Strange behaviour BF15d

Hello,

We have bought a slightly used BF15D last year, we use it for 14 days every year. The first year everything was smooth until the very last day where the engine couldn't keep running at low rpm and stalled. Was hard to start. In order to clean the carbs, I used some injector cleaner in fuel and tried choke at full throttle to create vacuum at intake to suck debries out of the nozzles. This seemed to help a little but didn't have a chance to observe it too long.

This year we ran the engine on the last year fuel mixture (with the cleaner) and it run quite well but there were still some misfires at low rpms. We refilled fresh gasoline and used the cleaner again and the things retured to the bad side. Once again the engine is hard to start and stalls from low rpm, but idles and revs at high rpm just fine!

I tried to keep the prime bulb upwards but I noticed that it drains the gasoline back to tank when the engine is not running and is quite empty when it is running. But it is possible to reach hard state when pumping manually. Even with manual pressure it does not affect the engine run though. I guess it is good idea to replace the hose with bulb, but it will not solve the issue with misfires/stall at low rpms as it is not affected by manual pressure.

Any ideas guys? Thank you!

1. get rid of all the gas, and run fresh gas every year. At the end of use, when it is store for 1 month or more, drain the carbs.
2. Replace all the fuel lines, internal and external including your primer bulb, if it is draining back, it is shot. If you bought it used, the exposure to sunlight extra is unknown, about every 3-5 years depending on sun exposure its good measure to change them out to avoid breakdown and air leakage.
3. Check and tighten or replace all fittings on fuel lines, once you replace the lines.
4. Replace the inline fuel filter.
5. Drop the carb and clean it. or replace it. I would opt to buy a new one, and then drop and clean your old for a backup.

When possible run ethanol free fuel.

eneusiis said:

1. get rid of all the gas, and run fresh gas every year. At the end of use, when it is store for 1 month or more, drain the carbs.
2. Replace all the fuel lines, internal and external including your primer bulb, if it is draining back, it is shot. If you bought it used, the exposure to sunlight extra is unknown, about every 3-5 years depending on sun exposure its good measure to change them out to avoid breakdown and air leakage.
3. Check and tighten or replace all fittings on fuel lines, once you replace the lines.
4. Replace the inline fuel filter.
5. Drop the carb and clean it. or replace it. I would opt to buy a new one, and then drop and clean your old for a backup.

When possible run ethanol free fuel.

Click to expand...

Hello,

Thank you for the tips. Today I bought a new hose with bulb and connector and new transparent fuel filter. It can be clearly seen, that there is some problem with fuel feed, because the filter can be filled manually by the bulb but is almost empty on the run any ideas?

Thank you!

Ps: Tank filter checked and is like brand new

Please see the video. If I manage to rev it, the filter is even emptier. You can see it stall if I apply slight throttle from idle.
https://youtu.be/Aw1H9zHztg0

That's perfectly normal, no filter on any outboard remain completely full because there is negative pressure in the fuel line, same applies to the primer bulb, they do not stay firm under normal running conditions. Just give the carb a good clean and it will be fine

Ian is correct....as usual....

...you won't see the filter full of gas while the engine is running. It sort of "burbles and gurgles" and will look "weak" on fuel flow but that's just how it works.

The 15D is a very simple engine and idle issues are almost always carburetor being dirty in the small (tiny actually) passages.

These carbs are VERY susceptible to mineral deposits and fuel contaminants especially if you don't drain the float chamber prior to long term (a month or more) lay up. And, they can be difficult to get clean for the inexperienced mechanic. You will NEVER get one "right" without a total cleaning regimen as described in the HONDA MARINE CARBURETION MANUAL

Just wanted to give you a second opinion so you are positive about what direction to take and know that all of Ian's suggestions are pertinent to what you are experiencing.

Good luck.

Hello guys,

Thank you very much for your help! Today I did a very precise cleaning with help of my toothbrush, metal wire and carb cleaner. I sprayed every hole and passage intensively, removed all the nozzles etc. Also drained the fuel container. There was a serious amount of mineral deposits in the corner of float chamber and pieces of some assembly glue around the chamber seal which I cleaned.

I was still quite sceptical, but couldn't be happier after first start It runs like new!

Thank you!

Good news!

Now, always use fresh fuel and keep float chamber dry during storage/lay-up and you won't have that problem for a long time to come.

But how do I empty it easily?

Honda provided a drain screw on the forward side of the float bowl. They also provided a small hose that carries the fuel out to a drain nozzle (located next to your water pump tell-tale nozzle) on the starboard engine cover.

You will probably need to find a long, slot type screwdriver that will make it easier to loosen the screw. I have a screwdriver for draining these carbs that I got especially for that chore.

The good news is that you only need to loosen the screw....not remove it....to drain the bowl.

Honda set it up this way for a reason. Find that screw, use it and your carburetor problems will not soon return.

Good luck

Is it this one?

Well, it should be on the bottom of the float chamber but it looks higher up in your photo. But it does look like a drain screw.

I don't see the later year models these days so, depending on the year of manufacture, perhaps they've made it more accessible. If so, that's a nice touch.

Short answer??.....I'm not 100% sure on this one.

Yes, that is the drain screw

Ok, thank you guys. Today was the last day of my vacation. Was little bit in hurry so i didn't drain it using the screw, but let it run out of gas. Ran almost two minutes without the fuel hose connected, so I hope all the gasoline in burned and I won't get any problems next year... Thank you once more!

That will be fine, the little remaining will evaporate

Nope! Not good enough! You DRAIN it for a REASON!
YES, the "remainder will evaporate" and leave behind any minerals that were in the fuel!
It will probably start and run ok next season but it will have that little "coating" in there.
Keep doing the same thing and it won't start or WILL run like CRAP.



AGAIN!

You can lead horses to water but you can't make them drink!

SHEESH!

I'm done here

Hello guys, leaving in an hour. In meantime of loading the car I jumped to the garage to drain the remainders. I loosened the screw by maybe 10 turns and not a single drop appeared. I guess you are right about the deposits, but it seems the amount of remaining fuel was almost the same as if I drained it using the screw. Still the amount of minerals in remaining 2ml of fuel is less than in a carb full of fuel (like last time). Next time I will use the screw though. Thank you.

Yes, use the drain. "Running the carb dry"is hit or miss at best. The drain is a SURE thing allowing you to know, without a doubt, the carb is empty.
That is, of course, as long as the drain hose is correctly routed, not pinched or kinked shut and the nozzle is clear. People routinely get the tell tale and drain hoses in a bind when replacing the side covers.

Good luck.