2009 Optimax 225 - Surging, Rough Idle and Loss of Power

[Twokids]

2009 Mercury Optimax 225 (Non-DTS)
Serial #: 1B752624


Motor has run flawless for 5 years I’ve owned it. Always run ethanol free and quikleen. Boat gets used 1-2 times per week so gas stays fresh. Estimated 500 hours on motor.


Went to get on plane and was barely able to, with surging between 3000-3500 rpm, noticeable lack of power, WOT was only about 4500. Turned around and headed back, it started to clear up and ran clean for a couple minutes then it just got progressively worse over a 30 minute period. Eventually I was unable to get back on plane, surging at various rpms. Two hour ride back to ramp unable to exceed 5 mph. While troubleshooting today on the muffs, Idle is very rough and stalls in less than a minute. Restarts and repeats.


Due to the progressive nature of the degradation over time it doesn’t seem like I was down a cylinder due to a plug or coil issue. The magnitude of the power loss made it feel like it was running on less than half the cylinders. To me it seemed like a fuel system issue that kept getting worse.


Things I’ve checked:
Drained VST, fuel was clean, no debris, no water.
Fuel filter in VST clean, less than year old.
Plugs and plug wires looked good.
Primer ball stays firm pre-start, running and after shutdown.
No alarms or overheat conditions.
Compressor sounds normal.
Battery new and exceeds min specs.
Purged Schrader valve on port fuel rail and noticed a slight smell of fuel in mist.
Removed and inspected tracker valve. Looked good.
Rebuilt the pulse pump with new diaphragm kit. Old diaphragms in good condition.
Hooked up gauges to test air/fuel pressures:
At idle=Air 80psi/Fuel 92psi
5 sec after shutdown=Air 80/Fuel 86
10 sec after shutdown=Air 80/Fuel 81
15 sec after shutdown=Air 80/Fuel 78


Performed Air Compressor and Fuel Pump Volume Test per the pub. Pinched air discharge hose and air pressure rose quickly as expected. Pinched fuel return hose and fuel pressure rose as expected.


Performed Fuel Injector Leak Test per the pub. Turned key to “on” without starting. Pressure peaked at 72psi while fuel pumps were running (pub says should peak 40-45psi). After the pumps stopped running the fuel pressure bled down about 2psi per second. Have not performed the rest of fuel injector leak test where you remove the rails. Not sure why peak value was so much higher than pub says it should be.


Have not checked compression yet, on the agenda for tomorrow.


Recent motor history:
Removed powerhead a month ago to replace motor mounts and swivel pin bushings. Reinstalled using OEM parts from Don’s shop and everything torqued to specs. Motor ran great for weeks prior to current problem. Boat is a 2004 Triton TR-21X with what looks like original fuel lines, parts on order to replace from tank to motor. Motor has analog gauges, smartcraft on order from European Marine.


Sorry for the long data dump but I’m hoping there is something here that will help to get ideas from the BBC brain trust.


Thanks in advance for your time.

[EuropeanAM]

That's a LONG read. Let's back up and check the BASICS:

-Compression Test

-SPARK TEST.

Your air/fuel pressure tests are relatively normal.

[Kb444fishing]

My 08 was doing about the same switched almost everything finally my mechanic switched all fuel system rails etc with another bunch he had. Running like brand new. Sending them in to be cleaned. Have 600 hours don says around 400 to be serviced.

[Twokids]

KB - Thx

Don - Good spark on 1-6

Compression #s:
1=94
2=95
3=106
4=101
5=96
6=102

Plugs are now getting fouled up in a hurry. In fact two had soot built up between between the electrodes. I cleaned them up prior to compression check warmup and it is idling much better. Any idea what is causing the rich condition? Sounds like I am over due for injector service...

[EuropeanAM]

Which plugs were fouled (specifically) so badly that it was bridging the gap?

CHANGE that fuel filter. Have seen way higher incidence of plugged/restricted filters this year (some less than 2 months old).

[Savage]

Better check the thermostats and make sure the motor comes up to 120*-130*F at idle.

[Twokids]

Don - Will get that fuel filter replaced right after I replace my fuel lines. Parts on the way.

Bridged gaps in 1 and 5, 4 was getting there. This was after a 3 hour limp back to dock and 30 min of troubleshooting on the muffs.

75E4FB15-2219-434E-BA69-911A0B7ED155.jpeg

[Twokids]

Savage - will do. Thanks.

[EuropeanAM]

Don - Will get that fuel filter replaced right after I replace my fuel lines. Parts on the way.

Bridged gaps in 1 and 5, 4 was getting there. This was after a 3 hour limp back to dock and 30 min of troubleshooting on the muffs.

75E4FB15-2219-434E-BA69-911A0B7ED155.jpeg

Definitely agree with Savage on the T-stats (they are very critical).

Surely you have more than 3 hours and 30 minutes on those plugs.

[Twokids]

Definitely agree with Savage on the T-stats (they are very critical).

Surely you have more than 3 hours and 30 minutes on those plugs.

Of course, more like 3+ years thanks to my ignorance. Had a 100k mi automotive mindset. Never considered plugs as a annual maintenance item. Lesson learned. Will replace plugs soonest however I am reluctant to wreck a new set of plugs till we get the fouling issue resolved.

What I was trying to convey was that as soon as the problem started I pulled the plugs and inspected. At that time they sere a little sooty but but not carboned up like that. That buildup occurred in the 3 hours it took me to get back to the ramp which probably explained why the engine performance progressively got worse.

[Twokids]

Better check the thermostats and make sure the motor comes up to 120*-130*F at idle.

Pulled both thermostats, unfortunately tore both gaskets

Each stat opened up about 145* and fully opened around 160*

No debris in cooling passages.

[SJSharky00]

Sounds very similar to my issue. Was a bad coil pack on #4.
Spark test like Don said.

[Twokids]

Thanks Sharky. Tested spark this morning and found all 6 coils to be good.

[EuropeanAM]

Don't forget that it is possible for the plugs to be the culprit... or at the very least, part of the problem. Have seen that literally hundreds of times.

Definitely investigate the excess fuel problem (make sure it's not contaminated fuel also... that can be a real PIA to diagnose until you happen to connect the engine to a separate tank of fresh fuel, and run the engine for long enough to turn over the fuel (at idle, will run almost 25 minutes on what's in the system).

[JAZII]

Thanks Sharky. Tested spark this morning and found all 6 coils to be good.

I would lake test it to make it act up.
I would hold it at the 4500 rpm wall for a bit then just kill the key! THEN CHECK EACH PLUG FOR WETNESS!

Sounds like a coil that is not completely failed. I been through this recently. Only found it by doing what I stated above.

Best of luck.

[Twokids]

Don/Jazii thanks for feedback. Going to button it up with new plugs, fuel lines/bulb and fuel filter and lake test tomorrow. Will get a fuel/air pressure under load as well. If it acts up will try the Jazii coil test.

[Twokids]

Replaced spark plugs and motor ran perfect (better than ever) from idle to WOT. Got in about 1 hour of runtime. I did discover the plug wire on #5 was not snapping on plug which may have been a contributing factor to original gripe. Sent injectors out for service today as preventative maintenance. Will check plugs for additional carbon build up after a few hours run time.

Final two head hurters I’d like to resolve:

1) Still getting some fuel smell when purging the port side fuel rail schrader. Besides a leaking tracker valve diaphragm is there any other failures or things I can inspect that could cause this?

2) Performed 1 pressure test under acceleration. BTW, not easy to do on back of a bass boat while relying on your kid driving the boat to manage the following sea with the cowling off. Air pressure was steady at 80psi but the fuel pressure did drop from 92 down to 87-88 until the nose dropped and boat planed off then pressure went back up to a solid 92 thru rest of power band. Did not seem to impact performance though. Is this slight pressure drop normal under heavy engine load?

[lpugh]

No it is not and it should a 14 psi spread between air and fuel
Be sure to pump the bulb till firm and recheck
Also reverse the gauge hook to verify readings are the same with both gauges
Liquid filled gauges I hope?

[Bob G.]

Don't forget that it is possible for the plugs to be the culprit... or at the very least, part of the problem. Have seen that literally hundreds of times.

Definitely investigate the excess fuel problem (make sure it's not contaminated fuel also... that can be a real PIA to diagnose until you happen to connect the engine to a separate tank of fresh fuel, and run the engine for long enough to turn over the fuel (at idle, will run almost 25 minutes on what's in the system).

Don,

If both sides of the VST were drained with the U hose, would that remove most of the fuel in the system?

[gocats]

Have you checked the coils? They are known to cause similar problems.