Mercury 115 4S problem

[BartMan]

Had an issue yesterday with my Mercury 115 4s (2011). Got to the ramp, started up fine, powered off the trailer and parked it on the courtesy ramp. Left it idling while I went and parked the trailer. We also had to wait for another family to arrive, so for about 20 minutes the motor idled perfectly fine. About the time we were ready to leave, it started idling extremely rough (enough to shake the pontoon) and stalled. I tried for ten minutes to get it to start, and sometimes it would start fine, then idle fine, then again start idling rough and stall. I finally disengaged the gears so I could give it more throttle and it started, but would rev to 3000 rpm, then start dropping to 2800, and back to 3000. At this point I decided to get it back on the trailer while it was running. It ran fine as I power loaded it back on.

I stopped on the way home and added 10 gallons of fresh premium and when I got home added Sta-Bil Marine. I hooked up the water hose and started the motor to let it idle to see if that fixed the issue. It ran normally for about 20 minutes, then started to idle rough and stall. If I started it again, it ran fine for about 30 seconds, then idled rough and stalled.

Could it be as simple as bad gas? The fact that it runs fine sometimes doesn’t sound like that is the issue, but I am no mechanic.

Thanks for your help,
Bart

[Cycleman07]

Sounds like you might have an over heating problem. Wondering if you need to check the impeller.

[BartMan]

Thanks for the response cycleman. I have a water pressure gauge that showed normal psi for all RPMs, and plenty of water coming out of "pee" hole. I actually felt the water coming out of it when I had the hose hooked up -- it was warm as I expected, but not overly hot. I also think I read that the motor should alarm if overheated? I just had the impeller replaced 55 hours ago during the first 100 hour service. Having said all this, I will check it the impeller if no one else comes up with any other ideas.

[cwag911]

You might want to have the dealer hook it up to their computer and check for trouble codes.

[Cycleman07]

The impeller may be good but there could be something blocking the inlet. Had this happen on a pontoon i was on. It was a plastic ice bag that got sucked up in it.

[lakerunner]

Did you check your primer bulb?

[Waterlogged]

Sounds similar to my 115 4stk when it was new. Fuel line or lines broke down. It ran somewhat like yours then quit. Entire engine, lower unit and oil system were filled with gasoline. It took a major teardown to clean everything out. Just over a year old, work covered by Mercury under service bulletin.

Glenn

[BartMan]

Thanks all for the ideas. I decided to take it in after verifying the motor is still under warranty. I will post here the results in case others experience these issues.

Lakerunner: No primer bulb on my fuel line...built in tank with 7 foot of line.
Cycleman: I suppose that is possible, but wouldn't the water pressure not be as high if it wasn't getting enough water?
Cwag911: I am taking it in tomorrow, but they said they won't get to it until early next week.
Waterlogged: I always use Sta-Bil Marine which supposedly negates the damage that can be caused by ethanol, but who knows, hopefully whatever is causing this is minor.

Again, thanks all for taking the time to respond. Bart

[Waterlogged]

It wasn't ethanol damage on mine, it was defective parts that they were aware of.

Glenn

[robbrown27]

I'm currently going through a similar prob with my 2006 merc 115, had both fuel filters and impeller replaced last week. Ran great at the shop for the tech and we took it out Friday, rode about 45 mins ran like a scalded dog at all rPM's. Parked for a couple hours and wouldn't run above 2000 rPM's then just violently died, towed back to dock and ran fine to load, almost! Came a few feet short, repeat issue. I took it to the shop again. There were no codes in the computer last time, no alarms either time. I researched a little last night and I believe it is in the fuel control. The Merc uses a lift pump to fill a sump, switch senses full and stops pumping, fuel pump operates with fuel in sump, as level drops lift pump cycles again to fill sump, repeat etc. Merc had an issue with a fuel line that is inside that fuel sump/control/panel whatever they call it. Google "BBC boards" that is where I found some info, also good info on this page: http://www.justanswer.com/boat/7o0om-20 ... -want.html; sounds like a good answer. Not an O/B expert but if my boat wasn't 115 miles away it is where I would be looking!? Also I read, you can add a fuel primer bulb to help troubleshoot similar problems. If it runs when you pump bulb to hard there is a high probability with your fuel pumps or float sensor in the sump? Just my free lessons from the last 2 nights of reading, my mechanic says he has never had to change a fuel pump on a Merc 4stroke? So the sensor and wiring play into that also?

Let us know what the end problem is, I wil, do the same.

[Waterlogged]

I had to replace a fuel pump on mine. Separate problem from what I posted above. Some part of the pump rusted from water brought in by ethanol.

Glenn

[dunny961]

I'm currently going through a similar prob with my 2006 merc 115, had both fuel filters and impeller replaced last week. Ran great at the shop for the tech and we took it out Friday, rode about 45 mins ran like a scalded dog at all rPM's. Parked for a couple hours and wouldn't run above 2000 rPM's then just violently died, towed back to dock and ran fine to load, almost! Came a few feet short, repeat issue. I took it to the shop again. There were no codes in the computer last time, no alarms either time. I researched a little last night and I believe it is in the fuel control. The Merc uses a lift pump to fill a sump, switch senses full and stops pumping, fuel pump operates with fuel in sump, as level drops lift pump cycles again to fill sump, repeat etc. Merc had an issue with a fuel line that is inside that fuel sump/control/panel whatever they call it. Google "BBC boards" that is where I found some info, also good info on this page: http://www.justanswer.com/boat/7o0om-20 ... -want.html; sounds like a good answer. Not an O/B expert but if my boat wasn't 115 miles away it is where I would be looking!? Also I read, you can add a fuel primer bulb to help troubleshoot similar problems. If it runs when you pump bulb to hard there is a high probability with your fuel pumps or float sensor in the sump? Just my free lessons from the last 2 nights of reading, my mechanic says he has never had to change a fuel pump on a Merc 4stroke? So the sensor and wiring play into that also?

Let us know what the end problem is, I wil, do the same.

My 2011 90hp Merc had the issue with the fuel float sensor. It would run fine until it got hot. After that, good luck trying to start it. Took it to a dealer and theyb replaced the sensor. No more problems. The sensor had a recall on it with the Verado engines. It's the same part # on the four strokes. I guess Mercury had to take care of the Verado line, but left the 4 strokers to fend for themselves.

[tommyz]

I too had similar stalling problems, and it was the float in the fuel pump. Replaced pump under warranty, been fine ever since.

[robbrown27]

Just called to check on my boat, they said the lift pump is bad? Hopefully we can get on the water Wednesday? I'm leaning forward the float sensor, it sounds fairly rare for the lift pump to go bad. I'll pass on the outcome, hopefully this week. It's gonna be tough being at the lake with no ride!

[Soonertoon]

My 90 Merc quit on me 5 times in 5 trips to the lake. Same symptoms more or less. I finally fixed it .....I traded the piece of shit off today.