So I have 2 8.1 HO engines (from 2014) in my boat with 200 hours.

Port side. I changed plugs and they seemed pretty rich looking. Engine runs perfect though. I thought my fuel gauge was off all of this time but now I realize the port side burns maybe 15% more fuel than the starboard side. I have all new fuel lines and filters. No leaks anywhere. I am about to change spark plug wires. What else should I check? I think fuel is being wasted somehow. Would the fuel cool system cause this?

Starboard side.
I had a lot of missing at mid-high RPM & the boat would shake even at low rpm. Turns out it was a spark plug that was cracked and the wire was totally OFF. I changed all spark plugs and no more bad shake. It runs way smoother now. BUT, at over 3600 RPM I get a small popping sound so there's still a misfire. I can tell the engine isn't as smooth as the other. I am about to change all spark plug wires on this one too. I'm wondering if a misfire is bad for the engine if I run it? (want to go out this weekend) and if changing the plugs and wires doesn't fix it, would the next step be the coil being bad? (the coil where the spark plug wire was off). I'm tempted to buy the Rinda engine code reader although I do have vessel view. Vessel view shows no error codes though! And it won't show any misfire info.

At anything under 3600 rpm the engine seems perfect and I never go that high in RPM but I was testing some stuff so I cranked it up one day and found it misfiring.

thanks for any help

I'm not sure if you have the paint issue with the cool fuel units on 2014 motors. But burning more fuel than you expect is a tell tale sign that you have a pressure problem on that port motor. See what the rail pressure is and pull the fuel regulator, the screen could be clogged up with paint.

Ive read about the paint issue for the gen 3 and not sure if mine is like that either. I did buy new filters for the cooler and need to put them in. I need to figure out where the regulator is also. I bet that screen is clogged!

You need access to a scanner with those motors. The motor has 8 coils, and while one might have an issue, we need to do some testing before replacing anything. If parts are replaced without testing, it can cause other issues to show up.

The misfire at higher RPM's could be many things, plug, wire, coil, injector, valve, preignition from a lean condition

Burning more fuel could be a few things, MAP for one, and a scanner will tell if the output is off

ok I think I'll just buy the Rinda scanner. One thing to note, the engines ran full throttle fine when I bought it (maybe 10 engine hours ago) but we changed out risers and manifolds causing that plug to crack. (weight of the manifold resting on plugs during install) which is why I switched them all out. I was getting a Beep which led me to find the spark plug wire crack and wire was off. I replaced that plug and no more beep. Engine runs better. But I THINK ... this caused another issue or a plug wire was pinched. Maybe the wire being off arched or something. So the next obvious step is to replace all spark plug wires.

That's where I am now. So its possible that one coil went bad from a spark plug wire hanging down. I don't think its anything else since this all happened in like 2 months time.
I will find out this weekend on that one. I have all new wires ready to go.

For the other one, with fuel issue, I'm trying to figure out where this regulator "screen" is. I see the exploded view but there is no screen. I know there are 2 fuel filters in the fuel cooler. Is this the thing I need to check? I actually have 2 brand new sets of these because I planned on changing them.

What is the motor serial number?
Need to look up its configuration

It is 1G300338

Comes up as a Merc reman, all good

If your looking for a screen like was used on the earlier Regs on the fuel cooler tube, this model doesn't use one like that.
https://www.mercruiserparts.com/bam/...32022/16439/60

Not having the problem before riser changes, you could be right on wires and plugs. Still I wouldn't change a coil out unless it can be determined which one(s)

ok, thanks for all of the help so far!
I mentioned screen because the other person responded that the engine may be getting too much fuel and screen may be clogged. So if there is no screen, what do you suggest I look for if engines are running rich and it seems to use 10-15% more fuel than the other side? I guess the regulator could be bad and I should test fuel pressure. Other than that, not sure what would cause it.

Would an engine scanner check for fuel pressure? I'm assuming no.