Motor sporadically shaking/ sputtering

[JPascavage52]

I have a 50 hp Mercury 4 stroke EFI outboard on my Bass Tracker. Today, headed out and drove around the lake a bit trying to decide where to fish. After idling around awhile, checking out some brushpiles, rock humps, and offshore structure on my sidevu, and marking gps points, I decided to head up a nearby spawning flat and fish it. Out of nowhere, the motor started shaking and making a sputtering noise. Everything else was fine, engine was peeing, not shutting off, and would start right back up if I turned it off. I could increase throttle, and the boat would start to get on plane, but it was very shaky, sort of like a stick shift vehicle trying to stall. Initially thought something may have gotten caught in the prop, but nothing was. Not wanting to cause any damage, or get stranded, I decided to start crawling my way back to the dock. However, after a few minutes of running slowly, the shaking and sputtering noise stopped, and everything went right back to normal. I ended up running back up lake to the spot I was going to fish with no problems. Caught two right off the bat, then the wind picked up and shut them down completely, only had one other bite. Ran across the lake to check out a small cove, after idling around it a bit, I was about to head to another spot when the shaking and sputtering once again started. At this point, I once again started crawling back to the dock, and sure enough, once again, the shaking and sputtering stopped a few minutes later. This time, I ran back to the dock, since it was getting late, and the fishing was slow anyway. 

Any ideas here? I've been googling it all since I got home, and the indications are water in the gasoline or a blockage in the fuel filter, although today was the tenth day I've been out on the boat this year, including all day yesterday, without any issues. 

 

[Team9nine]

I'm not a mechanic, so I can't say for sure. What I can tell you is that every time I have any kind of engine problems that might be related to gas, carbs, throttle, etc. I always start with a full can of SeaFoam ran through the fuel and engine, and sometimes a second can. Stuff cleans up and fixes much of the small stuff that affects engines 

[IndianaFinesse]

Not a mechanic by any means, but I just got through fixing every conceivable thing on my motor, one of which was similar to what you described.  If I had to guess, there's something partially clogging the fuel pump and/or carburetors.  Had some metal shavings (all motors have tiny bits of metal worn away over time) and tiny pieces of plastic clogging the fuel pump and the carburetors.  The fuel pump problem was solved when we replaced it after our starter blowing up and taking g the top off of the fuel pump, and we had to rebuild and clean the carburetors to get the junk out. 

[DogBone_384]

S the motor injected or carbeurated? If it's carb'd I'd drain and remove the bowl to see what the gas looks like and if there's any crud in the bottom of the bowl.

 

How old is the gas, and do you use Seafoam or Stabil?

 

Other than that, check your battery/electrical connections, making sure they're clean and tight.

 

Good luck with it.

[Clinton john]

Sounds like water are trash in the gas.

 

If you have a fuel filter are water separator you need to pull them and clean them good.

 

If the gas is old dump it and refill the tank and put in some good additives to clean the fuel s yestem and reduce or remove water from the fuel.

 

Won't hurt to check and see if the plugs need to be changed.

 

Google nonethanol gas and only run that in your motor, ethanol gas is the devil when it comes to outboards, even more so if you leave fuel in the motor and fuel line and let the boat sit for more then a week.

 

Hope this helps sir.

[JPascavage52]

It is an electronic fuel injected motor. I keep the boat stored in my garage during the winter, with a full tank of gas and some Stabill, and I usually run a can of Seafoam through it on the first time out of the year. It has started right up and ran fine every other time out this year. So, I am doubting that it has anything to do with the gas that was stored in the boat. It does not have a fuel/ water separator, but simply has an in line cartridge fuel filter, identical to this: https://www.walmart.com/ip/Mercury-Mercruiser-35-879884T-Mercury-Quicksilver-W9-Fuel-Filter-Outboard/32742619?wmlspartner=wlpa&selectedSellerId=9584&adid=22222222227021901188&wl0=&wl1=g&wl2=c&wl3=51775951151&wl4=pla-89208267659&wl5=9006507&wl6=&wl7=&wl8=&wl9=pla&wl10=115791965&wl11=online&wl12=32742619&wl13=&veh=sem
Also, I still have the rubber gray fuel line that came with the boat, I know this is bad, and it is something I have been planning to replace, just haven't gotten around to it. 

I had a little less than half a tank of gas in the boat at the time it started, the last time I filled up was last Sunday. I am wondering if 1) This weekend, it was windy and rough on the lakes, and I took several waves/ backwashes over the stern. I am wondering if some water got in that way, I've heard of that happening a few times in rough conditions with a vented cap, or even with people who forget to put the drain plug in. 2) I got a bad batch of gas when I filled up last time, or what the last of what was in the tank at the gas pump. 3) I have some contaminants in fuel system/ filter/ line that are blocking things up.

I am going to take a sample of the gas that is in there tonight and let it sit for a bit and see if there is any sludge settling at the bottom, or any particles or anything floating around. Probably going to clean/ replace the fuel filter, replace the gas, run some dry gas/ seafoam through the tank, and see what happens. 

[Clinton john]

Get a clear glass and take your fuel line off the motor then insert aflat nose screw driver in the fuel connection that way it is open like if it was attached to the motor, then pump on the fuel bulb and it will pump fuel out and into the glass fill it to half full and stop.

 

If the fuel comes out a ugly white murky color you have water in your fuel, if not let it set in the glass till it calms down then look for trash in it.

 

Stabil is the last thing I would use in my fuel, been there tryed that got tired of replacing spark plugs every motor I tried it in started smoking bad after I put that stuff in it.

 

If your running ethanol gas more then likely you have water in the system, ethanol gas makes water bad, either from sitting in the boats gas tank or from sitting in the tank at the gas station.

 

I hope you get it figured out sir

[JPascavage52]

Welp I took the fuel filter off and siphoned a bit of fuel into a mason jar. Let it sit for awhile, there are a few brown and black particles on the bottom, but no layers of sludge or separation. I banged the fuel filter off to get some dirt/ particles out, a few came out but not a lot. Guessing the problem is a bit further in the engine. I bought a couple cans of Seafoam, and I'm going to try to run some through to see if I can clean/ burn off/ dissolve any garbage that may be doing this. 

[WRB]

First thing to do is check your spark plugs, they should be gray/tan color not black. Change them if you haven't already. Change to a new fuel line and prime bulb. Change the fuel filter. If that doesn't clear it up you need to get it professionally serviced.

Tom

[JPascavage52]

Welp, last week, replaced the fuel filter, fuel line is good, added some seafoam, and as a precaution, filled her up with fresh, ethanol free fuel. I gave the plugs and all electrical connections a quick check, everything looked fine to me, but didn't replace them. Started it up and it ran fine in the driveway, then took it to a local lake last Tuesday to fish a bit and see if the problem was corrected. It ran fine, everything from wide open throttle to idle, so I figured the issue was behind me, maybe whatever was blocking/ gumming everything up had cleared up or had been burnt off by the Seafoam. Decided to go ahead with the trip to Presque Isle my gf and I had planned for the weekend. Saturday, we fished all day, despite the bay being a bit rough, boat ran fine with no issues. This only made me more confident that everything was hunky dory and okay. Sure enough, we went out again Sunday, ran out to our first spot WOT, no problem, and started idling around looking for a hump I had found last year, when the shaking/ sputtering once again began. Fortunately we weren't that far from where we launched, so I decided to shut it down and fish for a bit, thinking we could always crawl/ use the trolling motor to get back if worse came to worse. After catching a couple, we decided to move to a nearby spot. Motor started up fine, engine sounded normal, and we moved to the new spot no problem. Had no luck there, so decided to move again. Started up fine, we ran to the new spot no problem, and then, after a few moments of idling, the shaking/ sputtering again began, and this time, it didn't go back to normal. At this point, I was aggravated by the slow fishing, the wind, waves, and rain picking up, a major backlash in one of my reels, and the motor issues, so we decided to crawl back to the ramp and call it a day. 

There is a marina at the boat launch we used, and we briefly talked to a guy there about it, he said it sounds like the plugs are getting flooded, so I will likely change them next. I am just puzzled as to why this only happens after a day of running just fine. 

[WRB]

Check your power packs, sounds like they are about to go bad. Definately change your plugs, cheap and easy to do. You may also have debris in your gas tank, check the new clean filters.

Tom

 

[JPascavage52]

Last night, I pulled the boots off all the plugs, in order to see what part I need. I notice that the plugs are covered in some sort of bright yellow paste. 

[WRB]

The ceramic outside of the plug or the inside electrode?

The outside could be a dielectric coating to prevent corrosion. Do you have a engine manual that list what plugs you should be using? This tells me you haven't changed your spark plugs before this!

Tom

[Fishing Rhino]

I'm going to suggest you try something simple.  

 

The next time it acts up, try squeezing the primer bulb.  From time to time this happens on my 200 hp Merc and I have seen it happen to a friends 250 Merc.  The first time it happened to me was on take off.  The boat was about on plane when the engine sputtered.  I pulled the throttle back, let the motor idle a bit, then it took off fine.

 

Now, when I'm going through my preparations prior to heading out, I make squeezing the primer bulb part of my routine.  Some times it's fine.  But at other times I have to squeeze the bulb five or six times before it's fully primed.

 

The tech told me that changing the check valves in the fuel line will not always solve the problem.  Part of it is because the primer bulb is at about a forty five degree angle and the fuel can gradually drain back into the tank.  

[JPascavage52]

For reference sakes i took a video of the what is going on, although I just now figured out how to  cut it down enough to post.

20170521_122107_001_002.mp4

And this is what one of the plugs i have sitting here looks like.. although each one is very similar to this

[JPascavage52]

Welp, I just finished changing the plugs a few minutes ago. Started the motor in the driveway, and kept the cover off to check for anything sounding unusual. Noticed it started up with a bunch more "uumph" than it usually does. The sputtering/ shaking was present for about a minute, then stopped. Going to try to get on the lake tomorrow, so well see. 

[JPascavage52]

Welp, sorry to resurrect this old thread and be a pain, but I'm stumped again. With new plugs, new fuel line, new fuel filter, and new gas, boat ran fine without the issue for the past month, including our two day club tournament at Mosquito Lake, OH, which I took third, and my GF and I's two day trip to Lake Erie, along with I'm guessing a good five or six other days on the water since. Thought the problem was behind me. 

Sure enough, got to our third tournament of the season on Saturday, backed off the trailer and as soon as I started it up, the same thing came back again. It only did this for a few seconds, and as I headed out of the cove, I saw no signs of it doing this again, so I decided to make my run down lake. Everything was fine all tournament except for struggling to catch fish. Then sure enough, headed back at weigh in time, and about a few hundred yards from the launch, while I was BSing with some of the other boats about how bad the fishing was, it started doing the same thing again.

I'm taking it to the shop next week, would rather figure out what's going on once and for all and fix the problem permanently, than continue to throw money/ parts at it. 

 

[JPascavage52]

Welp we figured it out, ended up being the ignition coil on the third cylinder was on its way out, was shorting and cutting in and out, getting hotter every time. Was introduced to a mechanic through a friend of a friend, and he came out with me one night last week and had me run the boat till the issue started, then he told me to pull up the cowling, and start disconnecting the little 5-pin plugs on the back of each coil, listening for the sound of the motor to change, and the rpm/ power to drop. The first two had quite an effect, but the third had no effect at all, he immediately stopped me and said "yep, this is your culprit right here." Got a replacement coil, and installed it, have had it out twice with no issues. 

Thanks to all for your help!