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Aq125a problem

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cjk1

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"I have a 1983 Bayliner Explor

"I have a 1983 Bayliner Explorer with this engine and am having some trouble. After the engine is good and warm it starts surging and will die unless I pump the throttle and slow down, and if I idle for a few minutes I can give it gas and it will get to 4000 rpm or so then start sputtering out again. Until today it would idle just fine, but now that is starting to be unsteady as well. I've checked the compression and all 4 cylinders are within 3-4 pounds of 175. It has the electronic ign. conversion. The boat sat for quite a while with 1/2 tank of gas which I have drained and replaced, also replaced the fuel filter. I'm thinking I'll replace the fuel pump and rebuild the carb. Also the exhaust bellows has a small hole, I'm going to replace that as well. Am I missing anything really obvious?"
 
"First, I think you should che

"First, I think you should check that the idle mixture is what is supposed to be and that the flame arrestor is clean. Also, you may want to check that your fuel tank vent is clear. If the vent is plugged, you will get vacuum inside the tank and the engine will starve when the pump becomes unable to suck fuel.

Also, don't be surprised if the ignition coil is becoming faulty or one of the wires is loose or a wire connector is rusted.


The small hole in the lower part of the exhaust bellows is supposed to be there to drain water from the exhaust when you pull the boat out ofthe water."
 
"Thanks El Pescador. Would the

"Thanks El Pescador. Would the idle mixture affect the high speed performance, or should I check that only because of the uneven idle today? I took off the carb and found some gunk in there. Yesterday we had the boat out and I was able to watch the fuel going into the carb as we accelerated. It looked great for a few seconds, then just sort of fizzled out. I'll check out the coil, but I know the one in there is almost new. Does it matter how that drain hole is oriented on the bellows? The hole I'm seeing is on about the second ridge and it's on the top. It seems like its on upside down and backwards."
 
"The idle mixture should not a

"The idle mixture should not affect the high speed performance, but it makes a big difference for idling.

The drain hole must be at the bottom of the exhaust bellows. Also, make sure that, if there is a flapper installed in the bellows, is not installed backwards!!!

Another thing to check is that the fuel pump diaphragm is not perforated. There should be a clear plastic tube going from the pump to the side of the carburettor, and there should be no gas in it. If you see gas, the fuel pump diaphraghm is perforated and unmetered fuel will be reaching the carb, which could cause the engine to stall."
 
"It is sometimes better to use

"It is sometimes better to use exhaust bellow without flaps, but then You have to install the later version of flaps at the exhaust outlet on the drive. You eliminate the risk that the flaps getting loose and blocks the exhaust passage in the drive, and even obtain substancial noise reduction."
 
"My drive has the flap on the

"My drive has the flap on the exhaust outlet. I'll install the bellows correctly and check to make sure there is no flapper in there. There isn't any fuel in the clear plastic tube, but if the pump is just getting old would that cause those symptoms? Thanks again for the info on the bellows."
 
"The fuel pump is often blamed

"The fuel pump is often blamed for all sort of engine troubles, but the problem is usually elsewhere. You may want to stick a pressure gauge in the pump discharge (a cheap vacuum-pressure gauge with a neoprene hose utilized in automotive applications to check vacuum in the intake manifold and fuel pump pressure will do), then crank the engine and if you get 2.5 to 4 psi then the pump is OK."
 
"I just got a boat with the 12

"I just got a boat with the 125A engine...I expect to have several similar problems since it has been sitting for a few years. I concur with the possible vaccum leak or vent clogged. Another possibility is that there's trash in the system, could be in the tank or bowl of the carb(not sure what kind of carbs these things have) which gets sucked up and clogs the system...or just not enoug fuel getting in to keep the bowl full..as it runs out the engine chugs down...similar to cracked fuel line sucking air. I've got a pile of old boats doing the same thing and have to just tinker with each one till I find the problem."
 
BTW... I've yet to get an

BTW... I've yet to get an old one with a bad fuel pump...maybe dirty but not bad....and I've had over 50 old boats of all flavors... almost always its in the fuel system...dirt or bad hoses...lots of gummy crap from sitting...or rust/trash...dirt dauber's nests in old tanks..etc.
 
"Well, after rebuilding the ca

"Well, after rebuilding the carb, replacing the fuel pump, messing with the alternator, replacing plugs and wires, replacing the coil, draining and cleaning the gas tank, I finally got the pickup tube out of the tank and it had wads of junk in it. I tried to blow through it and could barely get any air through. I cleaned it all out and the boat runs great. I'm sure I would have done all those other things eventually, but none of them was the real problem."
 
"Glad you got it running by th

"Glad you got it running by the beginning of the boating season.
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