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Have a few questions about my 91 mercury 90hp motor. Wondering if someone with some experience could PM me and help me trouble shoot my problems. I'm getting the motor to  crank and it sounds like its about to turn over then cuts out abruptly.   Thought it could be the battery so I hooked up a portable jump start and got it to fire then shut it off because the motor was out of the water. Issue is this motor is on a shore station so I'm trying to get it to fire on the water. Lowered the boat down to get the lower unit in the water and could not get the motor to crank again. I'm not smelling any gas in or around the motor so it isn't flooding. I've pumped the ball it seems to be getting hard but won't stay hard for very long. I've got a feeling that maybe the kill switch is going and that is why it wont go. I pulled the battery inside and put it on a charge and it said it was good to go. Put it back in the boat, got it to fire once, shut it down because once again the motor was too high. I put a volt meter on the battery and it was showing 12v but I was told it should read 12.8 or something similar. Is this just a battery issue or is there more at play here? I don't want to go replacing fuel lines if the issue is just a battery. Does the kill switch shut off the fuel pump? Pulling the smart plugs are a no go on the water because the motor has a cover over the three spark plugs. I should smell gas even if the plugs are bad right? Sorry for the rant some insight would help.

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If the motor cranks when it's tilted but won't when it's down there's probably an issue with the wiring. It's losing the connection when you tilt the motor down.

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2 minutes ago, Tim Kelly said:

If the motor cranks when it's tilted but won't when it's down there's probably an issue with the wiring. It's losing the connection when you tilt the motor down.

That's a good point I didn't think about checking the connections. I had a bushing for the throttle linkage break and just replaced it. I could have popped something loose removing the cowling. Man I'm going to feel real dumb if its that simple.

6 minutes ago, Tim Kelly said:

If the motor cranks when it's tilted but won't when it's down there's probably an issue with the wiring. It's losing the connection when you tilt the motor down.

It cranks up or down but doesn't turn over I should say. I never fully got it to turn. Ill be sure to check all of the connections. Thanks for the insight.

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15 hours ago, tbone1993 said:

Have a few questions about my 91 mercury 90hp motor. Wondering if someone with some experience could PM me and help me trouble shoot my problems. I'm getting the motor to  crank and it sounds like its about to turn over then cuts out abruptly.   Thought it could be the battery so I hooked up a portable jump start and got it to fire then shut it off because the motor was out of the water. Issue is this motor is on a shore station so I'm trying to get it to fire on the water. Lowered the boat down to get the lower unit in the water and could not get the motor to crank again. I'm not smelling any gas in or around the motor so it isn't flooding. I've pumped the ball it seems to be getting hard but won't stay hard for very long. I've got a feeling that maybe the kill switch is going and that is why it wont go. I pulled the battery inside and put it on a charge and it said it was good to go. Put it back in the boat, got it to fire once, shut it down because once again the motor was too high. I put a volt meter on the battery and it was showing 12v but I was told it should read 12.8 or something similar. Is this just a battery issue or is there more at play here? I don't want to go replacing fuel lines if the issue is just a battery. Does the kill switch shut off the fuel pump? Pulling the smart plugs are a no go on the water because the motor has a cover over the three spark plugs. I should smell gas even if the plugs are bad right? Sorry for the rant some insight would help.

I had a similar issue with my motor in that I could get it to turn over sometimes but not all the time. The ball on mine wouldn't get hard and stay that way either.  I ended up replacing the ball and the fuel lines on the motor.  Now its only about 1/2 a squeeze and the ball gets hard and the motor starts up every time.  If the ball won't get hard then the fuel you are trying to push to the motor is going somewhere else or the ball itself is leaking.

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First off, a 12V battery is considered an almost "dead" battery at 12VDC, that's about 80% discharged. 

Second, a battery that has been left sitting for more 24 hours at a charge level below 80%, 20% discharged starts to sulfate, so if that battery has been sitting for very long at 12VDC, it's probably junk.  Connect a voltmeter across the terminals and try cranking it, if the volt meter drops below 10.8VDC, the battery has lost enough cranking amp capacity that it's junk. 

 

Also, lets make sure were are talking apples to apples.  Cranking means the starter is spinning the motor over.  Starting means the motor is running or trying to run.   If it's not cranking, that means the starter is not spinning the motor.  If it's not starting, that means the starter is spinning the motor but it will not run.

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Take off the cowl (engine hood) and look at the carbs, if it's a carburator type engine.

Your 90' era Merc should have electric fuel pump activated by pushing in the start key and you should see and hear gasoline spraying and the choke butterfly closing. 

When you turn over the engine and it starts you will know it's running and smoky when running on it's own power.

Get yourself a pair of hose ears if you can't put the engine in water and run water through the engine before starting, make sure the engine is in nuetral. 

If your engine isn't running on it's own go buy a new marine cranking battery to eliminate the battery question.

Let us know how things are going.

Tom

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What plugs are you running? 

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