Stalling Problem AQ125B

[Maityme]

I have a Bayliner Tropy hardtop with a VP AQ125B. The boat likes to stall upon acceleration.
The engine runs great on the trailer with outdrive in gear or not no mater how long you run it. The boat runs fine in the water at first. You leave the dock accelerate and run on plane for about 30 - 40 minutes than you idle and as soon as you try to accelerate, the engine falls flat on its face. Once you play with the throttle for a little bit, than you can get the boat back on plane again. I am at witts end with this problem and need some suggestions on which way to turn.

Here is what I have on my boat:
AQ125B with single barrle solex carb
The entire fuel system has been replaced including gas tank. (aluminum tank starting leaking at a weld)
Carburetors have been rebuilt (I have 2 carbs, one that I rebuilt and one that a professional carb shop rebuilt -does not matter which carb, both do the same)
Distributor removed and cleaned and converted to Pertronix Electronic Iginiton
fuel filter has been replaced twice.
fuel pump has been replaced.

I have advance the timing and retarded the timing and it seems to run best with advance timing, but still stalls. (I do not know if the mark I am using is correct because the mark was painted on white by somebody else. I do not see any other mark, nor any notches in the pulley or harmonic balancer)

A fisherman that wants to fish for the stripped bass
R/
Maityme

 

[sqbtr]

Re: Stalling Problem AQ125B

The 125b only had one carb. Post a pic of what you have. Accelerator pumps are a common cause, also make sure the shot lands directly on the venturi support it helps atomize the fuel. The carbs must also be syncronized perfectly.

I'm thinking someone may have tried to upgrade your 125 with 151 carbs.

 

[Don S]

Re: Stalling Problem AQ125B

Have you checked the timing with a timing light? Is it to specs at book rpm? Did you check the advance timing?
Have you actually adjusted the idle mixture with the engine warmed up and at idle rpm? Not just going by the initial setting, that's only a starting point.
When was the last full tuneup? Compression OK?

The 125b only had one carb.
I'm thinking someone may have tried to upgrade your 125 with 151 carbs.

Sounds to me like he has 2 different carbs for his engine, not that both are used at the same time.

 

[dennis461]

Re: Stalling Problem AQ125B

He only has one carb on the boat.
He owns two carbs (as I read it).
" (I have 2 carbs, one that I rebuilt and one that a professional carb shop rebuilt -does not matter which carb, both do the same)"

My guess, without being there, they both have a fuel delivery problem or float level problem.
Here is what I know about 44PA1 1-bbl on a 2300CC volvo in a 20' boat.
If the float bowl is full, (and none of the other stuff works, pump, filter, hose..)you should get one good launch and up to plane before the fuel runs out with a warm engine.

So the symptom sounds like running out of fuel.
A pressure check of the line at the carb could be done.
Trickier would be checking the float level in the carb while on the water :facepalm:

 

[Maityme]

Re: Stalling Problem AQ125B

I only have one carb installed. I bought a second one and had that rebuilt as well. No matter what carb I use, it does the same thing. I am picking up the other carb from the carburetor rebuild shop tomorrow with a second rebuild of this carb.

 

[Maityme]

Re: Stalling Problem AQ125B

Yes Don, I have went through this boat with a fine tooth comb did everthing by the book as well by my instinct of being a mechanic for 18 years. Full tune up and the works have been done to the engine. Compression on are cylinders are good and within a +-5 psifrom each other. That is why I am totally stumped on this one, And it only happens after the boat has been running for a while. If compression was an issue, than it would do it worse when the engine is cold, but it does it once the engine has run for 30 minutes or so when compression would be at its best because of expansion? you don't think compression could change that much towear I loss compression when it is hot?
My mind is open for all possibilties.

Now here is something that I did not think about. The first 3 times that I took it out this season after I finished all the work, I had no problems at all. Boat and engine worked like a champ, than on the 4th trip the stalling began and I have been fighting it all summer trying this and that, and now I am out of things to try. The carb shop has once again rebuilt my other carb and I will be trying that one out soon. Please work!!!

 

[Maityme]

Re: Stalling Problem AQ125B

I would love to figure out how I could monitor float level while out to sea.

 

[sqbtr]

Re: Stalling Problem AQ125B

Have you checked the tank vent, pick up and anti siphon valve?

 

[Maityme]

Re: Stalling Problem AQ125B

Not yet, but I will.

 

[sqbtr]

Re: Stalling Problem AQ125B

Sorry about my reading comprehension on your original post, I think the time change messed me up!!!!

 

[orbanp]

Re: Stalling Problem AQ125B

I would love to figure out how I could monitor float level while out to sea.

I did that on an outboard motor. The float bowl had a plug under the regular fuel level. I attached a drilled screw there that I attached a transparent flexible hose on the outside, tilted upwards. That showed the same fuel level as inside the bowl. It was a great diagnostic tool!
If you do that, think about safety, think about spilling fuel!
You also might want to check out the fuel pump.

Good luck, Peter

 

[Mullin]

Re: Stalling Problem AQ125B

I had this exact same problem, as do many people with that aq125.

Try adjusting the screw on the accelerator pump rod so that the pump squirts near instantly when you hit the throttle. Any hesitation and the motor dies before the extra squirt of gas is delivered.

With the idle and air screws adjusted and the timing set right, the accelerator pump is the last adjustment needed. Worked for me.

 

[Maityme]

Re: Stalling Problem AQ125B

Well, I am finally back in town from business, now i have time to figure this thing out. did you tighten the nut or loosen? Is there any literature on this adjustment?

Thanks
Maityme

 

[Mullin]

Re: Stalling Problem AQ125B

I had to loosen the nut to get the accelerator pump to engage sooner.

My best suggestion would be to start it and warm it up. Pull the carb cover and disconnect the throttle linkage at the carb. That way you can manually hit the gas at the carb without the shifter locking you back into N every time or needing a helper to hit the gas.
Just hit the gas and see how long it takes for the fuel to spit from the 'candy cane' looking port. Adjust the nut and try again, and again until it's not stalling when you hit the gas from idle.

 

[Maityme]

Re: Stalling Problem AQ125B

Will give that a shot if needed. I got the boat back together by installing a new Volvo Fuel Pump, had the carb shop go through carb again and replaced the fuel filter. Its winter time here and the weather is poor. I will give the boat another shot as soon as I get favorable winds. Striper season is far from over.

I did notice one thing though, advancing the timing improved the boat 100%.

 

[sqbtr]

Re: Stalling Problem AQ125B

I did notice one thing though, advancing the timing improved the boat 100%.

Check the timing belt.