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  1. #1

    Default BF40 Stalls when warm

    2012 BF 40, fuel injected. Bought new. No problems for years. Last summer, ran it out to the lake and ran fine all the way. Fished several hours, started to return and engine stalled about 4000 rpms, consistently. Looked at fuel tank (portable) and saw that it was trying to collapse ( it was near 100 degrees outside). Checked vent and it was open. Got home and ordered and new fuel line and put on. Same problem on subsequent trip. Ran fine when not hot outside that morning, but on the way back it would stall. Replaced spark plugs, no improvement. Fished this winter with no problems or stalling. Went fishing again today with temps near 90, on the way out from the boat ramp, no problems noted. However, when I returned it began to stall again. I have also opened and checked the water separator and it was clean. Is there anything I need to check that I am overlooking. I am thinking that the problem is in the fuel tank but I am unsure.

    Thanks for any help.

  2. #2
    Join Date
    Mar 2009
    Location
    Cincinnati, OH USA
    Posts
    4,398

    Default Re: BF40 Stalls when warm

    Try loosening the cap of the fuel tank to create a different vent.

    It sounds like you have a portable tank and not a build in tank. If the vent is not working right, it will cause the tank to implode.

    I can not explain why it only has a problem in the heat....perhaps something inside the vent expands (maybe some debris) and clogs the passage.

    In any case, loosing the cap will allow air to flow in and probably solve your problem.

    If it does, then it is time for a new cap/vent.

    Mike

  3. #3

    Default Re: BF40 Stalls when warm

    Thanks I'l try that

  4. #4

    Default Re: BF40 Stalls when warm

    Replaced fuel cap and gas tank filter. Fished this morning and ran fine on the way out. On the way back it stalled again. Don't think it is the tank anymore. Any advice? this is getting frustrating.

  5. #5
    Join Date
    Apr 2016
    Location
    barnegat NJ
    Posts
    3,143

    Default Re: BF40 Stalls when warm

    Try pumping primer bulb when issue arises, If condition goes away,you have a fuel restriction somewhere

  6. #6

    Default Re: BF40 Stalls when warm

    Quote Originally Posted by johnnygjr View Post
    Try pumping primer bulb when issue arises, If condition goes away,you have a fuel restriction somewhere
    Yea I have tried that too. It seems to make no difference.

  7. #7

    Default Re: BF40 Stalls when warm

    Do these engines have a thermostat. The can't find anything about it.

  8. #8

    Default Re: BF40 Stalls when warm

    Yes, part #8 in the link below. There is also a sensor.

    https://www.boats.net/catalog/honda/...cylinder-block

  9. #9

    Default Re: BF40 Stalls when warm

    Quote Originally Posted by eneusiis View Post
    Yes, part #8 in the link below. There is also a sensor.

    https://www.boats.net/catalog/honda/...cylinder-block

    Wow thanks for that. Im going to try that next. If I replace it or find that it is okay I may just have to find a shop to take it to.

  10. #10
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
    Posts
    3,097

    Default Re: BF40 Stalls when warm

    When was the last service/cleaning done to your VST?

    Your description of symptoms involving warm engine combined with hot weather sounds a lot like the old vapor lock problems we used to have with carbureted autos.

    Just a hunch but the V in vst stands for vapor.

    Just another idea to chew on.

    Good luck.

  11. #11

    Default Re: BF40 Stalls when warm

    Quote Originally Posted by jgmo View Post
    When was the last service/cleaning done to your VST?

    Your description of symptoms involving warm engine combined with hot weather sounds a lot like the old vapor lock problems we used to have with carbureted autos.

    Just a hunch but the V in vst stands for vapor.

    Just another idea to chew on.

    Good luck.

    Good point. I drain the vapor separator all the time but I didn't know of any other maintenance needed for it. I am waiting on parts to do the thermostat change. I'm going to go ahead and do the impeller as well even though it has a strong stream.

  12. #12
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
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    3,097

    Default Re: BF40 Stalls when warm

    Hopefully others with extensive experience with maintaining the VST and associated filters will chime in with some pointers for you. I've never had one apart but many on this site are what I would call experts on the subject.

    It's not rocket surgery or brain science but there are probably a couple of finer points and do's and don'ts. I know it can be difficult to remove the screws the first time for example.

  13. #13

    Default Re: BF40 Stalls when warm

    Put in a new water pump this morning as well as a new thermostat. Took out to the lake and is still stalling. Any other advice? What can I do with the fuel delivery system?

  14. #14
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
    Posts
    3,097

    Default Re: BF40 Stalls when warm

    You may want to take out the fuel strainer...item 35 in link below....and
    clean it out. If theres gunk built up in there it could interfere with fuel delivery. Also, look at items 23 & 24 and the adjacent fitting and hose.
    Make sure those are clear and will allow the system to vent. If they get plugged with something I believe that could cause your symptom.

    Hopefully the fuel injected guys will chime in with more/better suggestions.

    https://www.boats.net/catalog/honda/...apor-separator

    Good luck.

  15. #15

    Default Re: BF40 Stalls when warm

    Quote Originally Posted by jgmo View Post
    You may want to take out the fuel strainer...item 35 in link below....and
    clean it out. If theres gunk built up in there it could interfere with fuel delivery. Also, look at items 23 & 24 and the adjacent fitting and hose.
    Make sure those are clear and will allow the system to vent. If they get plugged with something I believe that could cause your symptom.

    Hopefully the fuel injected guys will chime in with more/better suggestions.

    https://www.boats.net/catalog/honda/...apor-separator

    Good luck.

    Opened it it up no gunk. Medium looked a little dark but got lighter as it dried. The o ring to it was a Bugar to reinstall though.

  16. #16

    Default Re: BF40 Stalls when warm

    Called the shop I bought the boat from. Guy said that the BF40 have a common known issue in the vapor separator where an insulator that goes from the low to high pressure fuel pump will expand and cause these issues. He stated that he has one is the shop right now for the same issue. Has anyone else heard of this issue? He said that he was surprised Honda has not recalled the motors due to the issue, which is caused by ethanol in gas. I think that part number is 16721-ZY9-003.

  17. #17
    Join Date
    Mar 2009
    Location
    Cincinnati, OH USA
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    4,398

    Default Re: BF40 Stalls when warm

    He is correct. Your symptoms were not the typical symptoms for that problem. I guess I was sidetracked by the imploding of the fuel tank. That usually points to the tank. But I guess you got past that issue....

    Generally, when I have seen that part being a problem, the motor can not be restarted until the motor cools down. However, it may not be that way all the time. Besides the fuel, I think the heat of the engine may also add to the expansion.

    That part is actually on the output of the high pressure pump. It is just a rubber grommet. There is no Service Bulletin on it. Merely changing the part will not necessarily permanently cure the problem. You will have to remove the VST and separate the cover and the lower body. Keep the high pressure pump with the lower body and just pull it out of the grommet (which will probably stick in the cover) Remove the grommet and carefully slice about 1/16" to 1/8" of the rubber off of the narrow end (the end that is pushed up inside the cover).

    While you are at it, you can at least inspect the inside of the VST, to be sure nothing else is going on.

    Just put everything back together....and you should be good to go.....if that is the cause of the problem.

    Generally, before going through all that work and if I can get the motor to fail....I look for four things.
    1. VST has plenty of fuel....by checking the fuel from the VST drain..
    2. The high pressure pump is running....you can generally hear it .
    3. The high pressure filter has recently been changed.
    3. There is little or no high pressure fuel pressure.



    Hope this helps.

    Mike

  18. #18

    Default Re: BF40 Stalls when warm

    Quote Originally Posted by hondadude View Post
    He is correct. Your symptoms were not the typical symptoms for that problem. I guess I was sidetracked by the imploding of the fuel tank. That usually points to the tank. But I guess you got past that issue....

    Generally, when I have seen that part being a problem, the motor can not be restarted until the motor cools down. However, it may not be that way all the time. Besides the fuel, I think the heat of the engine may also add to the expansion.

    That part is actually on the output of the high pressure pump. It is just a rubber grommet. There is no Service Bulletin on it. Merely changing the part will not necessarily permanently cure the problem. You will have to remove the VST and separate the cover and the lower body. Keep the high pressure pump with the lower body and just pull it out of the grommet (which will probably stick in the cover) Remove the grommet and carefully slice about 1/16" to 1/8" of the rubber off of the narrow end (the end that is pushed up inside the cover).

    While you are at it, you can at least inspect the inside of the VST, to be sure nothing else is going on.

    Just put everything back together....and you should be good to go.....if that is the cause of the problem.

    Generally, before going through all that work and if I can get the motor to fail....I look for four things.
    1. VST has plenty of fuel....by checking the fuel from the VST drain..
    2. The high pressure pump is running....you can generally hear it .
    3. The high pressure filter has recently been changed.
    3. There is little or no high pressure fuel pressure.



    Hope this helps.

    Mike
    Wow, ok that is exactly what he said about cutting a piece of that grommet. I am going to look at it tomorrow and see if it is something I can do myself. Thanks for the help and advice I appreciate it.

  19. #19

    Default Re: BF40 Stalls when warm

    So I ended up taking the boat to the dealer for this job. They fixed it no charge. I have to give a thanks to Honda for warranty-ing this even though my outboard was11 months outside warranty!

  20. #20

    Default Re: BF40 Stalls when warm

    Hi, I have the same problem with my 2013 bf40 outboard. When I run for a long time on a bucket and the water gets hot the engine die and I have to wait for a while to run it again. But when I run it on a continues water with a hose for 44 minutes, it runs fine. Kindly ask a favor of what the dealer fix or change? Thanks a lot and God bless you.

  21. #21
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
    Posts
    3,097

    Default Re: BF40 Stalls when warm

    Hi boaterfun33,

    You should NOT run the engine in a bucket long enough for the water in the bucket to get warm! That may damage the engine. Buckets, trashcans or test tanks should only be used for a very short time.

    How long is safe is relative to how much water the tank or can holds. But, as a general rule, if you need to run in a tank more than a couple of minutes, you should be constantly supplying a cool replenishment of water to the tank.

    The reason is that the hot exhaust from the motor rapidly heats the water in the tank.

    If you run it until the water is hot then the outboard will overheat and eventually shut down. Each time that happens, it is likely that the engine is being damaged.

    If you continue having problems or need to ask more questions, please open a new thread. This thread is a year old and most people on the Forum won't see your posts and won't be able to help you.

    Good luck.

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