Low power, Broken spark plug

Merc would list an iridium plug for that 2007 engine.
The mr43t isn't iridium.
Consult your manual or call Merc's customer service.
 
scoflaw said:
Merc would list an iridium plug for that 2007 engine.
The mr43t isn't iridium.
Consult your manual or call Merc's customer service.
Click to expand...

It might be even easier to look up the engine serial number for the correct plugs.

While chasing the correct plugs is a reasonable thing to do......the plugs you removed have been in that engine a very long time.
 
OP says he replaced them 2 years ago.
Merc regularly supersedes plug numbers as the years go on.
 
scoflaw said:
OP says he replaced them 2 years ago.
Merc regularly supersedes plug numbers as the years go on.
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I agree with you but something isn't right with this story. Do those look like two year old plugs to you?
 
I appreciate the reply so far, I did scope the cylinder of the 1st plug and here are some pics, I don't really know what I'm looking for but it doesn't look that bad to me.
 

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Were you poking around in there with something sharp? Looks like there is a couple scrapes on the piston in the first picture.
Probably time to bring someone in to help you with this. Proper diagnoses while tearing things apart can save you from doing twice.
 
I was not in there with anything at all except the camera lens. I did check the distributor and rotor. They looked clean. I did notice that the rotor cap, the plastic cap that spins in the distributor, although the screws are tight, does have a little bit of play where I can twist it back and forth approx 2-3 degrees each way. I don't know if that is acceptable or could that be an issue with the timing? The engine seems to run like a champ under throttle, but idling is where I can feel it shaking a bit.
 
emckissack@hotmail.com said:
I was not in there with anything at all except the camera lens. I did check the distributor and rotor. They looked clean. I did notice that the rotor cap, the plastic cap that spins in the distributor, although the screws are tight, does have a little bit of play where I can twist it back and forth approx 2-3 degrees each way. I don't know if that is acceptable or could that be an issue with the timing? The engine seems to run like a champ under throttle, but idling is where I can feel it shaking a bit.
Click to expand...

That twisting would be the mechanical advance In the distributor. It’s normal.
 
Although I am not a boat technician, I am an ASE Master tech that does work on engines. I would have to agree with all the above posts, you have a lean fuel mixture for some reason that needs to be diaged. The pistons are starting to melt away due to pre ignition. The pieces of the plugs that are missing have melted away! This is not a job for the "do it your selfer" IMHO.
 
Espos4 said:
That twisting would be the mechanical advance In the distributor. It’s normal.[/QUOTEI doubt
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There shouldn't be a mechanical advance on his engine. 2-3 degrees would be normal in gear lash though.
 
emckissack@hotmail.com said:
Also, I checked on the plugs and I have compatible plugs according to the manual.
Click to expand...
Well...that answers one question.
Now, why are those things getting torched like that? I still think you need a good mechanic on this one.
You should definitely be involved and know exactly what the problem is. But trying and experimenting until you eventually get it could be fatal to the motor.
Good luck to you. For my education, please keep posting updates on your mystery.
 
Just guessing here. But I know my buddy pulled his injectors off and had them tested, cleaned and then reinstalled.

after that, the cool fuel module would be my next guess.... I agree, might be a good time to hire a mechanic that knows these motors before you do more damage
 
You are getting some very good, experienced help here. I would strongly suggest you listen to it. If not, you will be replacing that engine, probably sooner than later. No offense, but from your contributions, your mechanical/engine experience is limited. I appreciate your being proactive and trying. But this has escalated past the proverbial shade tree mechanic. I totally understand the financial impact of this, hence your asking about fuel additive/using premium fuel to resolve. But these are only bandaids at best. Kicking the proverbial can down the road. Spend a little now, or a LOT later. And you can still capture most of the boating season(if there will even be one this year!) if you deal with it now. Good luck.
 
Would think check the fuel pressure at idle and WOT, change fuel filter as well. If pressure is low that points in one direction if pressure is ok have injectors cleaned and flow tested.

agreed that marks on piston top are pistons being beat to death by detonation
 
All things I hate to hear but maybe the best thing I can do is take it to someone to check out. I was hoping it wasn't as bad as sound like it is. Ill ket this updated as I have more info, maybe several weeks before I can get it to the shop though.
 
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