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97 Mercury 75 ELPT Motor that wont Idle / Run right

S

sonyrules

New member
I recently acquired a pontoon boat with e 97 mercury Force 75 Boat motor. The original issue was the motor would not idle. I have done all kinds of things to this motor and it appears it won't even run at all now. Below are all the items I have done and the result.

Motor SN: 0E260622
Model: 1997 75 ELPT

- Changed the plugs: No difference in running
- Removed the carburetor and replaced a few parts, then completely soaked it in Seafood for 48 hours: seemed to run a little smoother, but still would not idle, even with adjustment
- Replaced Fuel tank, fuel line, and fuel filter: No difference
- Tested compression in all cylinders, they were all good (~110)
- Replaced Fuel Pump: It got worse, instead of trying idle, it would start run for one second and then die, it didn't even spit and sputter like it used to.
- Rebuild the old fuel pump: Did the same as the new, made it worse Would start up and die right away.

So of interesting note, When I rebuilt the fuel pump, the old rubber flanges were torn and worn out (both of them), The replacements were solid (no holes as expected). It at least ran a little bit with the torn rubber flanges.

Just before it dies, if I choke it, it will speed back up, and within 2-3 second dies out. I have posted links to 2 video, one of it starting and dying,

http://www.udsgroup.org/application/video/Boat Engine - Stall.mp4

and the other where I choke it to keep it running.

http://www.udsgroup.org/application/video/Boat Motot - Choking.mp4

It sounds like it fuel related, but I just can't pinpoint where the issue may be. I am running out of idea on what could be causing the issue, any help would be greatly appreciated

Thank you!
 
Here are a few thoughts,
Have you replaced the fuel lines?
When you hand pump/prime the fuel system does the bulb stay hard?
If you have a fuel line problem, depending on the order of replacement you may need to clean the carbs again...
When you cleaned the carb did you clean all the jet hole with a fine brass wire?
After cleaning the carb did you start with idle enrchment screw at 1 1/2 turns from soft close?

Your videos didn't work fro me... Is your tank clean?
 
FishingLite, Thank you for your response, Answers to your questions

Have you replaced the fuel lines? Yes, New bulb as well.
When you hand pump/prime the fuel system does the bulb stay hard? It does, Its hard to the point that you cant pump it anymore.
When you cleaned the carb did you clean all the jet hole with a fine brass wire? I did not, is their a video that shows me how to perform that?
After cleaning the carb did you start with idle enrchment screw at 1 1/2 turns from soft close? I am assuming this is the screw on the top, and Yes, I started at both 1, 1.5 and 2
Is your tank clean? YEs, its a brand new tank, with brand new hardware.

I correct the video link are below. Broswer didnt like the spaces.
http://www.udsgroup.org/application/video/motorrunning1.mp4
http://www.udsgroup.org/application/video/motorrunning2.mp4
 
FishenLite, Thank you for the Video, I ordered the tools and will give it a good cleaning this weekend and let you know how that goes.

Thank you again!
 
sonyrules said:
FishenLite, Thank you for the Video, I ordered the tools and will give it a good cleaning this weekend and let you know how that goes.

Thank you again!
Click to expand...
How did you go with the carby cleaning /jets - did you get the motor to run better - I have the same motor.
 
racerone said:
Checked flywheel key ?
Click to expand...
I have had lawnmowers strike objects that killed the engine. Engine wouldn't restart......lots of painstaking trouble shooting and problem was.........kinetic energy in the flywheel kept the flywheel trying to turn when the crankshaft, connected to the blade, was stopped by the impact. The key didn't completely shear.....only partially but that was enough to cause the problems.

When you inspect your key, can be done looking straight down from the top of the flywheel after the flywheel locking nut is removed, the key needs to be totally square....."totally" square.

Damage to that key is usually caused by the engine striking something at a high RPM. Most propellers are either protected with a rubber slip clutch, or the replaceable type with plastic as part of their construction. Hitting objects with the rubber insert reseat themselves if the engine is cut back to idle and N gear then back to where you were. Replaceable hub types usually tear up the plastic rendering the prop useless to produce thrust.....so it might be iffy considering an outboard engine but worth a check since it's not a complicated process to inspect it.
 
racerone said:
Flywheel has to be removed to check the key.----Or put #1 piston to TDC and check timing marks.
Click to expand...
I guess different models are different. On the ones I checked on my engines, what I said is all I had to do. But you are apparently in the business and I'm not so I yield to the power.
 
On many motors you cannot determine a sheared key by removing the nut only.-----And you cannot find a sheared key with a timing light.
 
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