4.3 mercruiser popping sound

[Rbryan94]

Hi everyone,

I have twin 4.3 alpha one's. I started the starboard engine and it's perfect. The port engine wouldn't start because it had no fuel. I checked the anti-siphon valve and it was loaded with snot. I cleaned it and started the motor. It's popping, not ticking like a lifter does. It was harder to turn over than the starboard engine like when the battery is dying (it's not) The popping sound seems like it's coming from the carb. The carb also is spraying a small amount of gas almost like a valve is stuck. This is the first time I started this year. I fogged the engines last year and changed the water fuel separators. I changed spark plug wires and double checked to make sure they firing order was right. they are 1988's with thunderbolt ignition rebuilt 3 years ago from the marina with 100hours on them. Boat never saw salt until last year. Thank you for reading this and adding input.

 

[Bt Doctur]

Re: 4.3 mercruiser popping sound

Hard to turn over could be a cracked manifold allowing water to enter and the carb spraying back might indicate a stuck valve.
Exactly how did you winterize the motors, dont leave any steps out.

 

[Rbryan94]

Re: 4.3 mercruiser popping sound

I have superflush installed on the boat. These are great when at the dock because I flush the motors without them running everytime I use them. Even better is when I winterize. I bypass T-Stat housing with superflush and pump five gallons of anti-freeze through the motor. I changed the oil, water fuel separators, fogged the engines until the died out. I changed spark plug wires.

 

[MikDee]

Re: 4.3 mercruiser popping sound

Recheck your firing order, Clockwise from the top- 1-6-5-4-3-2

 

[Rbryan94]

Re: 4.3 mercruiser popping sound

rechecked twice today. It's correct

 

[Bt Doctur]

Re: 4.3 mercruiser popping sound

without draining the motors first ,you didnt have the freeze protection by just pumping it in. If you pump the af in first ,how do you run the motor to fog it? Step by step ,please. Trying to decide if you have a cracked manifold or cracked block.
So the steps were: I bypass T-Stat housing with superflush and pump five gallons of anti-freeze through the motor. I changed the oil, water fuel separators, fogged the engines until the died out. I changed spark plug wires.

 

[Rbryan94]

Re: 4.3 mercruiser popping sound

Ok first I warmed the motors and changed oil. Then I ran the motors again with new oil in them and fogged the motors until they died out. Then with the motors off I pumped five gallons of anti-freeze from my transom inlet to the manifolds and engine (I think there are eight lines on each motor and manifold) that flush and protect

 

[Bt Doctur]

Re: 4.3 mercruiser popping sound

If the therm was closed from passing the cold af thru it ,you never got enough of it in the block.
Couple of things you can do to narrow it down. Remove the spark plugs checking for moisture or a very white appearance, that's water intrusion. I`m assuming the boat is still on the hard or trailer so with the muffs on and water flowing ,crank the motor with the plugs out.
Your looking for mist or water droplets to exit a cylinder.
Remove the valve cover and check to see that each rocker arm is moving correctly with none having a lot of play or a loose push rod. that's a stuck valve indication You can also remove the rocker arms and see if all the valve stems are the same height, the stuck one wont.

Your not making any sense with the flushing thing .Isnt that connected to the main water inlet hose? Has nothing to do with the rest of the engine cooling hoses?

 

[Rbryan94]

Re: 4.3 mercruiser popping sound

Thank you for all the time you gave me. I will do what you say. I hope it's not a cracked block. Actually I hope it's not a cracked anything! The superflush system enters both above and below the T-Stat housing ,so that shouldn't be a problem. I have hope because I did my other motor the same way and it's fine. Thanks again and I'll keep my fingers crossed