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New to me 40ML 6E9 L 358334 misses intermittently

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0rsbbit7

New member
Hello everyone,

I picked up a new to me Mariner, which seemed to be running alright when I got it. It also seemed to run the first little while perfectly as well. Now maybe an hour later it appears to be missing intermittently.

I think it is a 92, from some Google searching, and I was very fortunate to find this forum… I’m wondering what the rough order of troubleshooting should be? Maybe this order:

New gas?
New plugs?
New points (do these even exist anymore)?
New coils?

the engine looks immaculate for something that could be 30 years old
 
Doubt you find any points.----Trouble shooting is what you start with.----You did install a new water pump impeller I hope.-----Then use a timing light to see if it is one or more cylinders with a miss.----Compression test results are ?----Mixing gas and oil at 50:1 on it ?
 
racerone said:
See post #2--Are you mixing gas and oil ?---Replaced water pump impeller ?
Click to expand...

new gas and 50:1 oil makes no change.

I have not changed the impeller. Is there a challenging task? Can parts be generally found?

the pee stream seems strong and appropriate temperature, but admittedly I have not verified at WOT.

To be more precise, the problem only occurs at high or WOT. Once I bring it down to cruise or idle, it will disappear after a brief period of time. It runs properly otherwise
 
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0rsbbit7 said:
new gas and 50:1 oil makes no change.

I have not changed the impeller. Is there a challenging task? Can parts be generally found?

the pee stream seems strong and appropriate temperature, but admittedly I have not verified at WOT.

To be more precise, the problem only occurs at high or WOT. Once I bring it down to cruise or idle, it will disappear after a brief period of time. It runs properly otherwise
Click to expand...

Impeller is easy to do but it wouldn't cause misfire. I need a little more info. So it drove fine for an hour or so, until the engine got warm and then it started to misfire? Does it run fine when the engine is cold in the driveway? Does it rev all the way up in the driveway? is it stopping at a certain RPM and holding steady or does it just sound like its bogging down when you try to go to higher RPM?
 
Gavin27 said:
Impeller is easy to do but it wouldn't cause misfire. I need a little more info. So it drove fine for an hour or so, until the engine got warm and then it started to misfire? Does it run fine when the engine is cold in the driveway? Does it rev all the way up in the driveway? is it stopping at a certain RPM and holding steady or does it just sound like its bogging down when you try to go to higher RPM?
Click to expand...

hi there,

thank you for your response! I should not have said misfire, it feels like that is very incorrect in hindsight. It definitely feels like a fuel issue. It will run perfectly fine so far as I can tell indefinitely at idle, cruise, on a stand, in gear, out of gear, etc. I will accelerate fine as well.

however, if I run it at WOT, for more than say 5 seconds, it runs into problems, but not immediately. It can run at high-throttle for maybe 30 seconds, but the longer it is at WOT, the more significant the issue is. Sometimes to the point of completely slowing down and cutting out, requiring a dozen pulls to get back to a reasonable idle. Once a normal idle has returned, it is happy again for hours on end - so long as you don’t go near WOT, that is.

If I understand how motors work (I don’t, but maybe JUST ENOUGH?), I believe that the threshold of malfunction appears to be just around the position of the end of the timing advance, when the carbs still have more room.

to another poster, it has one coil that feeds both spark plugs
 
Running in gear on a stand is still neutral.---The prop does NOT have to work to move air !----Revving it to full throttle in the driveway is a mistake and means nothing !----Water pump impellers must be changed every 5 years or so.-----Perhaps test run with another tank and hose.----Do you have / can you borrow or rent a timing light ?
 
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Is 106 and 108 compression approximately correct? The gauge I used is… old let’s say, and I could not figure out how to disconnect the lockout to be able to spin open the throttle all the way - if this number is off I’ll give it another whirl.


I was able to source a diaphragm, but not any of the other parts in the fuel system. Can I replace a diaphragm without new gasket? Or is it likely to fail?
 
Hello everyone,

My questions still stand, such as a manual, parts sourcing, etc., but I managed to figure out my particular issue. It was the fuel filter. Thanks for your responses
 
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