I recently bought a new to me 2006 Merc 115 EFI....very low hours. When I tested it on the previous owners boat it ran well..I noticed at the time that the motor was warm and assumed he had already had it out for a run. Anyway now I have tested it on my boat and have a problem. The motor starts well but before the boat gets up on plane, around 2800-3000rpm - it misses on one cylinder and I have to back off the throttle a bit. After a few times of doing this it finally runs properly and have no problems the rest of the day. I recall the previous owners mentioning that he had replaced a couple of injectors on it and in hindsight I think that is odd for a motor with so few hours on it. My best quess is that its either another injector crapping out or plugs...Anyone have any suggestions?
Merc 115...Injectors or plugs?
- Thread starter wet spot
- Start date
fogged in
Well-Known Member
would be REALLY surprised if it were plugs. Hi voltage ignition, plugs last forever!
salmonkiller01
Well-Known Member
Run some mercury quickly thru it and see if it cures it. My opt would do the same thing if I did not run it with quickly regularly
Cuba Libre
Well-Known Member
Ask the question on the iFish boat doc page http://www.ifish.net/board/showthread.php?t=3731&page=83 The guy is an excellent Merc mechanic
triplenickel
Well-Known Member
If it's consistent enough to reproduce at will, trouble shooting shouldnt be impossible. Try to figure which hole isn't firing, pulling a plug lead off usually works. If you can find the hole you're laughing, swap suspect parts with a different hole and see if the problem follows.
sudsy
Well-Known Member
Could be your throttle position sensor...I have a 2005 merc 115 EFI and had a similar propblem and after troubleshooting found it was a bad TPS. Its simple to check if your handy with a multimeter, the TPS basically has 3 cables running to it, 5volts in, ground, and output voltage to ECU, with the motor off ut power applied to motor, you want to have someone watch the output voltage while you run the motor through its full range of throttle, mine had a dead spot around the 4500 rpm range where the voltage would be climbing up to 2.3 volts then drop back down to 0 volts then back up to 2.7 volts.
Might be worth checking out given your symptoms.
Cheers
Sudsy
Might be worth checking out given your symptoms.
Cheers
Sudsy
uclueletcharters
Well-Known Member
Word of advice take it to the shop and have them plug it in. If an injector is shot or faulty and you keep running it you will fry the cylinder guaranteed. In the old carb days you could fiddle around but when it comes to injection it's the same as your car has to go to the shop and be plugged in. Even if you trial and error if you misdiagnose and by the wrong part there's your shop diagnostic labor cost. Do yourself a huge favor and take it to the shop, a certified shop.
Island Fish Lifter
Well-Known Member
sometimes you actually get good advice here, this is it.
Island Fish Lifter
Well-Known Member
Great idea! lets take everything to a shop! So that next time youre 20 miles off shore and you wont "go", you wont have the foggiest idea what to look at! Crap!
Island Fish Lifter
Well-Known Member
Great idea! lets take everything to a shop! So that next time youre 20 miles off shore and you wont "go", you wont have the foggiest idea what to look at! Crap!
Island Fish Lifter
Well-Known Member
damn, some of you guys are not the type of people I would want to be 20 miles off shore with
Hoochiebob
Well-Known Member
Have to agree with IFL, take some time to learn your motor. A somewhat hit and miss diagnosis may cost you some up front, but the knowledge you gain from troubleshooting your own engine will pay dividends when you do have trouble on the water. Do the legwork and get more familiar with your engine. You can always use a mechanic when you are stumped.
It sounds like you are trying to figure it out yourself, and good on you. The tps is a notorious problem and a good place to start
It sounds like you are trying to figure it out yourself, and good on you. The tps is a notorious problem and a good place to start
uclueletcharters
Well-Known Member
LOL that's why all boats should have an auxiliary motor just in case your main acts up. Learning is a good idea and I hope your able to figure it out on your own on your first try. Don't run it if it's not quite right because it will most likely burn the motor out if there is a fuel related issue ie injector, fuel rails, diaphram and the list goes on that could cause a motor to lean out. Good luck hope it all works out for the best what ever way you choose to fix it. Just would hate to see someone take advise from someone that maybe is a mechanic or next to as good of one saying it's no big deal as were all not as mechanically incline as others. If your tapped for cash you could try at idle listening to each injector make sure they are each clicking the same as each other and or pull your plugs to find out which cylinder it is based on colour to isolate the issue. If you find the injector you can used a 9V battery to open up the injector to clean and put some lube in there. You will need to rig wires from the battery to the injector while it's out and unplugged from the harness. Mercs from my experience are injector pigs! I think you can test your tps with a standard voltage meter as someone in an earlier post explained, I did replace a TPS unit and the symptom was one of my twins was surging. If it was the TPS it's an easy change. Could be a goofy coil as well or a bad ground / wire connection check all the pluggins and look for any chaffing where wires rest against and hard parts of the motor. Could the motor be going into guardian mode intermittently another reason to get the codes stored on the motors ECM. Maybe you have a sticky thermostat that's eventually pops open but at a certain point the motor gets to hot and guardian mode kicks in? So may things it could be.
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sudsy
Well-Known Member
All really good advice, I often listen to my injectors to make sure they are working correctly, use a screwdriver and place it on the one you want to listen to and put it up to your ear. yes, a standard voltmeter works for checking the TPS, can be done with measure either the voltage or the resistance. I have learned a lot about EFI four strokes by doing my research and fixing problems myself, but I always check with the merc mechanic downtown Vic and run stuff by him before I do it. He has always given me advice for free where I'm buying the parts from him...usually he gives me some help with things that I can check myself and I also have the shop manual which is a huge help and really teaches you what's going on in the motor, solid investment if you don't already have it.
Thanks everybody - lots of ideas. One thing I did notice when I tried the motor lately is that when it begins to miss I just have to back off the throttle a hair...almost imperceptible...and that would stop the miss...it didn't really seem like it would be a plug or injector...makes me think that the TPS could be suspect so that and the seafoam will be first on my do list in a week or so.
Terry
Terry
Thanks everybody - lots of ideas. One thing I did notice when I tried the motor lately is that when it begins to miss I just have to back off the throttle a hair...almost imperceptible...and that would stop the miss...it didn't really seem like it would be a plug or injector...makes me think that the TPS could be suspect so that and the seafoam will be first on my do list in a week or so.
Terry
Terry
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