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  1. #1

    Default Honda will not exceed 4000 RPM

    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.

  2. #2

    Default Re: Honda will not exceed 4000 RPM

    i found this post... i will ask my mechanic to check this out... when they can get it in... there is a 2 week wait...

    http://www.marineengine.com/boat-for...ormance-issues

  3. #3

    Default Re: Honda will not exceed 4000 RPM

    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?

  4. #4
    Join Date
    Sep 2008
    Location
    Hague, Virginia, USA
    Posts
    3,725

    Default Re: Honda will not exceed 4000 RPM

    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/Ho...OSE/parts.html

    This link shows where the HO2 sensor is located. Part number 7.
    http://www.boats.net/parts/search/Ho...IPE/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/Ho...TOR/parts.html
    CHawk 25 DLX

  5. #5

    Default Re: Honda will not exceed 4000 RPM

    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)

  6. #6
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    3,539

    Default Re: Honda will not exceed 4000 RPM

    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?
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  7. #7

    Default Re: Honda will not exceed 4000 RPM

    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

  8. #8

    Default Re: Honda will not exceed 4000 RPM

    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

  9. #9
    Join Date
    Sep 2008
    Location
    Hague, Virginia, USA
    Posts
    3,725

    Default Re: Honda will not exceed 4000 RPM

    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.
    CHawk 25 DLX

  10. Default Re: Honda will not exceed 4000 RPM

    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?

    Quote Originally Posted by jaccoo View Post
    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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