Have Boat Questions? Ask a Boat Repair Expert.
Hello my name is ***** ***** am I speaking with? I read what you wrote. Mercury outbaords are cataloged by serial number, can I get that number so I can see which version of the 115 you have? Next, are you able to check things like spark output and fuel pressure?
HI Chris. Lets start with the basics. Is the emergency stop switch clip in place?
I don't want to get your hopes up to high on this one. Being and EFI engine, if the problem is ultimately some sort of sensor issue, we are not going to find it without a scan tool. However, we can check some of the basic things. Are you willing to get a fuel pressure gauge, as well as an adjustable gap spark tester? Something like this, in this link - https://www.amazon.com/Thexton-THE404-Spark-Tester/dp/B0002STSBM/ref=sr_1_9?s=automotive&ie=UTF8&qid=1522013287&sr=1-9&keywords=spark+tester Also, do you have any starting fluid?
Yes you can use those tools. On the spark, just unplug the coils, plug it into the spark tester, crank the engine over, and see if there is spark on the tester. Just do 1 at a time on those. On the fuel pressure, just hook that up to the Schrader valve, cycle the key from off to run 3 times, and then see what the pressure reads.
but if I turn the key to run and press down to prime I got around 40 psi.
Okay that is not normal. Out of curiosity if you push the key down, and then hold it down and turn it to start at the same time, will the engine start or attempt to start?
Do you have a volt meter so we can test the key switch itself?
When you get a chance pop the key switch out. Then hook you your meter to the purple wire on the back of the switch. Let me know if that wire shows 12V or not when the key is in the run position.
I'm actually about to log off for the evening, almost bed time for me, and we can pick this back up in the morning. But just to confirm, the fuel pumps come on when you push the key switch IN? Is that correct?
Good morning. This key switch isn't working the way it is supposed to, and I'm confused by what you are witnessing. I just want to confirm. If you turn the key to RUN, you do not hear the fuel pumps kick on? However, if you push IN on the key switch, you hear the fuel pump run. Is that all correct?
If what you say is accurate then you either have a bad key switch or some kind of short circuit in the wiring harness. Pushing "IN" on the key switch should not do anything on your engine. The IN position is for older carbureted engines. They simply use the same key switches because they are universal. On your engine, the fuel pumps should come on when you turn the key to run. At this point you would replace the key switch, and if for some reason that doesn't fix it, then we have to hunt for a short circuit and try and find it.
Let me know how you make out.
Okay Chris let me know how you make out.
Here is kind of what I am having a hard time understanding. When you turn the key to run, this powers up the purple wire. The purple wire is what powers up the main power relay on the engine. The main power relay is what kicks on the fuel pumps. When you push the key IN, the key switch powers up the yellow with a black stripe wire. If this was a carbureted engine, that yellow/black would power up the choke. However, on the EFI engines, that yellow/black wire that comes off the key switch isn't attached to anything. It should be there just hanging off the back of the key switch, but not actually connected to anything. When you tell me that when you push your key switch IN and the fuel pumps come on. That tells me that the key switch is powering up the purple wire when you push the key IN, which it should not be doing.
Have you ever personally seen this engine start?
Not that this should matter all that much. But if you turn the key to run, and then push it in, does that yellow/black wire show power with the key pushed in?
At this point I have no idea why the fuel pumps are coming on when you push the key to start. The 2 electrical circuits (the choke circuit and the ignition circuit) are not even connected, so I have no idea why it's happening. I will opt out and leave your question open to the community.
Hello, my name is***** you still require assistance on the engine?
Yes, what is the brand of your boat?
Can you unplug that yellow/black wire and see if the engines fuel pumps will run with the key turned to on?
Great. I look forward to it.
When you get out to it, also look to the engine connector for the main harness. It is a large round connector. Unscrew it and disconnect it from the engine. Then give the boat side of the plug a slight wiggle or tug to see if the cable end will come off or stay. I have seen them come apart in the past.
Your very welcome. Ill talk to you when it dries out some.
Has the connector between the engine and the boat come apart in the past? It is the large round connector on the right side of the engine. Disconnect it and make sure that all is still ok there.
Ok, does the fuel gauge read out when the key is just turned to on? Or does it only read when you push the key in?
Can you take that 12 pin connector apart in the dash, the white one you mentioned earlier, and see if any of it is melted?
Is the new key switch in yet?
I feel that since you already have it, might as well put it in and start eliminating things. All the tests are coming back as good, but there is something that is just not right.
Before you install the switch, try and get a look at the entire run of the harness between the key and the engine. Make sure that there are no breaks or chew marks in it. I have seen rodents tear up some over storage times.
You can test the power to the relay. the 12V + is on the yellow or purple wire going to the relay. It is only there for the first few seconds after key up.
Did you look at the harness from the engine to the motor?
Have you seen this engine run?
Have you done anything to the batteries since it last ran?
do you have a piece of scrap wire, I have an idea for a test.
do you have a helper to do the key on test?
Would be interesting to know.
Yes it can, that is why I mentioned to check the harness from one end to the other.
What does it get up to?
Can you take one of the trim relays and swap with this relay to see if the voltage stops?
That would be a back feed due to no ground to kill it from the ECU and the key switch.
For the wire, unplug the key switch at that 12 wire plug in the dash, then jump, using that scrap wire from the red to the purple and see if the pumps run on the engine.
Have you also looked at the harness from the helm to the engine?
Also, have you had anything installed or removed that would require part of the rear of the boat ro come up?
There is that corner plate in the rear of the boat that can be taken up to give you a bit of a look. It will be screwed to the floor and possibly to the side as well. Using a phillips screwdriver to move the carpet around, you will find the screw heads.
Sounds good. The plate where the control box is mounted will come off too if needed.
If you have had anything installed, even a transducer, there is the possibility that a screw has gone thru the harness and that is causing this whole mess.
Look around the areas where you mounted that antenna, there may be an issue. As a test you could pull the mounting screws from it and see if the engine behaves correctly.
That is good news. But not really.
There are a couple. But pushing in the key should not over ride them. Question, is there a primer bulb in the fuel line?
Ok, on the upper left side of the engine there is a green cap. Remove it and press in on the schreder valve inside there. It may help to follow that hose to where there is a quick connect, then press in on the red or blue tab on the connector and seperate the two hoses. What you are looking for is any fuel that may come out of this hose.
This cap is on hose 8 in the diagram.
The canister is the vent purge valve. It is controlled by the ECU as to when it will open and close. Since you did not get any fuel from that hose, unplug the harness from that valve and try your key again.
Ok, press on the schreder valve in the high pressure fuel line going to the injectors and see if you have pressure there.
Does it seem to want to fire at all?
If not, pull one pf the plugs and see if they are wet
Ok, plug in that sensor to stop the alarm and check those pumps again.
Is any sensor unplugged?b That code is for a sensor.
That would also include the coils.
Yes you can do it that way. Make sure that the tester is plugged in firmly to the coil.
It is easiest to unplug the cils before taking them out.
Yes, but set that gap to 7/16"
Is the kill switch at the control box connected and on?
Try the spark with the large round 14 pin connector disconnected. You will need to jump the solenoid again.
Still have that multimeter? If so, unplug the crank position sensor, and do a resistance test on it. It needs to be 330 Ohms.
Under the plastic cover on the top of the engine. Pointed at the flywheel. It has two wires coming from it to a plug in.
It is good.
I think at this point it really may need to get into a Mercury shop and be connected to the computer so that the cause of the alarm can be determined.
I was hoping that we could get thru it as well. I hate to send them to the shop at this point, but we have done about everything that can be done without the computer on it.
I was sitting here thinking, your engine should still be under the factory warranty also. Make sure that the dealer checks the status on it.
Ugh, Gold is ok, it has its imitations though. Most everything electronic is not covered on it. BUjt if the standard warranty recently expired, maybe the dealer can make a call to Mercury to get at least the parts covered and you only need to cover labor. This can still save hundreds on a repair for even just a fuel injector.
It should, we went through allot of items.
Just as a quick last test, turn off the kill switch, then see if the pumps turn on when the key is turned to run.
That is enough battery volts to run the ECU while cranking. I hate to send one in after everything that has been done, so the kill switch was just a thought.
I would really be interested to know what they find out for sure.