2002 Merc. 115-will Not Go Over 4000 Rpm

[PHILLY9]

Could Someone Tell Me Some Of The Basic Problems To Look For On My 2002 Merc. 115 4 Stroke. It Starts Good And Runs Good At Low And Moderate Speeds, But Will Not Go Over 3800 To 4000 Rpm. Some Of The Things I Have Already Done Are: New Plugs And Gas Filter,fresh Fuel,had The Throttle Adjusted And The Prop Checked. It Used To Go About 43 Mph And Now Will Only Reach About 30 Mph. Help!!!!

 

[Bigjohn1]

Re: 2002 Merc. 115-will Not Go Over 4000 Rpm

Very important - 2-stroke or 4-stroke. We need to know this as your troubleshooting is going to be a bit different depending on which it is.

 

[PHILLY9]

Re: 2002 Merc. 115-will Not Go Over 4000 Rpm

This Is A 4-stroke. Thanx For Your Reply.

 

[sburdy]

Re: 2002 Merc. 115-will Not Go Over 4000 Rpm

I had a similar problem with my 2002 30 HP 4 stroke fuel injected Merc. Started with intermitant dying and graduated to not running over 3000 rpm without stopping.
There are two fuel pumps.
A mechanical one at the back of the engine and an electric one on the starbord side, in side a cast aluminum 1/2 quart tank.
The diaphram in the mechanical pump starts to disintergrate and the rubber contaminates the fuel system. Fuel filter is before all the pumps.
The floating rubber debris plugs the orfice that feeds the tank which the electric pump sits in.
You need a new mechanical pump and need to clean the electric fuel pump assembly.
I installed a second inline filter between the mechanical filter and the electric one to prevent a repeat.
Hope this helps.
PS Merc isn't making enough MONEY selling fuel pump kit for $9 so you have to buy a $150 pump and throw the old one in the land fill. So much for buying a enviromentally friendly outboard.

 

[Bigjohn1]

Re: 2002 Merc. 115-will Not Go Over 4000 Rpm

PHILLY9,

I got your PM but it has taken a while to respond due to a recent illness. The issue sburdy brings up is valid and is a possiblity. Still, you need to troubleshoot it to at least a basic degree where you know whether it is a "fuel" or a "fire" problem. It could be either since we are talking an outboard which is 5 years old. The rubber in those fuel pump diaphrams does not last forever and COULD be your problem. Still, your particular engine's ECM has host of sensors it relies upon to set idle and engine timing. There are 2-3 fault conditions (in the ECM) which will cut power to one or two cylinders and limit your rpm's just like what is hapening tp you right now.

If you haven't already had it to the shop for troubleshooting, you are not out much $$ by simply purchasing a new low pressure fuel pump diaphram and seeing if that cures it. If not, the ECM is quite likely getting a faulty input from the Crank Position Sensor or the Oil Pressure Sensor ....OR...the ECM itself is faulty and must be replaced. Unfortunately, this engine is not that easy for a backyard guy to troubleshoot electrically. Not becuase you don't know what you are doing but rather, you need a whoe host of SPECIAL Mercury wiring adapters. These various adapters go between a standard digital multimeter and the wiring harness.

If you want more specifics on what I am saying, just look at an official factory manual for this engine and go through the elctrical troubleshooting procedure. You will see listed no less than 5 special adapters you must use to isolate the multimeter to the correct wires in the harness.

GOOD LUCK!

 

[PHILLY9]

Re: 2002 Merc. 115-will Not Go Over 4000 Rpm

Thanks Again Bj1. Hope Everythings Ok With The Illness. Been There!
Anyway, I'm Still Trying To Find The Time( And Energy) To Take The Boat To The Water To Check Some Basics. I'm Trying New Plugs Again And Pump The Ball While Underway And Opening The Fuel Cap To See If Maybe The Vent Hose Is Clogged. I Got These Ideas From My Manual. It Is A Clymer Manual And I Have Recently Heard That They Are Not Very Good. I Did Take It To The Shop And Paid Them $80.00 To Drain Some Of The Oil Because They Thought I Had To Much Oil In It And That Was Causing My Problem. Well, After I Took It To The Lake And Found Out That Was Not The Problem, I Checked The Oil Level And It Was Below The Low Mark. I Don't Think It Did Any Damage. Anyway, Do You Think It Would Be Bad To Run The Motor Like It Is? My 2 Boys Are Really Counting On A Walleye/perch Trip To Lake Erie.

 

[captadamr]

Re: 2002 Merc. 115-will Not Go Over 4000 Rpm

I have to 2002 Merc 115 4Strokes on my Angler. Just this weekend I had a problem similar to yours, one engine would not get over 3000. Tested to see which cylinder was out (by unplugging the injectors one by one and lisiting to hear which cylinder was not runnning. I AM NOT SURE IF THIS IS RECCOMENDED, SO TRY AT YOUR OWN RISK) I determined that the #2 and #3 cylinders were not running, took it to the mechanic thinking a bad coil or ECM problems, he took a screw driver, tapped the fuel rail between the 2 injectors and ta-da it was fixed. So long story short, maybe you have a sticky injector.

I think i will replace them soon but the $$$ is painful after replacing one ECM.

 

[PHILLY9]

Re: 2002 Merc. 115-will Not Go Over 4000 Rpm

thanks. i'll get out my trusty screwdriver and give it a shot.

 

[limulus]

Re: 2002 Merc. 115-will Not Go Over 4000 Rpm

I also have this same problem with revs on my 2007 115 4-stroke. I've had this engine now for a month and it has 12-hrs. Two weeks ago, I was seeing around 4000 RPM and now, I'm only seeing about 3800 RPM.

The dealer told me to vary the revs the first 10-hrs which I did. I always thought that the 4k max I was seeing seemed a little low but assumed that was because it was a 4-stroke. I checked the specs and see that this engine should do over 6000 RPM. The dealer is about 80-mi from the location of the boat, so I'm getting a separate Merc dealer to take it out of the water to check it out.

I certainly hope I'm not going to hate this motor.

 

[PHILLY9]

Re: 2002 Merc. 115-will Not Go Over 4000 Rpm

i think you will love this motor once it gets fixed up. i still haven't solved my problem, but now i think it is a problem with #3 cylender. when i changed the plugs it looked like 3 cyl. spark plug was never fired. #4 plug looked a little fouled and #1 and 2 looked normal. this was after only about 5 hours of run time. you might want to look at your plugs.