engine cutting out about 3000 rpm's

[ccruser1]

Greetings,
Had a problem yesterday after running about 30 minutes at 3000 rpm's in calm seas. Boat ran fine then started to sputter and die out. Befor it stalled I pulled back the throttle to idle then slowly increased for a few minutes. I then increased it back to about 3000 and after a few minutes the same thing happened. made it back to slip doing this about 3 times. Runs great at idle all the time. Suspect water in gas as boat was not registered for two years and tank was full. Will add fuel treatment and top off tank (now about 3/4 full, and change fuel filter. Anything else I should look for ?

[oneradride]

Blocked tank vent, after running for a while you are creating a vacuum in the tank and the fuel pump can't overcome it. Just my guess....

[ss3964spd]

Read this post CC, especially #22. http://www.maxumownersclub.com/forum...High-RPM/page3

Dan

[ccruser1]

thanks for your input; I'll check it out.

[ccruser1]

Thanks to those who offered help here. I checked the vent tube and all seems clear. I have added some additives to remove water and refresh the gasoline in hopes that this will cure the problem. We'll see . I am down to about 1/2 tank (25-30 gallons) remaining in tank so I'm not sure if I want to try and just burn it or dilute it with fresh fuel. Any thoughts on this?

[shrew]

Originally Posted by ccruser1

I am down to about 1/2 tank (25-30 gallons) remaining in tank so I'm not sure if I want to try and just burn it or dilute it with fresh fuel. Any thoughts on this?

This is sort of a toss-up. It's late in the season and the fuel is not going to get better with age. I prefer to leave the tank full to reduce condensation, but folks seem to be split on this theory regarding leaving the tank full or empty. I wouldn't expect bad gas to cause a situation where the boat starts, idles and runs strong up to 3,000 RPM, then dies completely. I would expect it to run poorly, however. That is not what it sounds like though. If the gas has sat for two years, I would consider getting rid of it.

Is this a carb or fuel injected motor? What year is the motor?

[ss3964spd]

I gotta say that at this point I soooo don't think it's bad gas. If at all possible I'd remove the vent tube from where it connects to the top of the fuel tank, remove the fuel fill cap, and use compressed air to blow through the vent line from the tank side to the fill side.

Regardless, a very quick way to find out if it is vent related is to run the boat and when the symptom appears immediately loosen the gas cap - if at all possible when the engine starts gasping. Or, while the gas level is low, loosen the cap a turn or two and use a piece of tape across it so that it doesn't loosen further - then go run the boat.

Dan

[ccruser1]

this is a carb on a 4.3 v6. I was able to remove the vent tube and blow easily thru it. Air could be heard escaping thru the vent cover so I know it is clear. It starts right up and runs well for first half hour then it cut out and was run back to slip thru channel at low speed. Was able to put in nuetral and shift into reverse for docking into slip without engine cutting out. Have not checked electrical yet but not thinking this is where problem lies. Any thoughts?

[oneradride]

What year? It's got to be fuel or spark...... I'll still bet fuel but your there and I'm not.
Depending on year... you may have a bad ECM or coil..... I had a coil once that would get hotter than.... you know, and start cutting out, especially at higher RPM's.
Normally, in my experience anyway, ECM's just quit and you get nothing as far as spark.

[ccruser1]

this is a 93 so it has a coil. I still think it is fuel related because of the fact that even after it is hot it runs well at lower rpm's.

[ss3964spd]

Are you saying it always runs fine for the first 30 minutes or so, then starts having problems? Is this a symptom you can reproduce?

If it is fuel (opposed to fuel system) related I really don't think it would run fine for a while then start running bad.

[TonyA]

My 10cents worth;
If you think it’s a fuel related problem and there is no blockage found as far as the vent goes!! Then maybe, since water is heaver than fuel and will sits at the bottom of everything. the first place is will sit after the fuel tank is the bottom of your fuel filter and if it gets sucked further up it will sit in the bottom of your carbie, if only a tiny bit of water is in your carbie it will start to block your jets /change the fuel mixture /restrict fuel flow /stop fuel flow etc etc. I would remove the fuel filter and pore the contents into a container and see what you have after it settles. If you have water in there you should see the separation line of the 2 elements - fuel on top and water below. if on water is there fit the filter back on ( if it is still good ) and keep looking ,but if fuel is there in the filter you need to remove the water out of the fuel lines and carbie and ditch the filter . I have fitted clear water separator to the filter
(A different type of filter with the separation bowl below the filter complete with a drain tap) .this way if any water is in the system it can be drained out from the bottom of the bowl before it gets into the carbie

Just my 10 cent worth Tony

[shrew]

I'm starting to lean towards carb. issues. Since this is a 93, the fuel lines made then are not rated for ethenol. Ethenol is known to break down the inner lining of the fuel lines and clog the lines as well as the carb. The behavior you're describing could be a fuel starvation issue. The same could be said for a clogged fuel jet. As the throttle is increased one of two things 'could' be occurring.

1) clogged fuel line restricts fuel delivery to the float bowl. The fuel burn rate could be higher than the fuel line can deliver fuel, essentially starving the carb for fuel and creating a lean condition.

2) The main jets could be partially clogged. Fuel deliver to the carb body is restricted. As the throttle is advanced, this also causes a fuel starvation issue and a lean running condition.

Either condition could potentially cause the behavior you're describing. You could put in a new set of plugs, or at least one new plug, then run teh engine until the engine stalls. Pull the plug and look at it to determine if you are running too lean.

Since the fuel is so old, there is a chance the carb simply needs to be completely cleaned and rebuilt. This is not a difficult process. Again, I'd be inclined to check the fuel line as well as the fuel pickup in the tank to make sure that isn't partially blocked either. Just a couple of thoughts.

[rscotta]

If you have a timing light, you might check timing after the engine is warmed up and you start to see the problem. There is an electonic unit in the distributor that takes care of spark advance. On my 3.0 spark advances from 12 to 14 deg BTDC at 3000 RPM. If you have an engine manual, the timing curves will be in there.

[ccruser1]

In reply to several inputs let me say that first of all I really appreciate everyones thoughts on my issue. I just bought this boat and this cutting out occured on the 3rd time out after about a 30 minute ride. The first two trips out were about 30 minutes each in rough seas. There was no cutting out on the first 2 trips. That being said, it is hard to say how long this has been happening. I am only assuming that the fuel was two years old as the reg sticker expired two years ago.

I did remove the fuel/water filter and poured contents into clear bowl. No water was seen after allowing to settle overnight. I replaced the filter and added some gas additive to rejunvinate the fuel and added some dry gas.


I took a quick look for loose or missing vacume hoses and did notice that there was no hose to the distributor. Is the distributor supposed to have a vacume hose attached to change the timing at higher rpms?

If there is not supposed to be a hose there I will next look at the carb as I think that is where I will find my problem.

[ss3964spd]

We're all happy to help CC.

Regarding the vac line to the distributor - is there a vacume advance canister on the side of the distributor housing? Probably not.

IMHO, I believe you are chasing a carb problem that doesn't exist. The symptom you described, if it were carb related, could only - in my mind, be caused by a serious blockage in the carb. But if that were the case the symptom would not be intermittent. In other words, it wouldn't run fine (blockage free) for 30 minutes and then die, then run again, then die, etc. Now, if you are saying that the engine has not run since you last outting perhaps the carb is full junk to the point that it won't....forgive me for this, pass any gas. I find this unlikely, too, because the filter should have prevented all that junk from reaching the carb. One quick check is to remove the flame arrestor, open the choke, and look into the carb while operating the throttle. If you see two streams of gas shooting from the accelerator pump discharge nozzels then the carb has gas in it.

Another thing you could try is to rig a temporary fuel tank and see if it'll run on that. Note that the fuel/water filter you mentioned is probably a fuel/water separator (not actually a filter). There will be an actual filter somewhere.

At this point, if the engine simply will not start, you might also want to verify you have spark to the plugs. As was mentioned above, I think there is a electronic module inside the distributor that is known for intermittent issues - especially after it gets hot, and for out right failure.

Dan

[shrew]

I think I missed the part about "it was running fine the first few outings and now it's not".

[pascavone]

water goes to the bottom, and the gas rides on top. the fuel tube in the tank is an inch off the bottom.

so, level ride draws gas, speed and your sloshing water and drawing it into the engine.

You may also have water in the carborator float chamber or simply a sticking float or needle pin seat.

I was thinking fuel pump, but they are not intermittent.

temp gas tank or clean the whole tank out....

[ccruser1]

Thank you everyone for your input. After adding some star tron additive and dry gas then letting the boat sit for two weeks (weather and time available issues) I topped off tank with about 10 gallons fresh fuel and took it out for a test ride. Two trips out each with about 1 hr. running time at high rpm's I had no issues. If this sounds like a paid advertisement forget it.

Again, thanks for everyones input.

[ss3964spd]

and thanks for the follow up!