2012 Mercury has occasional shudder when just in gear

[Cottage_guy]

I have a 2012 60 HP Mercury Bigfoot EFI model 1A60453BZ that has a mysterious shudder/stutter/misfire when just in gear. It is intermittent, might last for 2 - 3 seconds and might happen every minute or so, or might be several minutes apart. Here's how I can best describe it: imagine biting into something bitter, you know that quick shudder you get? That's what it's like. It does not stall out, is not hard to start either hot, cold or in between. It was bought new and even now has less than 300 hours on it. Have been doing all the regular maintenance on it. Recently changed out the sparkplugs even though they looked totally fine and spark is strong, replaced both fuel filters (they looked fine too) and changed out the fuel and tank, timing belt while not changed doesn't show any wear. Have always run ethanol free fuel with Seafoam stabilizer. Its hooked up to the VesselView engine monitoring system and no fault codes are reported. No misfires at any other speeds, no bogging on acceleration, in fact if I simply nudge the throttle a little bit it's totally fine and it doesn't do it in neutral and I don't recall it doing it in slow reverse. Unfortunately I can't recall the RPM (pretty sure below 1000) but I know that it didn't fluctuate very much when this happens , maybe 10 or 20. The idle speed is controlled by the ECM and is not adjustable apparently. If this was normal I guess I could live with it but I have a neighbour with the exact motor and his does not have this issue and can troll quite nicely and slower than I can and he's not using a trolling plate, we both have these on pontoon boats. This is my first post, hope I did it right and gave enough info.

 

[QBhoy]

Could it be to do with the prop and hub kit ? Just with having the larger gearbox than the normal engine, she should run the larger props and a better hub kit. Often these and the CT later models can suffer prop rattle. There is now a hub kit available that deals with that.

 

[Cottage_guy]

Could it be to do with the prop and hub kit ? Just with having the larger gearbox than the normal engine, she should run the larger props and a better hub kit. Often these and the CT later models can suffer prop rattle. There is now a hub kit available that deals with that.

Thanks, that's something to check but the motor came new with the prop and either the Flo Torq II or III, I cant really recall. When I took it off this winter to grease the splines it looked fine, no wear, nothing. I'd like to think the dealer gave me the right stuff and I'm pretty sure if it was doing this shudder thing right after I bought it I would have been back to the dealer. I really cant recall exactly when it started this but I wanna say the last two years.

 

[QBhoy]

Thanks, that's something to check but the motor came new with the prop and either the Flo Torq II or III, I cant really recall. When I took it off this winter to grease the splines it looked fine, no wear, nothing. I'd like to think the dealer gave me the right stuff and I'm pretty sure if it was doing this shudder thing right after I bought it I would have been back to the dealer. I really cant recall exactly when it started this but I wanna say the last two years.

Ok. Not to say it couldn’t be fuel related perhaps. Or sensor related. I’m not certain that many folk know about the newer hub kit that reduces this, if it is at all this in the first place. Lots of potential reasons for such a thing really. Slightly damaged prop would be one. Bad fuel or even the slightest reduction in flow to or from the pump or vst tank. There is an injector pre filter that many forget about too. Right before the injectors.

 

[Chris1956]

My old Evinrude did that. Of course, it was a Frankenrude, with the wrong carb on it. I therefore think it is a fuel related miss.

What kind of motor is it? 2 Stroke EFI? Maybe the fuel injector needs adjustment or the injectors are clogged? I would unplug and clean all electrical cables on the motor. Maybe you have some corrosion.

Just a SWAG.

 

[Cottage_guy]

Ok. Not to say it couldn’t be fuel related perhaps. Or sensor related. I’m not certain that many folk know about the newer hub kit that reduces this, if it is at all this in the first place. Lots of potential reasons for such a thing really. Slightly damaged prop would be one. Bad fuel or even the slightest reduction in flow to or from the pump or vst tank. There is an injector pre filter that many forget about too. Right before the injectors.

Fuel is fresh ethanol free and then treated with seafoam if its going to sit for any extended time, the tanks and fuel line have been swapped out to and checked for leakage and blockage. The prop is pristine, I can honestly say it has never even touched sand. I will check for any issues from the pump. The pre-filter you mention, is that the one they buried in the bottom of the lower cowling? If so, its been swapped out two (but was clean). Wondering if id might be the VST or maybe a funky injector.

 

[Cottage_guy]

My old Evinrude did that. Of course, it was a Frankenrude, with the wrong carb on it. I therefore think it is a fuel related miss.

What kind of motor is it? 2 Stroke EFI? Maybe the fuel injector needs adjustment or the injectors are clogged? I would unplug and clean all electrical cables on the motor. Maybe you have some corrosion.

Just a SWAG.

4 stroke efi, I did disconnected all the wiring harness and while I didnt see and corrosion I still put some dielectric grease on them. I was hoping to stay away from the injectors and vst since the filters were so clean but maybe I'll take a look. I'm still a month away from launch, just want to gather as much intel beforehand. thanks

 

[QBhoy]

Fuel is fresh ethanol free and then treated with seafoam if its going to sit for any extended time, the tanks and fuel line have been swapped out to and checked for leakage and blockage. The prop is pristine, I can honestly say it has never even touched sand. I will check for any issues from the pump. The pre-filter you mention, is that the one they buried in the bottom of the lower cowling? If so, its been swapped out two (but was clean). Wondering if id might be the VST or maybe a funky injector.

There is usually a filter in the end of the fuel injection rail. Wee insert type arrangement. Think it’s to be changed or at least cleaned/inspected every 300 hours.