Suzuki df300ap going into half power limp mode

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Dear Suzuki Marine Mechanics and shop owners - Listen to your customer rather than ignoring them, and for the love of GOD, use some real troubleshooting logic beyond ECU data!   

I’ve seen too many mechanics rely on their title in which they received through some form of training, especially around the Suzuki brand.  There is much more to fixing a Suzuki outboard motor than just letting the ECU tell you what the problems are and replacing a part.  It’s this narrow-minded thinking that has boat owners dealing with problematic motors until they give up because the trained marine mechanic couldn’t fix it.  We all have that friend whose motor never quite ran right from the get go despite the thousands of dollars he paid to have it fixed.  Defective motor?  Perhaps, but not likely.  Subpar mechanic?  More than likely!   


It’s okay for us Suzuki outboard owners and other brands to be right now and then!  Hell, some of us may even know how to fix the Suzuki over rev and code throwing issues in which we bring to you but choose to let you get dirty instead.  Some of us may be engineers, communication and electronics experts, medical diagnostic specialists, physicians, designers, etc., and have a high level of logical problem solving that enables us to understand a simple computer controlled air pump.  Someone with a high level of logic in one field of study can strategically figure out problems in other fields of study despite being trained, so consider that next time when you speak down to your customer from your mighty title as lead mechanic.


Technical training gives the mechanic some basic knowledge to start and build on, but only truly good mechanics possess and assert some type of logical forward thinking rather than living solely on recall.  Sadly, that’s about as far as I see many so-called experts go, and what I experienced at Precision Marine in Largo Florida under the new ownership.   The previous owner, Robert Mostowski may not have been good with customers, and took twice as long and cost twice as much, but it appeared from the few times I used him that he at least knew the motors. 


You’ll read the story below, but I pushed back against Precision Marine until I was blue in the face, telling them they were being narrow-minded in their diagnostics of my Suzuki df300ap, and was forcing me to chase an issue they should be able to solve while on my six year warranty rather than on my dime, and if I proved they were wrong I’d offer up a detailed article to the public... and here it is.  A bit of logical troubleshooting from their mechanic and new owner could have earned them my business, but instead earned this negative review.  Suzuki corporate wasn't any better, as they just took the word of Precision, but more on that later. 


Being that many aspects of my life, from my Aviation Electronics in the US Navy and computer programming background to my current field in RF communications, they all require a form of logic beyond simple recall logic to find the root of problems that may have never been encountered, or those that aren’t logical based on the data presented.  The first and most important step in troubleshooting as logic dictates is to accurately identify the problem through information relevant to the problem, and understand how to use that information.  Below is my account of how and what information was presented to Precision Marine and a progression of what unfolded.     


Problem Presented:  2016 Suzuki df300ap outboard going into limp mode often around 3000 rpm for no apparent reason.

Engine Data Presented.  I presented a printed ECU report showing 78 engine hours that had 18 loggings of recent over revolutions, 20 CMP sensor failures, and 1 CKP sensor failure at around 66 hours.   

Owner Feedback Presented.  I stated I have never observed the motor hit the rev limiter and that it is not going into over revolution, thus causing limp mode / half power to activate, and certainly not 18 times.  I further stated the following:

  1. I don’t see any logical reason why surpassing the rev limiter would put the motor into limp mode rather than simply interrupting spark/timing/fuel as most if not all motors do, and certainly not for 30 minutes one time, and 10 the next, and so forth, or for any amount of time as that would be dangerous in a lifesaving condition.
  2. Motor has gone in and out of limp mode while at a steady rpm of 3000, and returns to normal operation at various times from 20 second to 30 minutes.
  3. Motor has gone into limp mode upon starting and throttling up to 3000 rpms before coming anywhere close to the rev limiter.
  4. Motor goes into limp mode usually around 3-4000 rpms.
  5. I ran the motor at 6300 rpm for several minutes multiple times with no over rev activation.
  6. Motor has been having this problem and getting worse from 66 hours onward.
  7. I suspected and asked if it could be a possible ECU malfunction, or bad electrical connection causing false readings.

So the mechanic and shop owner were presented with this information to troubleshoot the motor.   Obviously, the first step is for them to take their own ECU reading and see what current data is showing.  Below are side by side extractions of my data and that from Precision.

As you can see, the number of over revs went from 18 to 25 over 6 additional run hours on the motor.  I’m not discussing the CMP failures in this article because they have seemed to clear up.  I will note however, that before Precision pulled their own data, and after looking at my report from the motor they said the CMP failures were from the over revs. 


Though I’m sure this motor has not had an over rev, I am not sure if is it could cause a CMP failure which threw the following codes on both reports. I do question that the over revs have continued from 67 to 84 hours, yet the failures have stopped.   Now that Precision Marine had their own copy of the ECU data it was time for them to take the next step in logical problem solving, which is to determine from experience what information is important to solve the problem, what information can be ignored, and if any further information is needed to solve the problem.  These are the minimal of basic logical questions that should have been weighed in by the mechanic and shop owner if they were worth their weight as problem solvers rather than data readers. 

Is there a possibility of faulty engine data being sent to the ECU? Are the customer details accurate of an over rev or another issue? Have we experienced this issue before? Is there anything that could skew the readings?


I asked a few other Suzuki mechanics the following questions.  Is there a possibility of faulty engine data being read by the ECU? They answered yes. Do my details sound accurate of an over rev or another issue? They responded by saying it was definitely not over rev. Could a bad battery switch, lose or corroded contact in the starting circuit cause the problem that I presented? Absolutely, if your voltage supply is fluctuating then this can make the Suzuki do all kinds of weird things, including kicking the motor into limp mode. These motors need a clean, stable, and ample voltage supply to run without problem. Have you experienced this issue before? Yes, we had a few customers with this issue where the data didn’t match the symptoms and found each of them to be power related and not what the code was throwing.


Right there it came to me.  My battery switch may be going bad.  It’s the one thing I didn’t change even though I thought of and checked it for continuity multiple times.  It was clean and at each activation by the key switch it closed the circuit as intended.  At over $200 and working it wasn’t a cheap swap out thought.  I went home and noticed the switch also had a manual position that I never had to use, so I flipped it over to that.  I took the boat out and ran a test run for nearly an hour with no issues.  I flipped the switch back to auto, restarted the boat and the problem returned within 15 minutes of running.  Since then I have had the boat on 3 offshore trips, about 9 hours, and have had no more problems.   When I switch back to auto mode on the switch it quickly kicks the motor into limp mode within minutes.  After inspecting the switch closely, any decent shock or vibration causes the switch to disengage, just slightly out of contact.  The design has a tight tolerance on contact at the on position, and a long 1 inch travel to the off position, so slight movement will open the circuit.


I am nearly sure the failure reason is from those who have worked on my boat in the past, as the house side has never failed and it’s activated each time the start side is.  In fact, when Robert’s guys, the old owner of Precision marine installed my motor it came back with a broken switch that I had to replace.   I wasn’t able to prove they did it, but I know.  Most don’t realize it’s a remote keyed switch operated from the helm, and if used manually, you have to press down to turn, otherwise a direct turn strips the gears and results in damage.


Regardless, problem solved by speaking with a few mechanics that spent the time to troubleshoot their clients’ issues rather than just read a data printout as precision marine did.  Once again it’s apparent that they did not use any logic, but rather took the data from the motor and failed to consider my details, as they called the next day stating that is was in fact caused by me over revving the motor, and if I wasn’t noticing it then it is likely prop slippage due to a small cut on the blade... and they could sell me a prop as the first step to fixing the problem!  My God, I felt like I was on a prank reality show at this point. I have been running the same prop on my last motor and this motor with no issues.  The prop has a small blade-edge cut that I filed down.  It is at most, 3/32nd deep by ¾ long and shows no sign of being an issue!  Anyone with ears and a sense of feel can tell when your prop is slipping, cavitating, ventilating, vibrating, or just straight out catching air.  There’s no vibration, no sound pitch harmonizing, no surging, no high revving, no slurping of surface air, etc.   They ended by offering to sea trial the boat and fit the right prop at a hundred plus dollars per hour, or instructed for me to come and get the boat. 


Wow, last I experienced on my Mercury 250, over rev was nothing more than the motor hitting the limiter and creating that unmistakable high rev [pap pap pap pap pap pap] sound, but according to Precision Marine it cuts the motor in half power for upto 15 minutes on my Suzuki, and could last for 30 minutes!  I saw no indication of logical troubleshooting so I placed a call to Suzuki hoping to get them involved.  Surely Suzuki would have answers and listen to the customer.  Not so fast, Suzuki has no tech support for the owner, so it’s up to the dealer to speak to them.  I called Precision back and told them Suzuki would call them soon to discuss, and asked me not to pick up the boat until they had a chance to get involved.  I made it very clear that I wanted Precision to pass on my questions as listed above to Suzuki for my own clarification, which they failed to do.  


I needed to at least clarify some things before I left their shop so I asked them if there was anything else that could cause this motor to act this way, and they said NO.   “Could the ECU be sending bad information?” They said NO.  “Any chance a bad sensor could make the motor think it is being over revved when it’s really not?” Again, NO!  “Bad power connection or fluctuating supply?”  The mechanic ended by saying, “It is without a doubt, 100% an over rev issue and that is final!”  I tried to reason with them to get this solved and they asked me to not come back.   The owner stated that I filed a complaint with Suzuki and began spouting out things that I supposedly said to Suzuki.  Wow, it felt like I was in high school again!  I highly doubt Suzuki would get into a blame game, but whatever.


Confidence can’t hide ignorance when those that you take aim at have an ample supply of intelligence, common sense, and a mouth like I do.   I gave them my final departing statement and told them they were wrong and weren’t listening to me, and when I figured out the issue that I would shout it from the mountain tops (sand dunes in our case) with no hesitation on calling them out if they were wrong.   So here I am, calling out Precision Marine and their ineptitude when it comes to Suzuki motors, and their poor customer management skills as they were unwilling to listen to the customer. 


Conclusion:   It seems the personality of this shop continued where it left off from the previous owner Robert Mostowski, and the skills are very poor in my opinion even retaining the old staff.  It appears that Robert Mostowski has returned to work there from word on the street, perhaps asked back by the new owner due to a lack of know-how, but that’s just a good guess.  Had Precision Marine listened to my details and took them into serious consideration, I would say they could have earned a lasting customer, but I’m not the right type of client for them as I have a mouth, brain, and not afraid to use either before opening my wallet.  That caused issues as well with Robert in the past.  I felt like the new owners were more interested in getting money from me by troubleshooting things they should have known, as  I don’t know how a certified mechanic could conclude the things above when they are so inaccurate.  Had they explained my details to Suzuki, I can only believe that Suzuki would have been able to solve it, or at least I hope they could have. Perhaps they don't like Suzuki warranty work.  As it stands, they were BOTH WRONG! 


I seems that Suzuki will authorize nearly anyone as a dealer,  according to a few people in the business that will remain nameless.  Good luck Suzuki owners...They are great motors but pick your mechanic wisely.