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2014 Mercury Four Stroke Serious Hesitation at 3,000 RPMS, problem stops after anchor and return

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bigpips305

New member
I have a nice 2015 (NOT 2014) Mercury Fourstroke. It is serviced regularly, and still under warranty but our local shop is backed up for weeks for dockside service, which they insist is necessary to check the motor and duplicate the symptoms.

Lately, after crankling and idling perfectly out of the canal, when attempting to accelerate and get on a plane, right at or right about 3,000 RPMS, there is severe hesitation/misfire. It as if its loosing 2 cylinders of spark. The motor is literally jumping up and down back and forth. You fear it would rip right off the transom. It runs great and still planes at about 2400-2800, so this is the speed we cruise at to our destination. If you try turning it off and back on any time in early on in the trip. The symptom is the same. However, once we reach our destination. Sometimes a half hour cruise, sometimes only a 5 minute cruise, anchor and shut the motor down for some time, upon restarting and heading back the motor runs fine. It will run all RPM ranges and cruise nicely. SOMETIMES, cruising back at 3500 or more, randomly, the symptom will intermittently return, causing an immediate decline in RPMS and sending any poor souls standing flying to the front of the boat. Ive checked for water in the fuel, spark plugs, and connections. Any ideas?????
 
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Also, there is another symptom. When it has this problem, the motor will trim down, but not up. I am able to recreate this symptom by unplugging the center front harness from the metal plate.
Also, there is a hissing noise coming from the left side of the motor (facing transom from deck of boat), sounds like air pumping out and gets louder as engine increases RPMS, when you shut down the motor, a purge of air like a blowoff valve shoots out from somewhere. Sounds like a PSSSSSSSSST
 
It sounds like you are hitting the in neutral rev control. That will limit the rpms to 3000 in neutral. It will also limit the rpms in gear if the ecm(computer) does not see the shift switch activate.

Disconnecting the harness and making the problem occur is probably because you are disconnecting the trim sender which will also limit RPM, (over trim rev limiter)
 
It will go above 3000. But it will spit and sputter and the motor will shake like no tomorrow. And on the return trip sometimes it will be fine. Running 4500 or so, cruising back and almost like you unplugged 2 spark plugs as you were flying it will start bogging and throw everyone to the front. It really starts right about little before 3000. hard to tell with analog tach gauge. But if I go outside right now and crank it up. Gear or neutral, it will run great under 28,29,3000 or so and be all hell after that. So ill cruise at 2500 ocean side. Anchor, fish. Crank up and return. Sometimes ill get lucky on the way home. But if i do, i am carefeul because it could just start happening anytime.
 
My dad said he got a 6 beep alarm today during his charter as well.. The first and only time we ever heard this, was the other day while trying to diagnosis this issue. I tried to rev the motor up to 3000 in neutral it was giving the same sputter and misfire symptom and i let it stay steady for about 5 seconds, and then all of a sudden is was like the symptom stopped, the motor starting revving up smoothly and very quickly, and the alarm went off. Based on what you said, that sounds like the rev limiter. But this also implies that the problem is prior to the 3,000 mark. As if I couldn't even get to the rev limiter successfully due to this issue, and then the problem ceased intermittently and allowed it to rev to the limit.
 
I had something similar with my merc I found that some of the spark plug connectors had rattled loose could be the same maybe not worth a look?..
 
I've checked all connections, plugs, wires etc.. I've checked all hoses, fuel lines and filter, ignition and throttle. I do believe this is an electrical problem.
 
30days wait. They insist dock side to recreate symptoms and they are booked solid. We ru charters every day that's why I hoped.to get some help.here
 
bigpips305 said:
I have a nice 2015 (NOT 2014) Mercury Fourstroke. It is serviced regularly, and still under warranty but our local shop is backed up for weeks for dockside service, which they insist is necessary to check the motor and duplicate the symptoms.

Lately, after crankling and idling perfectly out of the canal, when attempting to accelerate and get on a plane, right at or right about 3,000 RPMS, there is severe hesitation/misfire. It as if its loosing 2 cylinders of spark. The motor is literally jumping up and down back and forth. You fear it would rip right off the transom. It runs great and still planes at about 2400-2800, so this is the speed we cruise at to our destination. If you try turning it off and back on any time in early on in the trip. The symptom is the same. However, once we reach our destination. Sometimes a half hour cruise, sometimes only a 5 minute cruise, anchor and shut the motor down for some time, upon restarting and heading back the motor runs fine. It will run all RPM ranges and cruise nicely. SOMETIMES, cruising back at 3500 or more, randomly, the symptom will intermittently return, causing an immediate decline in RPMS and sending any poor souls standing flying to the front of the boat. Ive checked for water in the fuel, spark plugs, and connections. Any ideas?????
Click to expand...


Hi there, did you found out what the problem was? my 150hp 4 stroke Mer is doing the same thing. this weekend it dies when it started to jump up and down trying to right off the transom. now, it can't get over 1500 rmp, if over it will do the jump up down thing and dies. High pressure pump motor dead or dirty fuel line???
Thanks
 
I have the Sam problem with my 2011 90 hp mercury four stroke so far low pressure pump , high pressure pump , VST Tank ,gas line ,prime bulb, pickup tube and fuel filters still the same going back in shop tue let you know
Kelvin
 
I am having a very similar issue. Mine is much more intermittent and typically on occurs 2900-3500 RPMs. When mine starts stumbling i can give it throttle and it will run fine. See link to two different videos. I ran the motor at 2900-3100RPMs for 1.5 hrs before the issue occurred. (Shown in video) then I bumped the RPM up to 3500-3600 for about 5-10Mins then up to 4700 RPM for another 30 min and this issue never came back even after returning to 2900-3100 for 15-20min. If anyone has any input it would be appreciated. Dealer trying to narrow this down now. FYI these videos and the above description was done with a temporary wiring harness to eliminate my harness in the boat causing any issues. So the issues in motor related not harness related.
https://www.youtube.com/watch?v=CRXpwaLAdEI
https://www.youtube.com/watch?v=EieKNWOW2lU&feature=youtu.be
 
bigpips305 said:
I have a nice 2015 (NOT 2014) Mercury Fourstroke. It is serviced regularly, and still under warranty but our local shop is backed up for weeks for dockside service, which they insist is necessary to check the motor and duplicate the symptoms.

Lately, after crankling and idling perfectly out of the canal, when attempting to accelerate and get on a plane, right at or right about 3,000 RPMS, there is severe hesitation/misfire. It as if its loosing 2 cylinders of spark. The motor is literally jumping up and down back and forth. You fear it would rip right off the transom. It runs great and still planes at about 2400-2800, so this is the speed we cruise at to our destination. If you try turning it off and back on any time in early on in the trip. The symptom is the same. However, once we reach our destination. Sometimes a half hour cruise, sometimes only a 5 minute cruise, anchor and shut the motor down for some time, upon restarting and heading back the motor runs fine. It will run all RPM ranges and cruise nicely. SOMETIMES, cruising back at 3500 or more, randomly, the symptom will intermittently return, causing an immediate decline in RPMS and sending any poor souls standing flying to the front of the boat. Ive checked for water in the fuel, spark plugs, and connections. Any ideas?????
Click to expand...

I had the same problem, after first dealer had my boat for 2 weeks and changing fuel filters, spark plugs, oil filter, and finally the ecm computer boat still wouldn't go over 3000 rpm. I then took boat to another dealer that was Mercury certified turned out to be my trim position sensor. The second shop knew the problem within 10 minutes and had part next day and fixed. Make sure to go to a certified Mercury dealer they have proper computer software to diagnose.
 
Nb sparky said:
I had the same problem, after first dealer had my boat for 2 weeks and changing fuel filters, spark plugs, oil filter, and finally the ecm computer boat still wouldn't go over 3000 rpm. I then took boat to another dealer that was Mercury certified turned out to be my trim position sensor. The second shop knew the problem within 10 minutes and had part next day and fixed. Make sure to go to a certified Mercury dealer they have proper computer software to diagnose.
Click to expand...

I mentioned that in Post #8.
 
I looked at the videos and that is exactly what is going on with my boat. I think its the NS switch in the motor but wanted to know what you did to fix your issue? If it was the Neutral safety switch do you know where the thing is located? I was totally unable to find it (looking on line) and even if the Mercury 4 stroke 150 has one in the motor but I am guessing it must?
Thanks,
 
Buzzbay, funny, I was looking for help with my same issue looking at old threads so surprised to see a reply from earlier today. I've been dealing with the same problem since summer of 2018. Started as a rare hiccup, now can't get over a certain rpm to get on plane. 3 different mechanics and 4 visit. Of course it usually doesn't do it for them when in shop, but right away, does it for me. I'm taking it into mechanic this friday for final time. I told him if he starts it and it runs fine, keep it a few days and try again. If this doesn't fix it, I'm repowering. I have a 115 and would love a 150. The pickle is I can sell this for about $6100-6900 but only if running good. 2013 115 with only 200 hours. Should have several more yrs and hundreds of hours left. next motor won't be a Mercury. So we/I have it narrowed down to fuel float, mechanic from my video says rev limiter. Other mechanic trying to get me to shell out $2-3000 for an ECM. New mechanic said hardly ever needs to be changed and expensive gamble. From above, and maybe a few are the same thing, but I'll ask my mech to check out, trim position sensor, over trim rev limiter and neutral safety switch. My engine when cutting out a bunch would send a code for two different things and I changed both to no avail; crankshaft position sensor and shift switch. I wonder if the bucking would throw off the other sensors. I think the neutral safety switch is the shift switch, but I'm not sure. On my motor, it is under everything, where the shift wires enter the bottom of the motor. I bought one from a dealer for $50 but couldn't access it so had this other mech change it. Didn't help.
 
Bisealund,
Thanks for the info. I am still going to try and see if that fixes the issue. If not i will be back to looking for the next thing it may be. As you said the tech's who have seen it (2 total) have not found anything wrong with the motor. Thanks for the input and let me know what the next person says. Good luck.
 
BuzzBay19cc said:
Bisealund,
Thanks for the info. I am still going to try and see if that fixes the issue. If not i will be back to looking for the next thing it may be. As you said the tech's who have seen it (2 total) have not found anything wrong with the motor. Thanks for the input and let me know what the next person says. Good luck.
Click to expand...

So my mechanic is pretty positive it is the wiring harness. They were finally able to repeat the hesitation in the shop and could cause and fix by moving wires. Makes sense as slowly got worse over time, and it would go away when I would raise motor, fiddle with stuff, moving wiring around, then would return. He thinks at a certain RPM the harmonic vibration was enough to cause issue, and that early on, if and when I could get past that point, it would run fine at higher RPMs. so $1500-1600 including labor, and should have it by this weekend. I'm hopeful.
 
Has anyone found a definite cure for this issue??

I have the very same issue on my 2015 150's (about 750hrs each) It started last summer with one motor. Per recommendation of my local dealer I started replacing the ignition coils as a process of elimination. I ultimately had the injectors cleaned, all filters and plugs changes and inspected every possible connector and as much of the wiring system as possible. The problem seemed to have been fixed only to reappear two days ago on a charter. First, the same motor as last year and after another coil change on the water the other motor started with the same issue on the way home. One thing I did find is that when you bring the motor to idle and let it "cool"down (considering I run it around 3800rpm), the problem seems to fix itself for a while. I also found that if I just open her up to around 4500rpm it goes away for a while.

These motors are run and treated with the utmost of care and stored in a heated building when not in use. corrosion and lack of care is NOT an issue.
 
I believe I may have found a solution to this issue. After consulting my local dealer we took stock of the events that lead us to where we were as far as figuring this thing out. I live in a very active fishing community and numerous boats rune the 150 merc's. None of the guys I spoke with had this issue on any of their motors. However, the power settings everyone else runs at are 4000 and above. I run my motors at 3500-3800. It lead me to believe that maybe I am building up some kind of carbon due to prolonged low power settings. I started using a fuel stabilizer for a cleaner fuel burn and have been running my motors at 4000 + RPM. I just boated quite extensively over the last week and have had no issues recurring issue thus far. Holding my thumbs and hoping this is it........
 
I had this issue on a 2010 90hp 4 stroke EFI and it was the neutral safety switch. You can test this by removing the wiring harness. The part is $40 and can be replaced easily. The harness is located in the front of the engine and is bolted to the bottom of the cowl. When shifted to forward it disengages and when in neutral it is engaged. The harness has a button in the front which is spring loaded as you will see if you move the shift lever. When unplugged you can rev past 3000 rpms. I did this with muffs and hose. Hope this helps someone.
 
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