think it is the pump
4. Pulled the carb filter – It was nasty.Changed it out still have the problem.
5. Pulled the carb filter again. Seems to havemore crud.
Bottom line I think I have some crud in the fuel that is cloggingcarb filter. Not sure if that is the only problem though. When I try tothrottle up, I get louder hissing through the carb. Any ideas anything else to check?

Port engine is running fine but does have a separate fueltank and no crossover
Hi, I have 1985 454's. 350 HP. One of my engines began stalling and had difficulty starting last fall. I'm now trying to get the issue resolved. Basically, the engine will start and run roughly. I believe it is fuel starvation. If I try to throttle, it may rev up but often times it just stalls. I can hear a lot of air hissing through the carb air intake ports. Is that normal if it is fuel starved? Steps I have taken. 1.

  1. Changed Spin on fuel water separator.
  2. Sight tube on fuel pump is empty.
  3. Pulled the inlet to the carb and turned the engine over. Had good fuel flow – I do not think it is the pump
  4. Pulled the carb filter – It was nasty. Changed it out still have the problem.
  5. Pulled the carb filter again. Seems to have more crud.
Bottom line I think I have some crud in the fuel that is clogging carb filter. Not sure if that is the only problem though. When I try to throttle up, I get louder hissing through the carb. Any ideas anything else to check?

Port engine is running fine but does have a separate fuel tank and no crossover
Hi, I have 1985 454's. 350 HP. One of my engines beganstalling and had difficulty starting last fall. I'm now trying to get the issueresolved. Basically, the engine will start and run roughly. I believe it isfuel starvation. If I try to throttle, it may rev up but often times it juststalls. I can hear a lot of air hissing through the carb air intake ports. Isthat normal if it is fuel starved? Steps I have taken. 1.
1. Changed Spin on fuel water separator.
2. Sight tube on fuel pump is empty.
3. Pulled the inlet to the carb and turned theengine over. Had good fuel flow – I do not think it is the pump
4. Pulled the carb filter – It was nasty.Changed it out still have the problem.
5. Pulled the carb filter again. Seems to havemore crud.
Bottom line I think I have some crud in the fuel that is cloggingcarb filter. Not sure if that is the only problem though. When I try tothrottle up, I get louder hissing through the carb. Any ideas anything else to check?

Port engine is running fine but does have a separate fueltank and no crossover
 
3x=I got it. Sounds like you could be hearing an air leak in your intake manifold. Since that air does not go though the carb you could be fooled into thinking you have a fuel problem. If you are not sure where the hissing sound is coming from use the old "rubber hose to the ear" trick and poke it around until you locate the source.

CaboJohn
 
Thanks John, I will try again. I'm pretty sure the hissing is coming through the carb itself, like it's drawing a lot of air in past the choke plates. If I open the choke plate more, it stalls . I wasn't sure if a fuel starvation condition will result in that sort of sound
 
OK, Update:
Compression Check:
1: 142
3: 130
5: 130
7: 135
2: 130
4: 127
6: 122
8: 135
A little gap between high and low but right and no stuck valves. About 980 hours on the engine.
I switched carbs but it was too late to run. I will try in the morning. Other fuel filter looks pristine after 1 year so I really think it may be the gas in the starboard tank.
It was definitely pulling air through the carb barrels. If I feathered the choke plate closed it ran a little better.
 
If you want to find your air leak squirt some carb cleaner around the intake manifold and the carb body while engine is cool and running. listen for changes in idles when it high idles you will find your leak, also check vacuum lines and make sure they are not cracked, split, or fallen off. I would also try putting a in line fuel filter in clear sight until you the fuel system cleaned up. Its easier to change the in lines than the ones in the carb.
 
Scott,

See if you can snug up the 4 carb mounting nuts a bit. Not too much, the QJet baseplates can get warped. Your anti-siphon valve is a prime suspect if you are you seeing a lot of crud in the fliters. I went through the same thing and added EZ Flow pre filters before my Racors. It took a whole season before my Stb tank issues cleared up.

I only had to pull the anti-siphon out once though.

Bob
 
Do you still have the original cartridge filters?

Assuming your spin on filters are upstream of the carb, they should be catching the crud that is winding up in the carb's inlet filter...those are rather coarse and if you have crud in them, it is like to be in the float bowl as well. This is reinforced by what I think you described as having to richen the mixture via the choke plate.

You should also check the choke pulloff and its little vacuum hose...that port is also the quickest way to connect a vacuum gauge which is where I'd go next...

When was the last time a tuneup was done???

does the exhaust have any fuel odor (rich) to it?
 
I have the spin on filters, not the cartridge filter. I use 10 micron normally but I wonder if I accidentally got 25 micron filters last time. I did a tuneup 2 years ago and replaced the distributor with electronic, coil and wires. I just replaced the spark plugs when I did the compression check. I am going to get new spin n filters before I run it again.
 
Update:

I changed the spin on filter and I switched
the carbs. The engine ran for a few seconds and then started doing the same
thing. I can keep in running if I pump the gas on and off. I think it's the
accelerator pump on the carb jetting extra fuel. I sprayed carb cleaner around
the intake manifold without much effect, a shot in the throat of the carb and it
picks right up. The carb inlet filter was gumming up again. The carb filter
cleaned right up with some carb cleaner and air. The crud seems a little jelly
like and I think it is just gumming up the carb filter, causing
starvation.

I've started changing the risers and elbows because they are
due so I won't be able to test again for a little bit. Is there any way to clean
the fuel in the fuel tank? I probably have about 30-40 gallons in a 125 gallon
tank
 
The old fuel is likely to be breaking down, chemically, and it would be best to remove it...many have had success posting ads on craigslist and having somebody come and remove it...the gelling could be the byproduct of ethanol and water...

You might want to try an outboard tank temporarily plumbed in to verify the bad fuel hypothesis...

working the throttle will activate the accelerator pump...this is one indication that the idle passages in the carb are restricted and need to be cleaned, too.
 
there is no way that bad fuel....of any kind.....can cause the "hissing" sound that he is describing. if it was bad fuel, he could overcome the problem by spraying carb cleaner directly into the carb as he opens the throttle...even with bad fuel....it will rev. bad fuel will not cause a hissing sound. he has a vacuum leak.
 
I switched carbs and had much the same behavior. When I sprayed carb cleaner in the throat the engine smoothed out and revved up (Throttle was not at full idle) I confirmed the air was being pulled in the carb entry and not anywhere else I could find
 
By the way. I'm doing the risers and elbows just because I was planning on doing them anyway and have the other engine done. I don't think they have anything to do with the problem I am having but I need my garage back and need to get the parts out of there :)
 
that confirms you have a vacuum leak.....just not at the carburetor. it could be a intake gasket, incorrect carb gasket, etc, manifold fitting.
 
As I said in #2 and Cranky has said several times, it still is likely to be a vacuum leak. Several days ago you said you would check the other engine to see if the same hissing sound was there. Was it?? If the sound was not exactly the same, then it is definitely a vacuum leak and you can find it if you just look and listen. The fact that the engine may have other issues does not matter since these engines always have something else wrong. That is part of the fun of boating. If you decide it is a vacuum leak, and you can't find it from the top, and since the heads were off, it is likely one of the gaskets got cockeyed between the head and the intake manifold, and maybe you are pulling air from the lifter gallery. Look at that gasket line carefully and see if everything looks lined up. Did it get torqued correctly? Is there any debris caught in the seal area?
 
John, Cranky,

I've never had the heads or intake manifold off. I do have a vacuum gauge but have never used it, Can I connect the vacuum gauge to the tube at the carb and tell anything from the reading? When I sprayed carb cleaner in the throat of the carb when it was struglling, it shifted to higher idle and air noise went away (Sounded normal) . I do appreciate all the help as it is very hard to describe what is going on. I want to run the other engine with the carb i switched but have to fix the fuel line first. Too many times on and off and it has a split now.
 
My bad, I got you confused with someone else that had done a head job. But that is good news, as your leak is unlikely to be in some place you can't get to.
 
Hold it! You're on a wild goose chase caused by false assumptions and bad advice--and lots of it.

That "hissing" is normal--every motor does that at certain throttle settings. You're making it into your problem, which it is not.

Your problem is a common one: BAD GAS. The ethanol in the fuel has formed a white crud that goes right through fuel filters to raise holy hell with your engines.

Just went through this myself on launch day. Starboard motor would start, but stall continuously at anything near idle, Had to rev it up, then pump the gas to keep her running in gear. Stall, stall stall..Finally ate through the crud in the carb to hold an idle--for while--before more white gook (see below) came in, then here we go again!

You need to have about 20 % of the gas in the LOWER area of your tanks sucked out and disposed of. Top off with fresh gas--witha stabilizer--then run the the crud out of the carbs and all will be well.

Jeff

PS: I filled the tanks on mine with gas, and added a stabilizer, before winter layup, yet I still had the above problem. God help us all if those morons in Washington D C stick us with 15 % "evil-nol".
 

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....absolutely correct !! lots of BAD ADVICE !! stick to BASIC troubleshooting and ask yourself why would "bad fuel", only cause one engine to hiss....?? we have tried to steer you in the right train of thought of troubleshooting, BUT......it seems all contributors have been graded as simple fools by an "expert".........
 
If one pickup tube in the tank was cut 1/4" longer than the other, guess which one gets the "crud" that accumulates in the bottom of the tank?

Another possibility is the load on the boat induces a slight list lowering the fuel pickup tube on that side...same result.

A bigblock with a correctly set idle speed screw that has a vacuum leak will idle at a high rpm, how much determined by the size of the leak...
 
For what it's worth I have two fuel tanks without cross connects. Port engine runs off a completely separate tank. generator also runs of stbd tank along with stbd engine.

I've had to work a lot the past few days so I haven't gotten back to it. I only have about 30-40 gallones in a 125 gallon tank. \
My boat does list a little to stbd when both tanks have equal fuel and the engine pickup tube is outboard the generator pickup tube. may be something to it.

My plan for now is to chase the gas down. I'm working on getting a connection to a temp tank to help troubleshoot and figure out a way to get some of the existing gas out.
 
Whoa! Family feud! Our late entrant, fastjeff, may be right about the bad advice. But here's the thing. There is always a tendency to believe what the other guy says (i.e. the famous hissing sound). Now the proper way to check if such an observation is even relevant is to compare it to the other engine. That and part swapping are the easy ways to trouble shoot a duel engine setup. It may not work if something outside the engine is bad (as in fuel) but if something is wrong with the engine it sure does work. You were asked for the comparisons and failed to provide. Those of us that went with the vacuum leak hypothesis assumed your hissing observation was meaningful but probably should have given up when we could not get the comparison.



Get your fuel situation straightened away (fun fact: the technical name for that white gunk is snot) and then if you still have a problem with the engine do a serious comparison with the other engine to find the issue. And in answer to the question about the vacuum gauge, by all means check that.....but check both engines and see what that tells you.
CaboJohn
 
Progress!
I finally got some time to work on this.
First off, the port engine would not run with the STBD Carb. Would not start. I put the port Carb back on (I had only run it in the Stbd Engine for 30 seconds to a minute) Port ran fine.
Then I finished my Exhaust elbows and riser job
I took the stbd Carb back off the boat, Sprayed Carb Cleaner in any port I could reach and used some pressurized air and carb cleaner to blow out some of the passages. I know this is not a proper carb cleaning\rebuild, but I wanted to see if I could at least get it to run.
I hooked the Stbd engine to a new outboard tank with fresh gas and some StarTron added. It took a while, but I was able to get the engine started. Once it started, it idled and revved normal. It's still on the hard so I can't do much more with it, but it's good to hear it run again. I did hear the "hissing" sound form the carb, but just as I was throttling up and it quickly stopped as the fuel caught up.
So now, I hve two working engines and still have some bad gas in the tank.
I have been experimenting with the bad gas. I added extra stabilizer\fuel treatment to the 20 gallons I pulled. I mixed it 50/50 in my tractor and weed whacker and they ran better than ever. I've also taken a sample in a jar and added a couple of different treatments to see how it evolves. With Sea Foam only, the gas began to clear up, the white "snot" that was in the gas started to disappear. (There wasn't a lot to begin with.
I added some StarTron today to see what will happen.
So now, I have to figure out what to do with the gas in the tank. I really don't know how much I have as I don't really trust the fuel gauge to be all that accurate. I'm guessing I still have 20-30 gallons in a 125 gallon tank.
 
I just wanted to close the loop on this as several people helped me.
The problem was definitely fuel. Once the boat hit the water, I filled the tanks up with fresh gas. STBD took only 60 gallons to fill which meant I had 60 gallons of bad gas mixed with 60 gallons of good. I added about 12 OZ of StarTron to the tank as well on top of the 16 oz I had added earlier
On the first test run, the carb filter clogged after 5 minutes of running at 3000 RPM. I motored back at 1500 RPM and cleaned the filters.
I figured I was set into a mode of lots of filter changed and would try to burn off the gas as quickly as possible.
After thinking about it, I decided to speed up the process. I built a cleaning rig for about $200. The rig consists of a fuel water separator with bowl, an marine fuel pump, A 2 micron screen filter, switch, fuse, alligator clamps and about 25 feet of fuel hose and assorted connectors. I had to add a primer bulb to get fuel to the suction of the fuel pump.
I connected the suction of the rig at the outlet of my existing spin on water separator and set the discharge to the fuel tank fill.
I ran the pump for about 4 hours. I estimate that moved about 120 gal of fuel through the rig. It was a very interesting result.
First, the fuel was slightly cloudy and had a few flakes. It was also a dark amber color, sort of like dark olive oil.
After 4 hours, it was very clear and looked pretty much like light vegetable oil. a mild yellowish color.
I ran the boat after reconnecting everything, changing the on board spin on filter and carb filter (I flushed the fuel line that wasn't used as well)and went for a ride.
the boat ran much better. STBD ran to about 3800 RPM, which is a little off peak, and port was about 4200 which is fine. I ran at 3400 RPM for about 30 minutes before it started to bog. I moored up, checked the carb filter and I ha da little bit of gunk plus a little piece of Teflon tape that must have been on one of the fittings (I used thread sealant but PO had Teflon tape.

Ran the boat for another 30 minutes without any incident at 3500 RPM and hit 3850 or so peak.

Today I took the boat out again. Ran it for a solid hour at 3000-3400 RPM with no issues.
.
The fuel was very cloudy but not discolored. I ran the rig for about an hour on a 5 gallon jug. After running it the fuel was much cleaner but not near as nice as the fuel on the boat.
Now the fuel on the boat was mixed 50/50 with valve Tec gas and ha da ton of StarTron in it.
I'm going to add some StarTron and try again. Basically, I think the StarTron really works wonders. From what I have read, it bonds the impurities allowing them to get filtered out.
So now I have a functional boat again. I will run this tank down low and refill with fresh again. I also plan on running the cleaning rig on the other tank just for good measure.
 
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