Engine Stalling

[HarryB]

My atomic4 starts right up and runs fine until I try to accelerate. If you try to throttle up (in Nuetral) the engine just dies. You can nurse it up slowly and it will sputter a little and then finally accelerate.

Engine will also stall nine out of ten times when it is put into gear (forward or reverse) regardless of throttle position. When it doesn't stall, the engine RPM drops to nearly a stall and then picks back up.

Finally, boat speed under power is down from where it was in the spring (but this could be from summer bottom fouling)

[luvmyi36]

Harry,

Your symptoms sound like what I went through at the beginning of summer. I would guess that you are having a fuel flow problem. Start at the tank, and check that you have flow all the way to the carb, checking filters and connections along the path. If you have flow to there, (this is where my problem was), take the carb off, get a big pan to keep all parts in and do the cleaning, and take the carb apart cleaning parts as you go. Make sure you get all the jets, float, etc... Mine was really gummed up badly, and as soon as I put it all back together, it fired right up and ran better than ever. I have put approximately 60 hours on since then with no problems. Hope this helps.

[HarryB]

Thanks.... but I have replaced all gas lines, installed new gas/water separator filter, rebuilt carb, rebuilt fuel pump, even bought and tried new portable gas tank in case it was a fuel or fuel tank issue.

All to no avail.

[marthur]

Possibly your exhaust?

When I had your symptoms, it was dirt or grit in the carb.

Some others have posted, though, and they have reported very similar symptoms. The cause was a partially blocked exhaust.

I would check the whole system because I am nuts. But it would definitely pay to check for a build up of scale at the point water is injected into your hot section. Another place to look is the flexible rubber exhaust tubing, which has occassionally become seperated. The inner part would collapse and block the exhaust.

In the mean time, keep those sails handy!

Mike

[jayw]

When the engine begins to stall, does closing the choke help? If so, one possibility is that the carb passages are blocked or that the adjustments for the jets are off.

[HarryB]

Timing

Thanks...I'll try the choke this weekend.

Does the distributor on the A4 mechanically advance the timing when the engine accelerates? If so, could the hesitation and lack of power be due a problem with the distributor?

[baileyem]

Hesitation and poor acceleration

Harry
It sounds as though you may have one of 3 problems: poorly adjusted carbureator jets; poorly adjusted timing (yes the timing does self advance under accelleration if your distributer is working properly); an obstruction in the exhaust system. I will not go into the details of how to check and correct each one as they have all been thouroughly disscussed in this forum, and you can easily get the details on each situation with a little searching. They will be done up in a lot more detail and elloquence than I can manage, too.

Good luck

Mike

[Bob.Griffin]

HarryB, your symptoms sound very similar to mine this summer, engine hesitating when the throttle is increased and sometimes cutting out, uneven running in idle, reduced power when motoring, etc. I , too, checked everything and replaced fuel lines, filter, cleaned the carb, checked the exhaust, etc, etc. Then I read another thread on the forum to do with vapour locks and fuel vapour coming out of the gas due to summer temperatures. I followed Don's advice, installed a primer bulb to pump out any vapour in the fuel lines and now have a smooth running engine. A quick test to see if you have the same or similar problem is to pull out the choke when your engine is idling erratically, if it runs smoother and slightly faster, you have a fuel starvation problem which could be due to vapour/air in your fuel lines. As Don pointed out, the electric fuel pump cavitates easily if you have vapour or air in your lines. Just a thought.

Bob, c/o Saga, Ontario

[HarryB]

Got down to the boat today and it accellerated without hesitation with the choke fully engaged. Also, I was able to put it in gear without the engine dying. So it appears that it is not getting fuel. As I mentioned earlier, I have rebuilt the carb. (newer model with fixed main jet) and fuel pump and installed a manual priming bulb in the fuel line. Since the problem resolves with the choke engaged the problem seems to be the fuel is not being sucked into the engine. I assume there are two reasons for this...a restriction in the fuel supply or an air leak that is causing a lack of vacuum in the carb. bowl.

Any suggestions on what to do next to nail down the problem?

Thanks to all for your help so far.

[jhwelch]

I had my engine die due to an odd problem -- the intake pipe in the
fuel tank had apparently sucked up something that caused a blockage.
I used compressed air to clear it and eventually got around to draining
the tank. Perhaps you could try something similar to see if there is a
blockage vs. an air leak.

-jonathan