Mercury 115 low rpm misfire

[ryanb]

My port side 115 (twins) seems to be having intermittent misfires at low rpm (trolling, idle). It's brand new with only 12 hours. Dealer replaced the spark plugs under warranty and called it good. Which it obviously wasn't, happened immediately again upon hitting the water. Anyone have any thoughts what it might be? Doesn't happen at all at higher planing speeds.

 

[fishin solo]

Check the coils

 

[ryanb]

Check the coils

Would that only cause low rpm problems though? Motor runs perfectly above 2500 rpm.

 

[fishin solo]

Is it misfire or more of a shuddering noise ? Maybe @SteelyDan can chime in about the coils

 

[ryanb]

Engine shudders, rpms drop. Seems to be like a cylinder is dropping for whatever reason. Booked back in at the dealer, but just more waiting. Under warranty or not I like to fix my own problems when I can.

 

[kingblazer84]

Engine shudders, rpms drop. Seems to be like a cylinder is dropping for whatever reason. Booked back in at the dealer, but just more waiting. Under warranty or not I like to fix my own problems when I can.

Maybe an injector is having a problem as well but testing the ignition system is the first step, typical dealer though flat rate guys love no fault founds and just toss a basic item at it and send it out the door!

 

[wildmanyeah]

A new engine with 12 hours you’d best put up a big stink about it now.

Kinda sucks because of the time of year but you should really go balistic on them.

you spent lots of money should not have to deal with anything like that. I would want assurances that the motor is perfect or they can replace with brand new.

 

[ryanb]

A new engine with 12 hours you’d best put up a big stink about it now.

Kinda sucks because of the time of year but you should really go balistic on them.

you spent lots of money should not have to deal with anything like that. I would want assurances that the motor is perfect or they can replace with brand new.

Yep, but as with so many things now a days, boats and otherwise, they just shrug and say it's covid. Can't find a new 115 anywhere right now, so demanding a new engine isn't likely to get me anywhere.

 

[Bryan Allen]

I had my 115 merc powerhead replaced on warrantee last month. Took 3 weeks to get one from the US as there was nothing in Canada. Just a suggestion-- dont try to fix it yourself. That gives Mercury an out on honoring its warrantee

 

[salmonkiller01]

If you have it running disconnect coil wires one by one. The one you unplugg and doesn’t make a change to idle is the culprit.