Honda BF20 20 hp 2004 motor keeps dying at low/idle speeds

[pikie]

Hello, I've got an issue with my motor (BF20D4LHA) that has stumped myself and my mechanic for 3 years now. I've checked here

Symptoms:

Motor starts fine (manual start). Will idle for quite a while without trouble. Operation is good at any speed other than idle. If I run for a while, and let it idle it will eventually die. Just sounds like I hit the kill switch (no rough running). It restarts easy, but will die again after about 1.5 minutes (I've timed it before, its always around 1 min, 40 seconds). If I try to troll with the motor (this is a fishing boat), it keeps dying like this making for a very annoying day.

Once in a while, the motor does get stuck in a strange surge mode, where it revs up and down, only when trying to take off from idle. It almost never "works thought it", but is always fixed by killing the engine and restarting.

What my we have tried: (my mechanic was a certified Honda mechanic, he still works on them on the side)

Dissemble and ultrasonic clean of the carb. Same issue. Bought a brand new carb and installed, same issue.

Turned idle up some, same issue.

New fuel filter internal and in the external gas line. Built a new gas line, took tank apart, inspected and put back together, same issue.

Found ideas of the fuel chamber on this site, removed, cleaned, dried off and reinstalled, no change.

Checked the spark plugs for fowling, they look fine.

This spring I invited my mechanic to fish with me so he could hear, see the issue first hand. We tried running without the cover on (to help air intake and rule out an exhaust leak inside possibly), manually squeezing the bulb to see if I could keep it from dying after the 1.5 minutes, no luck (to rule out the fuel pump I think, even though he thinks fuel pump problems manifest at high speeds).

I'm stumped. Any ideas? I've seen a post on this site about a scored impeller plate causing overheating. I see the ICM Unit and the ECT Sensor on this motors wiring schematic. If there was a overheat situation, would it just kill the motor, or would there be an alarm?

Thanks

 

[ahicks]

Does it act like it's hot? How warm is the water coming from the indicator? Solid flow, or kinda weak?

When was the last time the water pump was changed?

 

[pikie]

It doesn't act or feel hot, no. On the temp and flow of the indicator, I'll take it out tonight or tomorrow to confirm. I had the impeller replaced last fall, but I don't think I've ever replaced the whole pump. Thanks for taking a look at my long post!

 

[pikie]

Took it out last night. Steam might be a little weak at idle, but the temp of the water coming from the indicator is just barely warm. I took some videos to show it dying, at wot, and I even got a few seconds of the 'surge' I mentioned, but it died only 5 seconds after getting the video started, there is wind noise, but you can 'see' it surging. It was in reverse at the time. This is a web album with the 3 videos in it, it should be shared to the world, but let me know if it does not work (I have to view the actual videos in chrome to get them to work).

Use this link, the add link option seams broken to me, and now it won't let me remove it.

https://photos.app.goo.gl/ShYxaVURcFeSUXQv7

 

[ahicks]

I don't have a lot experience on the Honda's this size, but that "dribble" coming from the pisser looks WAY too weak in that video. Your "mechanic" should have picked up on that. It might just be plugged, the impeller may be shot, or if this engine is used frequently in salt water, it may be corroded/plugged with silt or something else.

That's where I would start anyway. That output should splash when it hits your hand....

 

[pikie]

Ok, sounds good, I'll try that and report back in a few weeks. No salt water use, but I did burn up an impeller once, so maybe the plate is scored and the only time it pumps hard is when its running fast.

 

[pikie]

I bought the whole impeller kit, housing and all just in case. When I took the old one off, I found 2 chunks of rubber from the last impeller job i did (the impeller in there was in good shape still). These chunks must have hidden on me during that job. Once I got it all back together, the tell stream is strong at idle. Took it out a few times so far and NO dying yet. I'd like to run it all day before I call this pesky issue fixed, but i'm optimistic. Thank you for the great advice.

Old chunks: https://photos.app.goo.gl/amkRBudsbEp9uQu36

New idle video: https://photos.app.goo.gl/sbrqYroZdyRJBqqQ9

 

[ahicks]

Best of luck, and thanks for getting back with your results! -Al

 

[raczekp1]

did you dissaseble cylinder head to clean valves and change valve seals?
valve lashes can be worn

 

[pikie]

did you dissaseble cylinder head to clean valves and change valve seals?
valve lashes can be worn

NO, I never messed with the valves. Beyond my ability so far.

UPDATE: Motor is working great now. I guess the lesson learned is if you cook an impeller, it might work after putting a new kit in it, but you might have damaged the housing like I did and will not get the same cooling as you should.

Thanks to the help fixing this pesky problem!

 

[kokes]

NO, I never messed with the valves. Beyond my ability so far.

UPDATE: Motor is working great now. I guess the lesson learned is if you cook an impeller, it might work after putting a new kit in it, but you might have damaged the housing like I did and will not get the same cooling as you should.

Thanks to the help fixing this pesky problem!

I came across your post on stalling bc I had the same problem. When I removed the lower unit I found 2 broken tabs on the impellor. I replaced it went out and the engine ran perfectly. Thanks