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Bf50d won't stay running

J

JBC

New member
I have a BF50d on my pontoon with maybe 250 hours on it. It starts fine, idea smooth for about 8 to 10 minutes then does. Then won't start back up until I wait about 30 minutes. Will idle again for just a couple minutes then does. Mechanic said it needs complete rebuild. Really? Said it has low compression but I don't trust his word just yet. unit runs fine at idle, this happened all the sudden. Hasn't overheated. Replaced fuel lines and filters. Just don't want to pay 4K for a rebuild. I'm gonna pick it up and do my own compression check, but I just don't see how it could go low and still run good all the sudden.
 
Hi,
I agree with you. I wouldn't trust what he said either. And, I highly doubt that it could have low compression after only 250 hours unless it was overheated or run with no oil or badly abused in some other way.
Engines with very low compression or that are "worn out" usually won't start and idle then run good for several minutes like you say yours does.

Right off the jump, two possibilities for what you're describing come to mind....

The first is that there could be a problem with the fuel tank venting. If the tank vent isn't allowing the tank to equalize, the tank will go into a vacuum and the low pressure fuel pump will lose prime. Try running with the fuel cap loose or off to see if the condition improves. Just be cautious about spilling gas and possible fire. Don't lose the cap!

There's also a vent for the VST float chamber and it might cause this if it gets plugged. The problem is, I've never worked on a 50D so I can't tell you the best way to check for that.
But, maybe you can figure it out on your own. See items 23, 24 and 36 in the link below.


Then check out items 2, 9 and 19 that connect to the vent T in the link below.


Something else that might cause this is simply water in the fuel.

If you let the tank sit still and level for about 20 minutes, any water will separate and sit at the bottom of the tank. Take a sample from where the pickup tube does with a turkey baster and place in a clear container for examination.

Also, if you have a fuel/water separator, you should service it frequently and keep it drained.

Those are just a couple of ideas and hopefully others here will offer some more.

Good luck.
 
According to the mechanic, the computer senses low vacuum and shuts down after a few minutes. There is no Honda people anywhere near me. I'm picking it up from the mechanic on Tuesday. Contemplating getting a diagnostic tool for the engine. I've rebuilt every engine, except for an outboard, ugh. Im thinking it could be a computer problem, but first I'm checking everything mentioned above. Thanks, I'll post updates.
 
Yes, get your outboard away from that dude asap and don't go back!

Take your compression test....take out all spark plugs and either jump the starter solenoid or, if cranking with the key, pull fuel pump fuse....and....don't forget to open the throttle all the way.
You will then have a baseline of information to work from plus you will be reassured that the engine doesn't have low compression.

Does your remote console have the green oil lamp and red overheat light?
Is the green lamp lit when the engine is running?

You say it's never overheated. How are you determining that it's not? Do you have an infrared temperature gun?
Does it have a good pee stream?

It's best to assess the pump operation and cooling by placing the leg in a tank (trashcan) with water well above the anti ventilation plate...4 inches or more...rather than using muffs.


The computer is designed to de-power the engine and then shut it off if an overheat condition is detected via the engine temperature sensor. Those sensors can fail and give false readings.

I don't have enough information or any experience with one of these to guide you through troubleshooting but I agree that having the diagnostic software (Dr.H) would be desirable and would also want the shop manual for specifications, procedures and service information to work on this sophisticated outboard.
Guessing, throwing parts at it or making a mistake can cost you a BUNCH of money so please cautious.

Good luck.
 
You may have the same issue I had with my 60. If its fuel injected you may want to check the rubber grommet inside the VST. It takes a bit to get to the VST but I made a youtube of it. Mine would start fine then after I shut if off it would not start up until cooled off. Turns out the fuel was restricted by a faulty grommet that swells and covers the orifice.
 
Wow!

What a GREAT suggestion!

I knew about that grommet causing problems but totally spaced on it. Just shows how VALUABLE experience can be!

I hope JBC sees this.

Thank you jermbox for your post and the video!
 
Well, I picked up my boat and pulled out the VST. It was dirty, and the grommet on the fuel pump didn't look right. I trimmed it as directed in this post. Cleaned out the fuel pump really good. Just had the boat out yesterday for over two hours. Ran great. Thank you all for the excellent tips and advice.
 
That's great news JBC! Glad you got it fixed and thank you for posting the solution. It's no doubt to help someone else with that issue.

Happy 4th of July!
 
I want to add that during this repair, I thought I would replace the fuel filter with an aftermarket pump. It would run for about half a second and then shut off. I should have listened to other advice that aftermarket pumps use much more power. Put the original back in and, son of a gun, runs like a top. Don't mess with these aftermarket pumps.
 
JBC said:
Well, I picked up my boat and pulled out the VST. It was dirty, and the grommet on the fuel pump didn't look right. I trimmed it as directed in this post. Cleaned out the fuel pump really good. Just had the boat out yesterday for over two hours. Ran great. Thank you all for the excellent tips and advice.
Click to expand...
Glad to hear it is all fixed up! Another grommet issue, a huge oversight by Honda in my opinion.
 
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