Mercury 115 1988 I-6 WOT issues

sptjet90Reflexx

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I have rebuilt all 3 carbs with OEM kits. Installed new gas lines and I am using an external 6 gallon tank for testing. New stator and rectifier. 125 compression on all 6. And I cannot get her to run at WOT. She will idle/and run smooth until I try and push her. Then at WOT she will kick and sputter and try and stall out until I back down.

Anyone have a suggestion?
 

sam am I

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Did you set the float levels?

What's your fuel pressure?

Did you rebuild fuel pump?
 

Chris1956

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Pump the primer bulb while at high speed. If that fixes the issue, it is definitely a fuel issue. In addition to what Sam suggests, make sure the quick connect is working properly, the fuel filter/screen is clean and the fuel lines are at least 5/16" ID. 3/8" fuel lines are better.
 

sptjet90Reflexx

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I currently don't have a tool for checking fuel pump pressure. I will have to get one I guess. I am about to go to town so I will pick one up and report back on that. I did not rebuild the fuel pump. However I am running 50:1 premix and oil injection has been blocked off.

I removed the fuel filter for testing purposes as the tank is clean with no debris. I replaced quick connect fuel line with a new ethanol safe line and bulb.

I have a electronic en-richer I tried to push that in while at WOT and it had would try and stall. Should I still try the bulb test?
 

sptjet90Reflexx

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Alright the fuel pump PSI is between 4 and 5 psi at idle.

Really hope we can narrow this down!
 

Chris1956

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Yes, do pump the primer bulb at high speed. I suspect that is not your problem, but we need to rule it out.
Also, what kind of boat and what pitch prop do you have.
 

sptjet90Reflexx

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It is a 28' suntracker party hut with a 13p prop. I will go test the bulb thing now.
 

sptjet90Reflexx

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No change with squeezing the bulb. I am uploading a video to youtube of the run. I will post a link shortly.
 

Chris1956

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OK, then it sounds like you have ruled out the fuel system. Check for overheating, an then electrical issue. Not sure what to specifically suggest in the way of electrical issues, though.
 

sptjet90Reflexx

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The motor is always cool to the touch. Even the sparkplugs I could hold in my hands and they were not hot. I am about to go ohm out the trigger and make sure that is not damaged.. I should of replaced it when I replaced the stator.
 

sptjet90Reflexx

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I ohmed out the trigger wires removed from the switch boxes. They are all within 1100 to 1400 ohms. From what I read this is correct..
 

sam am I

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I have rebuilt all 3 carbs with OEM kits. Installed new gas lines and I am using an external 6 gallon tank for testing. New stator and rectifier. 125 compression on all 6. And I cannot get her to run at WOT. She will idle/and run smooth until I try and push her. Then at WOT she will kick and sputter and try and stall out until I back down.

Anyone have a suggestion?


Did you do all of the above in an attempt to fix this (a previous) WOT issue or, did this WOT issue come about JUST AFTER you perform the above actions?
 
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sptjet90Reflexx

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I have been trying to find this WOT issue since I got the boat. The only reason I rebuilt the carbs was due to the fact they were dumping gas out of the intake side which I thought could cause the surging.
 

inthedirtagain

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Sounds like it wants to run WOT, but stumbles due to a miss. You mentioned that the plugs are cool enough to hold and that raises some concern. Double-check that they are the right heat range for that year/size of Merc. I'm also wondering how strong the ignition is or if the plug wires are arcing. Do you know the age or condition of the wires? If not, I'd look and testing their resistance with a multimeter and then use a spark tester and look for a nice, fat spark on all 6. Don't recall what factory resistance specs should be on the wires and my manual doesn't state, either. Resistance goes up with age/corrosion/bad connections. Lower numbers are better.
 

sptjet90Reflexx

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Hmmm I matched the plugs to what was already in the motor.. maybe its possible they were wrong? They are weird plugs. I uploaded a image from google search. None of the wires appear damaged or cracking... I will check resistance on them.
 

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Faztbullet

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Check spark on all cylinder one at a time. Also remove idle stablizer if not allready discarded. It sounds like you may have a switchbox acting up or stator dropping high speed side ion one back
 

sptjet90Reflexx

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I have a new switch box on hand. Also have a new trigger on the way. Stator and regulator/rectifier I already replaced a few weeks ago. Idle stabilizer has already been removed.
 
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