#3 Cylinder won't draw fuel 90"s 70 VRO

At least that's what the Marina said -I have no understanding of what the mechanic said. I have a fuel problem on the #3 cylinder they said it wasn't drawing in fuel. great spark, great compression not fuel. they said they switched the cards and the same thing. they said it was either a broken piston skirt or a bad crank seal. I am having an extremely hard time believing this. any suggestions?

Great compression and a broken piston skirt..... not likely! What are the compression readings of all cylinders?

With the spark plugs removed, you should have spark at cranking speed that will jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it?

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark.

If the above two areas are as they should be, that does leave a fuel problem. The problem you describe is normally due to a clogged carburetor or a broken or stuck open leaf valve on a reed plate.

With the carburetor throats visible and when you're cranking the engine over or have it running, is a excessive fuel spray being blown out the #3 carburetor throat? (bad reed plate)

Could be a reed valve as well.-------Is this something that developed all of a sudden ?---------Did motor run ok and suddenly lost power?-----Post as much as you can as to what happened and what the symptoms are ?----Nobody here is standing beside your motor to " look / listen / feel it " so you have to post information.

joereeves said:

Great compression and a broken piston skirt..... not likely! What are the compression readings of all cylinders?

With the spark plugs removed, you should have spark at cranking speed that will jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it?

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark.

If the above two areas are as they should be, that does leave a fuel problem. The problem you describe is normally due to a clogged carburetor or a broken or stuck open leaf valve on a reed plate.

With the carburetor throats visible and when you're cranking the engine over or have it running, is a excessive fuel spray being blown out the #3 carburetor throat? (bad reed plate)

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I just got the call from the marina this morning, The boat is at my cabin 2.5 hours away. I am not close to being a mechanic but I have a very good mechincal understanding. The motor was re-built last July and has less than 20 hours on it. Nothing this marina said made any sense which is why I posted. I am picking the boat up tomorrow and running s few simple tests myself (Compression, Fuel, Spark) Not being a boat motor expert is why I started this post. I cannot believe that having compression could also cause broke piston skirt or bad crank seal. So I will post tomorrow the compression, what happens when I pull the spark plug wire off while running and how much gas is in the carb after holding my hand on it. On the other question, it ran great when I put the boat away for the winter, it ran great the first few outings then it started having issues starting, it started very hard. It seemed lie this happened after I lowered the motor from being tilted up. My other concern is last Saturday I had 1000# of people in the boat cruising at about 15mph (it's a pontoon boat) and it really didn't seem to run bad how is that possible running only on 2 cylinders. I will keep you gentleman posted.... Thank you

Yes, it's probably a good idea to get that boat out of that marina. Was it also rebuilt at that marina?

If running the engine on a flushette, have the water turned on full force.

Another thing to do that anyone can do.... Remove the carburetor face plate so that you have access to the carburetor throats

With the engine running, with insulated pliers remove one spark plug wire at a time to observe the engine's reaction which should be a even drop of rpms on all cylinders.

If one cylinder, in your case #3, does not respond... with the engine still running, stick two fingers into the carburetor throat on each carburetor, one throat at a time of course acting as a manual choke.

If the rpms drop, the engine is already being supplied the proper amount of fuel. (Carburetor okay)

If the rpms increase and the engine smooths out (if it was running poorly to begin with), that particular carburetor is faulty. Let us know what you find.

I have the boat home, The owner of the marina was actually quite nice and openly admitted they may have missed something BUT didn't want to throw parts at it. This after he put a new control box on it and suggested I replace all 3 coils because that's what usually takes out the control box. We had terrible weather here Sunday so I didn't get a chance to try any of the tests you suggested. I will hopefully get those done tonight and get the results posted tonight. I appreciate all the advice and suggestions. I figured I would have to put more money into the adventure just not so soon.

dwoeckener said:

I have the boat home, The owner of the marina openly admitted they may have missed something. This after he put a new control box on it and suggested I replace all 3 coils because that's what usually takes out the control box.

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What planet are these people from?

Money

Good Morning. I got home from work and started the tests you suggested. There is plenty of spark, I put a spark tester on cylinder 3 and it flashed fine, in fact there was a blue spark the jumped from the connection to the engine housing. With the motor running I put my hand over carb on cylinder #1, good suction and it choked the motor, same on carb #2, on carb #3 light suction, I could feel it but it didn't choke the engine. When I removed my hand it was covered in gas. I then pulled the plug wire off on cylinder number 3 and nothing happened, no change. My multi meter has a tach built in and I tested all 3 coils and they were all 830RPMs at idel. I then removed the three spark plugs and checked compression. I do not trust the reading of my gage it is quite old, but I was looking for consistency, and they were all three right on. The plugs from #1 & #2 looked oily or maybe fowled from running rich, the plug from #3 was washed with gas

Possibly the bottom crankshaft seal is not in good condition.----Powerhead would have to be removed for inspection.

I've lost track.... If you haven't already removed the reed plate assembly in order to check the reed plates and the associated gaskets, do so.

Post #3 suggests to check the reed valves.----- I would hope that advice was taken at first opportunity.----Inspection and trouble shooting is the path forward.

racerone said:

Post #3 suggests to check the reed valves.----- I would hope that advice was taken at first opportunity.----Inspection and trouble shooting is the path forward.

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Agreed... The reed plate section would be grabbing my attention right now.

In post #2, I asked about excessive fuel being sprayed out the carburetor throat (bad reed), but apparently the engine was in the marina at the time.

I will attack the reeds tonight, with regards to excess fuel, based on the condition of the carb cover and the bottom of the engine, there is gas everywhere, and the fact that when I cover the intake on carb 3 with my hand and when I remove it it is soaked with gas, I would say there is definitely an excess fuel problem with Carb #3