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Stalling

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wismo

Regular Contributor
So I have a Mercury Force 90 horsepower had a bunch of work done to it over the winter runs great then suddenly stalls started back up can only get a quarter of the speed back out of it and I smell gas had the carburetors cleaned what else would it be the person that I bought the motor from said that it had a problem with flooding
 
I think cylinder 3 has low compression than the others could that be the reason the guy I had bought it from said it flooded if it sit for little while it will start back up and be normal again could that be the choke circuit that's bad or the lower compression in the 3rd cylinder
 
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What year?
The fuel pump is operated off #2
The older style choke shouldn't be a problem.
The newer primer style has a diaphragm that can go bad and allow extra fuel into the system.
If you have that system?? Try pinching off the hose from the enricher and see if that stops the flood??

What's the compression on all 3???
 
Year is 1993
Last year did compression check.i think 1 and 2 were around 110 and 3 was in high 90s
When i did gasketsi noted 3 cylinder had some scoring.
Motor ran great up on plane then a dead stop.
Then finally running on plane again
But to.me bogging
 
I haven't had a chance to take the boat out of the water but I did the mechanical check on that valve and it seems fine
 
What test on the primer?

You have the blue or black Prestolite ignition system?
Or the Mercury system?
It came with both types??Pics?

Usually the coils don't heatup like a car coil.
In all my time(30+years)I've only seen 1 maybe 2 coils go bad.
Try switching the coils.
Usually weak or no spark is a stator??

Check stator and trigger resistance, trigger wire sets read approximately 50 ohms between the wire sets (DVA-5V or more), stator reads 680-800 ohms, DVA 180V or more from blue to yellow.
2.If readings are good, disconnect kill wire from one pack. If the dead cylinder starts firing, the problem is likely the blocking diode in the other pack.
You need a DVA meter or the attachment for an analog meter.

Get a different gauge and redo the comp test.
You removing all the plugs to do the test?
Your results should be 145-150 not 90
 
Press button on primer and airflows through not pressing no air flow through it
Seems ok thats from the shop manual.

Compression test with plugs out I will get ahold of another tester
 
Start the motor and pull the primer hose off.
Should be no fuel coming from hose.

While running pull hose off and hit choke/primer and see how much fuel comes out.
 
close enough usualy within 10% of other cylinders is acceptable, move on to spark test,Have you tryed a cylinder drop test to find weak cylinder.pull spark plugs wires 1 at a time with plastic pliers note rpm drop on each cylinder,biggest drop weakest cylinder.Low spark or not enough fuel in cylinder.
 
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Compression looks fair.
That a Harbor Freight tester?

Usually the comp is 145 to 150.
But if all 3 are close it should be ok.
I'd keep an eye on #1 just in case??

Try a decarb and see if the comp goes up on #1
Use Mercury's Power Tune or OMC's Engine Tuner.
They say Seafoam is a good decarb, NOT

But the comp shouldn't cause the problem of stalling.

Test the ignition system, then fuel delivery.
 
Tester from advance auto.its new
Just a recap since I purchased this boat I replaced new
Rectifier
Stator
Due to a no spark condition.
Plugs
Fixed and or clean wiring on the mercury style ignition box I take picture of it later.
Cleaned carbs.
Did not check float height didnt think of it
As I mentioned the owner before me had this exact problem

 
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Also looking at that picture if you look closely at the screws for on the carburetor air fuel mix two of them have the slot pointing one way and the top one the screw points a different way I don't know if that's just a coincidence or as Jerry pointed out the problem with cylinder one
Could cylinder 1 be running rich and somebody tried to lean it out
 
Thats what i figured but it does look further out than other maybe a couple turn not sure buti wont mess with it.
I still need to testthe fuel primer also
 
Where's the pics of the carbs??
Pics I see are the same.

In the pics I can see a possible problem: The screw holding the cover on the fuel pump.
Not positive but I don't think it's the right one. Could be sucking air??

When you squeeze the ball does it get hard or just kinda hard?

You do the tests I suggested on the primer?

Check the tank vent line and the pickup in the tank?
Any inline connectors?
More pics???
 
I did not do the test on the primer yet but I will today I will also post more pictures of the carburetors when I squeeze the ball it get hard to where i cant squeeze it anymore.
 
20141006_181223.jpg
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Oops got a Taunton River sunset mixed in
 
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