2004 Optimax 150 intermittent miss under load

[caseyshoe27]

04 Optimax 150 #1-150D730

Took the boat out after being at a Mercury certified mechanic bc it was sitting for a couple years before purchasing it. Cranks and idles fine. Idled out and when I went to take off and it misses/stalls. Ease off the throttle and it will pick back up and plane out and sputter a few times while on plane. There is no particular RPM when it will bog/miss or for how long but it seems to be pretty consistent when you hammer down to WOT. It is like a split second of a stall then RPMS go back.

Pulled it home and checked the plugs. 1 of the 6 was a COMPLETELY DIFFERENT PLUG! (5)NGK IR IZFR5G and (1) NGK R ZFR5-11
Ordered 6 of the OEM plugs to go back in it. Before I put the plugs back in it and run to the lake is there anything else I should check? Would that one plug cause my issue?

Mechanic fixed the following
-Drained/Cleaned fuel tank
-New cranking battery
-All new fuel pumps and filter
-All new fuel lines
-Changed oil reservoir (Had 4 beeps) sensor was bad
-New waterpump
-Neutral switch wire was pinched
-Diagnostics showed no other faults other than the oil reservoir tank.

[lpugh]

yes it could!

[lpugh]

Mist down the plug wire and coil to see if that causes misfire or a visual spark leak
Use a KV tester to test coils available voltage, should bridge a.500 air gap without breaking down.

[SilverFox579]

How a reputable mechanic could miss that is beyond me. Makes me wonder if they even bothered to check plug gap.

[TomP.]

How a reputable mechanic could miss that is beyond me. Makes me wonder if they even bothered to check plug gap.

Was kind of curious myself along with replacing all the fuel pumps that bill alone would be around $1,800

[JOE54]

yes it could!

definitely , and dont get me started on how it can be missed ,,,, one example had a customer call me serveral months ago had xr6 with bad cyl in it didnt want to wait for me to replace powerhead soooo he calls shop x they replace powerhead this is a late model cdm engine mind you they keep it for months man calls me agian says hes done with shop x they cant make it run ask why he states engine will start but has no power " did you pay for repair "yes alot brings boat in i pull cowling just to take a look trigger is plugged in to wrong harness wire colors dont even match he lake tests it runs great , took all of 5 minutes "that wont happen again" he says , seats and gel on boat are ruined by the way

[SilverFox579]

There's a reason I do all my own maintenance. Other than me, there's only one where I live that I let touch my engine.

[caseyshoe27]

Update: new plugs and she’s back to business! Running like a scalded dog.🤙🏼

And yes I was surprised the spark plugs were never checked. Live and learn. I guess everyone has an off day.

[JOE54]

There's a reason I do all my own maintenance. Other than me, there's only one where I live that I let touch my engine.

dont blame you one bit FOX