Mygreenihc
Seaman Apprentice
- Joined
- Mar 14, 2012
- Messages
- 46
Hello guys,
I typically do not post a question until I have done everything that I can think of to fix a problem. I have worked with this issue for quite some time and do not know what else to look for. I hope someone here has seen this before or has a suggestion that will resolve my issue. First off, this is a 1996 Mercury 115 ELPTO. It is an inline four cylinder and has the two carbs with no idle jets and two with idle jets. Here is what I am seeing and what I have done so far to resolve it.
What I am seeing:
At idle, the engine runs fine. Nice and smooth for as long as I want to idle. No idle problems that I can see. When taking off, this thing comes out of the hole great, plenty of power, and shoots off like a rocket. I can consistently out run my Dad's 150 Yamaha and brother 250 Pro XS for the first 200 yards. (you have to brag about whatever you can when you run a 115) My problem shows up around 4500 rpm's or so and up. If I hold the throttle at about 3/4 open, it will pick up and drop off randomly by 3 to 400 rpm's. At times, I can slowly work it up to 4800, but at other times I cannot get it above 4600 and in all cases, it will not stay there more than a few seconds. I have, on very few occasions, be able to get it close to 5k, but then it drops right back down. Sometimes it eases back up slow and others it picks the nose of the boat up and shoots off, just for a few seconds. I have noticed too that if I back off of the throttle a little, it will start working its way back up, but if I push it to WOT, it goes flat and will not gain any more speed, but quits surging..
Here is what I have done to resolve the issue: (Note, all of the parts replaced were with new OEM parts except for Stator, trigger, and switchbox, which were new CDI replacements.)
Compression check shows all four cylinders between 126 and 128.
Tested spark using spark gauge (connects to end of wire and grounds to block)
Pulled my fuel tank and clean/dried it before reinstalling with fresh 91 octane fuel.
Replaced tank vent with new vent and hose.
Replaced fuel line from tank to engine with new bulb.
Replaced all fuel lines and filters on engine with new modern fuel line.
Rebuilt fuel pump with OEM kit.
Rebuilt all four carbs with new OEM kits.
Replaced Stator, trigger, wiring assembly, switchbox, coils, plugs and wires.
Tediously checked throttle linkage and checked that all butterflies are opening completely and together. There is no play in any of the butterflies.
Not related, but this engine has a new control box and cable from the cockpit, and a new solenoid and starter.
There are only two things that I can think of that I did not do, one is when I rebuilt the carbs, I did not run a drill bit through the jets. I did not see any buildup anywhere in the carbs or in the jet passageway and I did not have an .062 and .064 drill bit on hand. The second thing is that I did not remove the pickup tube from the tank when cleaned it. Another thing to note is that this engine has never had any ethanol in it that I know of and I have owned it since it was new, always pure gasoline.
If anyone can help, I will be very appreciative.
Thanks,
Brad
I apologize for writing a book, but I wanted you to know exactly what I have.
I typically do not post a question until I have done everything that I can think of to fix a problem. I have worked with this issue for quite some time and do not know what else to look for. I hope someone here has seen this before or has a suggestion that will resolve my issue. First off, this is a 1996 Mercury 115 ELPTO. It is an inline four cylinder and has the two carbs with no idle jets and two with idle jets. Here is what I am seeing and what I have done so far to resolve it.
What I am seeing:
At idle, the engine runs fine. Nice and smooth for as long as I want to idle. No idle problems that I can see. When taking off, this thing comes out of the hole great, plenty of power, and shoots off like a rocket. I can consistently out run my Dad's 150 Yamaha and brother 250 Pro XS for the first 200 yards. (you have to brag about whatever you can when you run a 115) My problem shows up around 4500 rpm's or so and up. If I hold the throttle at about 3/4 open, it will pick up and drop off randomly by 3 to 400 rpm's. At times, I can slowly work it up to 4800, but at other times I cannot get it above 4600 and in all cases, it will not stay there more than a few seconds. I have, on very few occasions, be able to get it close to 5k, but then it drops right back down. Sometimes it eases back up slow and others it picks the nose of the boat up and shoots off, just for a few seconds. I have noticed too that if I back off of the throttle a little, it will start working its way back up, but if I push it to WOT, it goes flat and will not gain any more speed, but quits surging..
Here is what I have done to resolve the issue: (Note, all of the parts replaced were with new OEM parts except for Stator, trigger, and switchbox, which were new CDI replacements.)
Compression check shows all four cylinders between 126 and 128.
Tested spark using spark gauge (connects to end of wire and grounds to block)
Pulled my fuel tank and clean/dried it before reinstalling with fresh 91 octane fuel.
Replaced tank vent with new vent and hose.
Replaced fuel line from tank to engine with new bulb.
Replaced all fuel lines and filters on engine with new modern fuel line.
Rebuilt fuel pump with OEM kit.
Rebuilt all four carbs with new OEM kits.
Replaced Stator, trigger, wiring assembly, switchbox, coils, plugs and wires.
Tediously checked throttle linkage and checked that all butterflies are opening completely and together. There is no play in any of the butterflies.
Not related, but this engine has a new control box and cable from the cockpit, and a new solenoid and starter.
There are only two things that I can think of that I did not do, one is when I rebuilt the carbs, I did not run a drill bit through the jets. I did not see any buildup anywhere in the carbs or in the jet passageway and I did not have an .062 and .064 drill bit on hand. The second thing is that I did not remove the pickup tube from the tank when cleaned it. Another thing to note is that this engine has never had any ethanol in it that I know of and I have owned it since it was new, always pure gasoline.
If anyone can help, I will be very appreciative.
Thanks,
Brad
I apologize for writing a book, but I wanted you to know exactly what I have.