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Honda will not exceed 4000 RPM

jaccoo

New member
2006 Honda BF150 (575 hrs)

Motor has been running flawlessly since April, then in July cloudy fuel caused my engine to run poorly. I used the boat A LOT for commercial fishing so it never sat at the dock for more than a day without use


  • · Drained on motor vapor separator
  • · Replaced on motor Low and High pressure filters, and drained the onboard water separator
  • · Replaced the Racor Filter
  • · Replaced spark plugs (using NGK IZFR6F11) – all four old plugs were lightly brown

Now trying to get the motor running on an external tank.


  • · Under Load, With throttle fully opened, the RPM will not exceed 4000 RPM – but if I back off the throttle, the boat will surge to 4200 RPM and then fall back to 4000 RPM within a second. I can play with the throttle and duplicate this RPM behavior.
  • · When in Neutral, motor runs perfectly. RPM can increase with throttle – can easily get to 5000+RPM. RPM behaves as expected

What could be the problem??

  • · No warning lights or sounds
  • · O2 sensor – where is it, I can’t tell from the service manual
  • · High Pressure fuel pump filter screen?
  • · Solenoid Screen
  • · Vacuum hoses
  • · Fuel pressure (regulator)
  • · Restriction in the fuel rain screen
  • · Ignition Coil
  • · Spark in each cylinder

Thank you for your time.
 
UPDATE -
ran the engine in neutral at 3000 RPM
while running, disconnected the "Ignition coil 3P connector" from the "Ignition coil" for individually for each cylinder, one at a time.
all four cylinders resulted in the engine sputtering, then returning to normal engine operation when the connector was reconnected.

is my understanding correct, that the coils are not the problem and that all 4 cylinders are firing correctly?
 
That's called a "Dropped Cylinder Test", and yes, that tells you all cylinders are firing, so coils and plugs are likely good.

I don't have any direct experience with the 150, but clean items 9 and 10 in the following link:
http://www.boats.net/parts/search/H...006/BF150A6 LA/FUEL PUMP FUEL HOSE/parts.html

This link shows where the HO2 sensor is located. Part number 7.
http://www.boats.net/parts/search/Honda/Outboard Engine/2006/BF150A6 LA/EXHAUST PIPE/parts.html

Also, there is a fuel pressure regulator that sits on top of the fuel rail. I have no idea how to test that, but it is part # 5 in the following link:
http://www.boats.net/parts/search/H...F150A6 LA/INTAKE MANIFOLD INJECTOR/parts.html
 
Thank you for the information! I need to pull the old girl to get to items 9 and 10.

UPDATE - I have yet to perform the recommendations from CHAWK.
I as the engine was purring along at ~3900 RPM, I tilted the engine up to get over a sand bar, and as the engine tilted, the RPM shot to over 5000 as the prop came close to the surface of the water. the prop never came out of the water. Also, I never touched the throttle
As I successfully passed over the sandbar, I tilted my engine down and the RPM returned to ~3900. again, I never touched the throttle

I thought this was interesting, and maybe someone reading this post will be able to interpret this and be able to figure out what my issue is... (praying)
 
Have you checked the doublebottom for water? Just sounds like your pushing alot more weight. Try disconnecting the battery overnight possibly the computer needs to reset new values. Hopefully hondadude will chime in and point you in the right direction. Probably something real simple?
 
Hello KIMCRWBR1, could you please explain what the 'Doublebottom' is? then i can check it... thanks

regarding the batteries, i always turn off the battery selector switch whenever i dock the boat... i will try disconnecting the batteries just in case... (i will try anything at this point)

i will try to get her pulled this weekend to dive into Chawk's recommendations
 
UPDATE:
I just got the boat back from the mechanic and the following items were replaced
- All 4 fuel injectors were clogged, and I asked for new ones to be put in, instead of cleaning them
- The high pressure fuel pump was weak, and replaced
- The VST was cleaned
- Replaced items 9 and 10 in the following link: http://www.boats.net/parts/search/Ho...OSE/parts.html



She runs like a champ on an external 5-gallon tank.

I need to have the internal tank cleaned. a new tank was installed four years ago, but i am getting water in it some how... i use PRI-G fuel treatment to stop phase separation, but maybe it is not working.

Thank you all for your help
 
Good to hear that!

About the only way water can get into the fuel tank, except for bad fuel in the first place, is (1) the seal on the fill cap has failed, or (2) the cover on the vent tube outlet on the outside of the gunwale is missing or not properly covering the vent tube. New fill caps with good seals can be purchased from about any marine products firm.
 
Jaccoo,
Thanks for the thread! I have 2006 225 with the same issue. The starboard engine runs fine, the port is off about 500 rpm with top end only reaching ~5000. I'm guessing fuel injectors or fuel rail, but will check what you have done first. They probably just need a good mechanical overhaul after 11 years of operations. Plan to do it this winter.

If you don't mind me asking, what was the repair bill?

UPDATE:
I just got the boat back from the mechanic and the following items were replaced
- All 4 fuel injectors were clogged, and I asked for new ones to be put in, instead of cleaning them
- The high pressure fuel pump was weak, and replaced
- The VST was cleaned
- Replaced items 9 and 10 in the following link: http://www.boats.net/parts/search/Ho...OSE/parts.html



She runs like a champ on an external 5-gallon tank.

I need to have the internal tank cleaned. a new tank was installed four years ago, but i am getting water in it some how... i use PRI-G fuel treatment to stop phase separation, but maybe it is not working.

Thank you all for your help
 
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