Outboard woes



After our launch in early November, we thought we were done with major projects for the year.  Circumstances conspired differently.  We quickly learned that our Suzuki 20hp fuel-injected, four-stroke outboard was overheating the first time we took the dinghy into the dock.  A red light came on and it cut-back to limp-mode, controlling its fuel injection and ignition timing to keep rpm down low.  At that point we took Reach to the dock for a week for a massive cleaning and would have to deal with the outboard later.




We bought this Suzuki three years ago and it’s been an impressive performer; we just love it.  The 20hp adds a nice amount of power to our far-reaching dinghy excursions and it has been trouble-free, until now.  The four-stroke eliminates the need for an oil:gas mixture and fuel-injection literally sips gasoline with its precise computer control.  We guess that we might use around 15 gallons of gas every six months of full daily use for fishing and landing.  Amazing!


Back on a mooring, Mark started to trouble-shoot.  There was plenty of oil where it should be and water flowing out the exhaust.  A check in the manual confirmed that the solid red light indicated an overheat.  With water flowing he checked the thermostat, which had water flowing to it once removed.  The thermostat was working as it should, opening at ~120˚F based on a high-tech stovetop test.  Mark ran some salt-away through the cooling system a few times for good measure.










Since plenty of water was flowing, we were suspicious that sensors or possibly the onboard computer was malfunctioning.  



Mark ordered a Suzuki diagnostic test kit from Ebay and soon had the computer hooked up to the outboard to check readings.  




The onboard computer tracks everything, from temperatures, to running time in various speed ranges, to … well here is a partial list that you might also find interesting:


Save date 2016/11/12

Engine information

  • Power 20PS  
  • ECM ID 33920-89L21
  • Engine Type 4 stroke 327cc


SERVICE DATA

Item Data Unit

  • ENGINE SPEED 938 rpm
  • IGNITION TIMING BTDC 5 °
  • MANIFOLD ABSOLUTE PRESSURE 301 mmHg
  • MANIFOLD ABSOLUTE PRESSURE 40.1 kPa
  • MANIFOLD ABSOLUTE PRESSURE 11.84 inHg
  • BAROMETRIC PRESSURE 764 mmHg
  • BAROMETRIC PRESSURE 101.9 kPa
  • BAROMETRIC PRESSURE 30.12 inHg
  • CYLINDER TEMPERATURE  62 °C
  • CYLINDER TEMPERATURE 144 °F
  • INTAKE AIR TEMPERATURE  35 °C
  • INTAKE AIR TEMPERATURE  95 °F
  • BATTERY VOLTAGE 13.04 V
  • FUEL INJ. PULSE WIDTH 2428 us
  • INJECTED FUEL AMOUNT   5 mcc
  • HIGH FUEL PUMP DUTY 56.0 %
  • IAC VALVE DUTY 16.3 %
  • THROTTLE POSITION ANGLE 0.49 °
  • THROTTLE POSITION SNSR OUTPUT 0.68 V
  • EMERGENCY STOP SWITCH OFF
  • CTP SWITCH OFF
  • NEUTRAL SWITCH ON
  • NO. OF TP SENSOR FAILURE   0 times
  • NO. OF INTAKE FAILURE   0 times
  • NO. OF MAP SENSOR FAILURE   0 times
  • NO. OF CKP SENSOR FAILURE   0 times
  • NO. OF CMP SENSOR FAILURE   0 times
  • NO. OF CYL. TEMP. SNSR FAILURE   3 times
  • NO. OF IAT SENSOR FAILURE   0 times
  • NO. OF FUEL INJECTOR FAILURE   0 times
  • NO. OF OIL PRESSURE SW FAILURE   0 times
  • NO. OF OVER-REVOLUTION   0 times
  • NO. OF LOW BATTERY VOLTAGE   0 times
  • NO. OF LOW OIL PRESSURE   0 times
  • NO. OF OVERHEAT(GRADIENT)  26 times
  • NO. OF OVERHEAT(TEMP.)   0 times
  • TOTAL OPERATION TIME (HRS.) 133 h
  • TOTAL OPERATION TIME (MIN.)   4 min
  • 0-1000 RPM 2010 min
  • 1000-2000 RPM 1196 min
  • 2000-3000 RPM 1076 min
  • 3000-4000 RPM 260 min
  • 4000-5000 RPM 2874 min
  • 5000-6000 RPM 566 min
  • ABOVE 6000 RPM   2 min
  • ELAPSE TIME FROM REMINDER CANCEL  43 h
  • NO. OF OIL CHANGE REMINDER   2 times
  • IDLING OP. TIME 484 min
  • NO. OF SHIFT F 5802 times
  • NO. OF START-WOT TIME(0-1 MIN)   6 times
  • NO. OF START-WOT TIME(1-5 MIN)   2 times
  • NO. OF START-WOT TIME(5-10 MIN)   0 times
  • NO. OF ST-WOT TIME(ABOVE 10 MIN)   0 times
  • NO. OF STARTING(FOLLOWING -10°C)   0 times
  • NO. OF STARTING( -10-0 °C)   0 times
  • NO. OF STARTING( 0-10 °C)   0 times
  • NO. OF STARTING( 10-20 °C)   0 times
  • NO. OF STARTING( 20-30 °C)   0 times
  • NO. OF STARTING( 30-60 °C)   0 times
  • NO. OF STARTING(ABOVE 60 °C)   0 times
  • THE LOWEST BAROMETRIC PRESSURE 542 mmHg
  • THE LOWEST BAROMETRIC PRESSURE 72.2 kPa
  • THE LOWEST BAROMETRIC PRESSURE 21.32 inHg
  • THE HIGHEST BAROMETRIC PRESSURE 779 mmHg
  • THE HIGHEST BAROMETRIC PRESSURE 103.9 kPa
  • THE HIGHEST BAROMETRIC PRESSURE 30.67 inHg
  • THE LOWEST INTAKE AIR TEMP.  18 °C
  • THE LOWEST INTAKE AIR TEMP.  64 °F
  • THE HIGHEST INTAKE AIR TEMP.  64 °C
  • THE HIGHEST INTAKE AIR TEMP. 147 °F




The temperature sensor read what it was supposed to on the computer (CYLINDER TEMP) and it did show an overheat when at high rpm, although the actual resistance values directly on the sensor were about 10x off from what the manual stated.  Even though it is not expected to be a replacement part, we decided to order a new sensor that would take a week to ship to eliminate that possibility from the equation.




While waiting for the sensor, Mark changed the impeller from the lower-unit.  It was in decent shape and can be saved for a spare.  The water test still showed water flowing, yet a thermal gun did indicate higher temperatures being reached in the head.  






Finally, with a new sensor received and installed we still had a problem and had to take it into the shop, since it needed access to a bench and Suzuki parts.







The folks at the shop were knowledgeable and confirmed what we already knew to date with their computer.  They agreed with Mark that the two possibilities remaining were an onboard computer malfunction or a internal clog with possible internal corrosion.  The next step was major surgery.





Taking off the motor and removing the head from the block revealed what we needed to see of the internals.  The bad news is that there was a slushy clog all around the cylinders, allowing water flow but not in all the areas that needed cooling.  This slush appeared to be mostly sand and salt build-up!  It either accumulated over time in the cooling system, or one unlucky event started a clog that quickly backed up.  












The good news is that all of the aluminum metal appears in good shape and not corroded, as we had feared.  The exhaust manifold is often the first to go and that looked like new.  The head and cylinder manifold were also in very good shape. The folks working on our engine were pleasantly surprised too, since they’ve seen much worse in their experience.










Compression was a bit low, although still in spec, and one of the sets of valves were not holding fluid because of some carbon buildup, but they will be cleaned and reseated with their springs as a routine matter while the head is open.  This will restore higher compression.  We’ll also get a new thermostat, an oil and filter change and new gaskets for both the head and casing for the final reassembly.  All of this is taking place with an interlude for the holiday weekend impacting parts’ shipping and labor, so it looks like we are rowing for another week!




We are, however, grateful that we found this clog now rather than in the out islands where we could get into big trouble, and that we’ll have virtually a new outboard once it’s reassembled.  The lesson learned is that we really need to do a weekly freshwater flush to avoid the accumulation of salt and sand in the cooling system.  The manual recommends it, yet we had never done this since we use the dinghy daily.  We’ll also use a fuel additive like Yamalube for good measure to help the valves and rings from getting carbon buildup.



© M&M 2016