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Mercruiser hesitating and backfiring

Z

ZEB

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I have a 1983 4 Winns 22.5 Cubby Cruiser with a Mercruiser 228 engine. I took the boat out for the first time a few weeks back and it ran fine until I was coming in from 15 miles out. I got to within 3 miles from my dock and the engine started to hesitate. I slowed down and gave it some gas and it would still hesitate once in a while backfire thru the Carb. I was able to nurse it back to the Dick going approx 10 MPH, anything more the engine would hesitate and Backfire.

After that, I placed some Gas treatment in the Gas, cleaned the arrestor and filled it up (Approx 1/2 tank low) and took it on a short trip and ran fine.

Well I took it out other Day and went approx 20 miles out and trolled for approx 5 hours and it ran fine. when heading in I was approx 5 miles out from the dock and it started to act up. IT would hesitate and backfire and I was only able to get it up to 7 MPH. Anything higher it would start acting up, hesitate, backfiring or even stalling out.

Well I am hoping that I can get some assistance in trying to Diagnose the problem... Some was telling me a gas filter but I find it hard to believe that is the issue since it ran approx 7 hours with no issues.

Someone also mentioned a Module and I have noticed the RPMS are not as high as they use to be so I am not sure if that is the issue, any assistance is appreciated.
 
i lean towards water in the fuel in these cases first, and the easier to correct, and cheapest. Also can have something to do with hose.

So allow me to explain the hose first, this new gas can and is eating old hose like crazy can even be a flap on the inside of the hose restricting fuel.

Pump all the gunk and junk and water off the bottom of the tank, want to know how i can post a old post i made.

check your filters all of them and the fuel pickup tube. the anti-syphin valve.

run it. still doing it then new hose. run it still doing it carb rebuild .

one thing at a time and run it follow ?

Once the fuel system is clean and new hose and it's still doing it then go after the dist, and or ignition parts.
 
I pumped all the fuel out of my onboard fuel tank when i got it.

You can do one of 2 things, pump the water out of the bottom, or all the fuel out and here is how.

If you just wish to pump just the water out of the bottom of the fuel, you will need to purchase a cheap electric fuel pump from any auto store dc powered.
You will also need about 15 foot of cheap fuel hose from the auto store and clamps to fit the fuel pump.

Install the hose on the fuel pump both ends and cut about five feet on the sucking side of the pump just look for the arrow on the pump.

Remove the fuel pickup tube it's the one where the fuel hose hooks to the tank a 90 degree angel fitting, it's a anti-siphon valve. Unscrew it.

Crank the bow of the boat all the way up, and stick the hose connected to the electric fuel pump 5 feet into the bottom and back of the tank.

Into a clear container pump the water out till you see clean fresh fuel and stop the pump.

Or into a large container pump all the fuel out.

Now check the valve by blowing thru it, check the screen thats its clear.

Install the valve and pickup tube your done.

Question do you have a fuel water separator on the boat, good to have.

Copied and pasted here form another website i used to post to wrote by me
 
Thanks for the info. I noticed you mention a water/fuel separator. I do have one and replace it every year. Do you think with me doing this that water is not an issue... Also, would it act up, stop and act up again. If it is water, wouldn't the seperator caputure the water. Should I plue that off and see if there is water in the separator?
 
I unscrew it and dump the contents in a clear clean container and let sit, if there is water will sep. and you will see it on the bottom.

You also must remember the reply i copied and pasted is to a different question.

But it was closely related to your problem.
 
All, Finally made it to the boat and poured the contents into a clear jar and saw very little water and very little sedement on the bottom of the jar... Also I did look at the filter fiilter on the Carb and it looked clean.

I replaced the Fuel filter and Fuel water seperator along with the Anti Syphon valve. Took it out fishing and it ran well, but then again I did not get below a half a tank, this is when I encountered the problems before. I am planning to take several days off two weeks from now and I will let everyone know how it ran.
 
You could have something in the tank like paper, clogging up the fuel pickup. I have seen all kinds of stuff in tanks, maybe some joker before you threw something in the tank.

Listen could be water on the bottom of the res . of the carb.

Fix is a carb rebuild, clean the filter in the fuel pump. I didn't see you mention that filter.

What psi the fuel pump giving ?

Finally you could try running on a external tank of gas.
 
If it continues to misbehave put a timing light on it while someone drive. See if the timing stays on the money. If it jumps all over the place it may be the plug wires or the timing chain.
 
Thanks for the info, I am planning to get back to the boat in a week and a half and I will check the items mentioned above. I will post my findings... Thanks to all.
 
It appears the problem has been fixed. I replaced the Anti Siphon valve on the Gas Tank and the water separator and the Problem has not occurred the last five times I have been out. My money is on the Anti siphon valve as the cause of the problem. Well anyway, the problem appears to be fixed and hopefully this answer will assist others should they have a similar problem. Thanks to all for their advise in fixing this problem.
 
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