2010 175 HP Optimax missing

[jeffadams]

I have a 2010 175 standard optimax SN#1B789623 that was missing the last time I took it out. I changed plugs (IZFR5G @ .031 gap) and fuel filter. Today I ran it, and it only missed when I first took off and this only lasted for a minute. After that, I ran it for 30 minutes with much of the time at WOT. During that period of time, the engine missed for just a second while getting on plane. After that, I couldn't get it to miss.

I'm planning a trip, so I'm hoping that I've fixed the problem, but I'm still concerned because it missed today, even after changing the plugs yesterday. I was wondering if the engine might have a coil going out and it only shows itself when cold. Does anybody have any suggestions about checking something else? I do use 87 non ethanol, DFI oil, quickleen every tank and follow Don's annual maintenance plan. Thanks.

[EuropeanAM]

Possibly carbon floating around in there- running Quickleen?

[jeffadams]

I do run quickleen in every tankful. I'm going to add a couple teaspoons of quickleen to the fuel filter and run that through the engine. A Merc tech said that he sprays a little mercury decarb in the inlet to the compressor when the engine is idling on the muffs and shuts it down and lets it soak. I'm not too keen on spraying anything in the compressor inlet.

[potomacbassin]

Not saying this is the problem but I had similar symptoms and it ended up being my TPS. I troubleshot everything like spark, coils, replaced sparkplugs, etc. before trying the TPS. It was intermittently going out on me at WOT and when getting on plane. Just something you should keep in the back of your mind.

[EuropeanAM]

DO NOT spray "decarb" (or power tune) into the compressor. It can cause the engine to rev uncontrollably, potentially resulting in severe damage.

Also don't use Power Tune unless you are prepared to replace the spark plug after the first run.

[jeffadams]

Thanks for the suggestion. I will keep this in mind.

[jtracc]

I have a 2013 150 pro xs and this past summer it was running like crap. I noticed the spark plugs were gapped at .031 and I gapped them to .042 and used premium gas. Soon as I did this she ran like a top man.

[EuropeanAM]

I have a 2013 150 pro xs and this past summer it was running like crap. I noticed the spark plugs were gapped at .031 and I gapped them to .042 and used premium gas. Soon as I did this she ran like a top man.

Good info- In your area of the world both the plug gap and fuel "may" have helped.

Here in the lower 48... I'd be looking at the plug gap (and stick with the recommended fuel).

[jeffadams]

I'm still having problems with my engine missing while planing and usually when accelerating, but all of this occurs intermittently. I've checked coils, injectors, plugs, and fuel. I did find the posts on two coils were somewhat pitted due to possible arching, but not sure that would cause it. Today, I idled the engine on muffs and it ran rough. When I shut the engine down and restarted, it ran smoothly. Could these things be a symptom of a bad Throttle Position Sensor, as Potomacbassin mentions above? I'm out of ideas.

[lpugh]

Jeff try this for starters, Get a spray bottle filled (very fine mist)with water and with motor running spray down the plug, wires and coils to see if it induces a misfire. I do not mean hose it down, mist it. If so replace component's that leak and be sure to use a liberal amount of dielectric grease. If you are not afraid of getting bit do as I do and just run your hands over all components, you will not get shocked if component's are good. Look very close at the coil towers for carbon tracks. I think you may find secondary leaks to ground or low coil output. Also use a kv tester to check available voltage from the coils such as this one...… spark gap tester
They should bridge about the same gap probably in the 30 to 40 kv range, I do not know what the coil output for your motor is, but I would bet it is at least 28kv or more.
Very crude rule .030 plug gaps 30kv, .040 gaps 40 kv etc. cylinder pressures and air fuel ratios also enter into this equation. Higher pressures and leaner AFR increase demand

[EuropeanAM]

Might want to test the plug wires with an ohm meter (flex wire around and check for drastic changes in reading).

Also visually inspect under bright lights for any signs of abrasion, wear, chafing, cuts, or chalky/burnt spots.

While KV testing can be very useful in some applications, keep in mind that some (not this particular one) of the coils and ignition systems used in the Optimax engine line are MULTI-STRIKE ignition components, and may react or result differently than expected.

[jeffadams]

Ipugh, I did as you said and sprayed water and checked for jumping spark, but found no issues. Fuel and air pressures are in spec. I do notice that when I'm getting up on plane and the engine starts missing, the warning horn sounds. It only seems to beep at each misfire and then it stops once I get on plane.....all of this happens in a few seconds during acceleration. The engine runs well once on plane and running with only a momentary misfire now and then....usually when moving the throttle up or down. I checked all coils and they are in spec, as far as the ohm specifications for the ABCDE contacts on each coil. Additionally there is a good spark on each with the spark tester. I don't have a gap tester as you described above.

[lpugh]

With that info I would test primary voltage at the coils or b+ side of the injectors while alarming. I would also use a DSO to monitor TPS signal. Keep in mind I have fair understanding of these circuits but I am not a Mercury Tech. Dons word should always supersede mine. He has far more experience than I in the marine field.
With the alarm you should have data stored that would help pin this down. It would be very worthwhile in your case to have dealer scan the system for you I think

[EuropeanAM]

With the alarm you should have data stored that would help pin this down. It would be very worthwhile in your case to have dealer scan the system for you I think

+100

Get the PRINTOUTS of the Run History, Freeze Frame (Fault) History, and Fault Seconds Counters. I would be happy to review them here as images, or by email as PDF files.

This will be your least expensive route to a successful diagnosis and repair.

[jeffadams]

+100

Get the PRINTOUTS of the Run History, Freeze Frame (Fault) History, and Fault Seconds Counters. I would be happy to review them here as images, or by email as PDF files.

This will be your least expensive route to a successful diagnosis and repair.

I have always hoped that people with engine issues follow up and report back on what problem was found. This is what was found thus far on my problem. I sent my 175 optimax to the local Mercury dealer and he hooked it up to the CDS. He says that it showed a defective shift switch. As I understand from his explanation, the computer did not recognize when the engine was shifted from neutral to forward because of the faulty shift switch. When trying to get up on plane, apparently the PCS sees that action as overreving the engine while in neutral or something like that, and puts the engine in guardian mode and somehow recognizes a bad switch. Perhaps Don can explain better than I can. This causes the engine to sputter and feel like a misfire. The problem has been intermittent, and occasionally I could get on plane, but the last time I ran the engine, it would not go on plane. Anyway, I pick up the boat tomorrow and I'll run the engine then and report back.

[lpugh]

Thanks for the follow up it helps us all learn more. I would be very optimistic that diagnoses may solve your issue

[EuropeanAM]

I AGREE. Simple switch- indicates "In Gear" or "In Neutral". Closed when in neutral, Open when in gear.

Note: Revving the engine in neutral can also set this fault... if you have NOT been doing that, it's highly likely that replacement of the switch will resolve the problem.

Great example of how the info from the PCM Freeze Frame (Fault) History can actually save you a lot of money. Who knows how many parts you would have "thrown" into the mix before you stumbled onto the shift switch (unfortunately, those "thrown" parts can add more problems, further complicating things).

Good job!

[jeffadams]

Ran the boat today and it did great. The shift switch was the problem. Yes sir, changing parts without knowing what's going on is expensive. I almost bought a TPS.....glad I brought it in!

[potomacbassin]

[lpugh]

I AGREE. Simple switch- indicates "In Gear" or "In Neutral". Closed when in neutral, Open when in gear.

Note: Revving the engine in neutral can also set this fault... if you have NOT been doing that, it's highly likely that replacement of the switch will resolve the problem.

Great example of how the info from the PCM Freeze Frame (Fault) History can actually save you a lot of money. Who knows how many parts you would have "thrown" into the mix before you stumbled onto the shift switch (unfortunately, those "thrown" parts can add more problems, further complicating things).

Good job!

Seen that sooo many times, simple problems sometimes become major expenses to overcome, Could have just tightened the loose battery ground on the block instead of replacing the Battery, Alternator and starter