Logo
FULL SITE MENU

BF20 Headache

H

hondaheadache

New member
Hi, did a search through the posts hoping someone had a similar issue and fix but couldn't find anything.
My BF20 is run regularly, taken care of but has had issues with water in the fuel in the past. Carb has been cleaned a few times, put on a water separator filter, new tank, but have had persistent issues despite. Last week I installed a brand new carb assembly thinking it must be a the carb but unfortunately the problem persists.
BF20 manual choke and ignition

Context - starts first time always. Choke on for a minute then turn it off. Idles perfectly. Start to throttle and take off. Within 15-30 seconds...

Issue - outboard looses power. Runs rough. If I try to throttle it just hesitates then stalls. Oddly if I kill the engine and start it again it tends to run fine for another 15seconds them the issue occurs again. Kill the engine and start it again and it runs absolutely fine.

After a few rounds of the issue it will run really well. The only time the issue occurs again is when I'm fishing for maybe 20/30min and start the engine again. Occasionally the issues happens again when it's already warm, but not always. About 50/50.

It can't be the carb or the fuel. Both a A1. If it was the fuel pump wouldn't I have the issue all the time rather than when cold or restarting after a rest? Weirdest thing is how turning it off and on again actually helps... it's acting like a computer LOL

The only other thing I have noticed is that when I get the issue as it's warming up I usually get a bit off smoke come from the engine as it's loosing power. Not a huge amount and I never see the smoke if the issue occurs after a rest/when it's already been run.

Any suggestions would be great. Every mechanic I speak to just says fuel Nd carb issues but these aren't causing this. Many thanks 🙏
 
Check valve clearance.----Inspect fuel pump.-----You have installed a new impeller every 5 years or so?----Does spark jump a gap of 8 mm on both leads ?----Test run with another tank and hose as well.
 
racerone said:
Check valve clearance.----Inspect fuel pump.-----You have installed a new impeller every 5 years or so?----Does spark jump a gap of 8 mm on both leads ?----Test run with another tank and hose as well.
Click to expand...
racerone said:
Check valve clearance.----Inspect fuel pump.-----You have installed a new impeller every 5 years or so?----Does spark jump a gap of 8 mm on both leads ?----Test run with another tank and hose as well.
Click to expand...

racerone said:
Check valve clearance.----Inspect fuel pump.-----You have installed a new impeller every 5 years or so?----Does spark jump a gap of 8 mm on both leads ?----Test run with another tank and hose as well.
Click to expand...
Cheers will take a look. New impeller about a year ago and did new fuel lines when I swapped the tank under a year ago too.
 
hondaheadache said:
Cheers will take a look. New impeller about a year ago and did new fuel lines when I swapped the tank under a year ago too.
Click to expand...
racerone said:
Check valve clearance.----Inspect fuel pump.-----You have installed a new impeller every 5 years or so?----Does spark jump a gap of 8 mm on both leads ?----Test run with another tank and hose as well.
Click to expand...
racerone said:
Check valve clearance.----Inspect fuel pump.-----You have installed a new impeller every 5 years or so?----Does spark jump a gap of 8 mm on both leads ?----Test run with another tank and hose as well.
Click to expand...
Any idea what the intake and exhaust range is for those valves on a bf20dk2? Also when you say spark plug lead gap you mean the electrode gap right? Sounds like you're talking about something else
 
Sparkplugs are not used to do a proper spark test.----The question is simple.----Can your ignition system develop voltage to jump a gap of 8 mm , yes or no?
 
Not sure how to test that one. I plan to rule out what I can before taking this to mechanic again. Can you let me know why this seems like something to check? The engine runs perfectly when warm at all speeds. It's just when it's warming up or after a rest the issue happens. Interested in your thinking here
 
Valve clearance measurements as follows:

Intake--- 0.15 to 0.19mm
(0.006 to 0.007 in.)

Exhaust-0.21 to 0.25mm
(0.008 to 0.010 in.)

That's a pretty "fresh"...(as in new)....outboard so my guess is that the valves haven't worn very much. But, having said that, I think checking them every 3rd season is a really good idea.

This issue could be caused by water build up in the fuel chamber. Item 2 in the link below:


I recommend removing and shaking all liquid out of the fuel chamber at least once a year.

While these symptoms do sound somewhat like an electrical problem, with the shut off "reset" you describe, drying out the fuel chamber is still where I would start.

Use WD-40 on the holder and dipstick tube to aid in removal and refit.
 
jgmo said:
Valve clearance measurements as follows:

Intake--- 0.15 to 0.19mm
(0.006 to 0.007 in.)

Exhaust-0.21 to 0.25mm
(0.008 to 0.010 in.)

That's a pretty "fresh"...(as in new)....outboard so my guess is that the valves haven't worn very much. But, having said that, I think checking them every 3rd season is a really good idea.

This issue could be caused by water build up in the fuel chamber. Item 2 in the link below:


I recommend removing and shaking all liquid out of the fuel chamber at least once a year.

While these symptoms do sound somewhat like an electrical problem, with the shut off "reset" you describe, drying out the fuel chamber is still where I would start.

Use WD-40 on the holder and dipstick tube to aid in removal and refit.
Click to expand...
Yep I know. Have only had this thing for a few years and it's been a nightmare. It's probably had about 150hrs in that time so you've got to accept things need maintenance but this is something else.

Many thanks for the ranges. Will shake out the chamber this afternoon. Appreciate the explanation of how the reset solution ties in with electrical.

Quick question about the valves too. Do I really need to replace the gasket after checking it can I get away with reuse?
 
You should have no issue reusing the rocker cover gasket. It's a molded and high quality gasket that will likely stay in place when you lift the cover off.
 
jgmo said:
You should have no issue reusing the rocker cover gasket. It's a molded and high quality gasket that will likely stay in place when you lift the cover off.
Click to expand...
Thanks. Only had time to shake out that chamber. Also took off the fuel pump and it all seemed ok but I don't really have a baseline to compare against. Can I open that thing up? Noticed it's only sold as an assembly.

Took it out on the wknd and it only played up once and later in the day. I actually think it's all related to issue I notice when flushing it after use. I tested 3 times in a day. Each time leaving hours between trying again. On each occasion it idles for 3.15-3.30 then it instantly stalls. No gurgle or struggling before it stalls. Otherwise starts easily and sounds great when idling. Any ideas on what would cause that to happen so consistently? A fella at another mechanic said the bf20d can get a water block in a tiny passage that tells the engine it's overheating even though the engine is being cooled. Couldn't get any more information on that though. I don't hear any buzzer to tell me it's overheating and there's plenty of water coming out the tell tale.. but after the stall and a restart the water flow out of the tell tale slower for a minute until it picks up again. Still some pressure but about half as strong
 
hondaheadache said:
Thanks. Only had time to shake out that chamber. Also took off the fuel pump and it all seemed ok but I don't really have a baseline to compare against. Can I open that thing up? Noticed it's only sold as an assembly.

Took it out on the wknd and it only played up once and later in the day. I actually think it's all related to issue I notice when flushing it after use. I tested 3 times in a day. Each time leaving hours between trying again. On each occasion it idles for 3.15-3.30 then it instantly stalls. No gurgle or struggling before it stalls. Otherwise starts easily and sounds great when idling. Any ideas on what would cause that to happen so consistently? A fella at another mechanic said the bf20d can get a water block in a tiny passage that tells the engine it's overheating even though the engine is being cooled. Couldn't get any more information on that though. I don't hear any buzzer to tell me it's overheating and there's plenty of water coming out the tell tale.. but after the stall and a restart the water flow out of the tell tale slower for a minute until it picks up again. Still some pressure but about half as strong
Click to expand...
On the good news front the engine did get me to a favoured spot, about 10min ride away and managed to bag some decent fish 🙏
 
The fuel pump is non-servicable. It has to be replaced if no good.

Good you found a honey hole to fish but if the outboard is overheating and you keep using it like that, I'm afraid it won't be getting you there or worse, back home much longer. I don't know for certain but if overheating internally, each time it shuts down there could also be a little damage taking place.

Just my opinion but, based on what you're saying, I think it could very well be an internal overheating issue.

Is the green oil light on when it's running? If so, I think that it might do some good to remove the thermostat, test or replace it and and do a vinegar flush of the system.

If you haven't replaced the water pump impeller you might want to do that as well.

One thing you might try is to unplug the overheat temperature sensor and see if it still shuts off after that 3 minute 15 second mark. If it doesn't then that confirms it's shutting down due to the overheat protection circuit.
The problem then would be figuring out exactly why.

It could mean that the temp switch is bad.
It could mean that it's actually overheating.

I don't recommend that you run it with that switch unplugged fpr more than the 3 minute test.
 
Yep Green light is on the whole time. Correct me if I'm wrong but isn't there a buzzer that goes off when it overheats? It certainly doesn't smell like it's cooking itself but I hope I haven't been cooking it.

No idea where that overheating temp sensor is. I'll do some looking but if there a pic or something you can share that'd be great l. Will start with a vinegar flush give I spend all my time in salt water it's probably due. I did replace the thermostat about a year ago. Took that out and inspected - seemed fine. Also ran it for 10/15sec to check flow behind it with it out and it was fine.
 
My 20D shop manual indicates that there's no overheat warning lamp OR alarm on tiller models. Remote control only.
I can't say for sure since I've never worked on a tiller 20.

I don't remember exactly where the thermal switch is and I can't find an illustration of one..I also can't get to my outboard to look for it right now.

I do know it's installed in the cylinder head and has two wires going to the connector.... ....Green/black and red blue.
Sorry, that's all I can offer you at the moment.

The troubleshooting section says to jump a 100 ohm resistor across the connector terminals as a test of the indicator although I don't believe there is one on tiller models.

Not positive but I also think doing that might be something that would be valid to see how the control module reacts to that input.

That would also seem to indicate that the switch is normally open.

Good luck.
 
jgmo said:
My 20D shop manual indicates that there's no overheat warning lamp OR alarm on tiller models. Remote control only.
I can't say for sure since I've never worked on a tiller 20.

I don't remember exactly where the thermal switch is and I can't find an illustration of one..I also can't get to my outboard to look for it right now.

I do know it's installed in the cylinder head and has two wires going to the connector.... ....Green/black and red blue.
Sorry, that's all I can offer you at the moment.

The troubleshooting section says to jump a 100 ohm resistor across the connector terminals as a test of the indicator although I don't believe there is one on tiller models.

Not positive but I also think doing that might be something that would be valid to see how the control module reacts to that input.

That would also seem to indicate that the switch is normally open.

Good luck.
Click to expand...
Ah crap. From past posts I thought there would be an alarm. Think I found the sensor. Will try opening up the cooling side, clean out what I find and flush. Appreciate the input. Will report back when I find what's causing it all
 
Hi. Good news. It all seems to be caused by a half working thermostat. Ordered a new one with the broken water temp sensor and thought I'd check the existing one. Put old and new thermostat in boiling water and noticed the new one opened up about twice as much. After swapping out the thermostat and running salt away through it the engine is running fine.
Key symptoms were
Shutting down after 3-4min when flushing
Running rough after 1min of running (would have been the water temp sensor doing it's job)
After restarting running fine ( assume the faulty thermostat opened fully once the water stopped being pumped through)

Glad I didn't take it to another mechanic,. they all kept saying fuel pump, fuel issues or carby

Thanks for the help everyone
 
Alright! Yes! Good news for sure!

Goodonya for sticking with it and figuring it out instead of running it "to the death".

I know you said that you have had problems with yours but I really love my 06 20D and wouldn't trade it for any other brand. Ain't an outboard in the world that's "trouble free".

NOW! It's time to get back to that honey hole and have some fun!

Thanks for the update and explanation for your FIX.

Stay safe out there.
 
Back
Top