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Honda BF20 overheat warning

S

Sarrre

Contributing Member
Hi there, I'm from Sweden and this is my first post here! Hope you can help me with this problem.

I got a Honda BF20 with remote control and powertilt. When running at trolling speed the buzzer is warning for overheating. However there is a good stream of water coming out, and the engine cylinder head is not feeling very hot. I may think it is a false alarm because it does never warn for overheating when I run the engine at full speed. ONLY when idling at trolling speed, and then after about 30 seconds it shuts of by itself because it thinks it is overheating. Someone recognizes this problem? Is there a sensor somewhere that needs to be replaced?
 
There will be a thermoswitch on the block. It will look like a smallish round button with two wires coming out from it that is held against the metal by some sort of bracket (sorry, I'm not that familiar with Honda's) Generally you test this switch by putting it in water then hooking it up to a multimeter. As you heat the water the switch should come on at a certain temperature and then off at a different (lower) temperature. For my motor those temperatures are around 80 deg C and 70 deg C for activate and deactivate respectively.

Stuart
 
Your thermostat may be stuck closed or clogged.

Pull the thermostat out and run your engine at idle speed without the thermostat and with the thermostat cover off...just for a very short time 10 - 15 seconds.

There should be a good flow of water shooting out of the opening about as big in diameter as the thermostat hole. If it just dribbles, then you have problems with you impeller (maybe missing parts of the impeller tips) or you might have picked up some sand or debris with is partially blocking the path that the water takes through the head/block going to the thermostat.

If the flow is good....put the thermostat cover back on without putting the thermostat back in and do a test run. Without the thermostat, the engine will probably not idle like it should, because it is not getting to proper operating temperature. So, do not run it this way for a long time....just long enough to prove that it is or is not the thermostat. You can stick the thermostat into heated water to check, but this is a much quicker way and it will also tell you the strength of the water flow.

Mike
 
I will add to this rather than start a new thread. The OP never mentioned if they fix their problem

This will be for Mike @hondadude hopefully

I have the same issue as the OP.

Motor runs fine, at idle however after 3-4mins the overheat alarm comes on.

Background:
  • This is a 2014 BF20D done 200hours in the SALT.
  • Been in storage for a year. Was flushed prior to storage.
  • Been out of storage and I have done a complete service; water pump impeller kit put in, oil, fuel filter, plugs, thermosat working fine cleaned carb etc etc.

NOTE: I did start it prior to changing the impeller and it ran BUT the impeller gave up eventually. When I replaced it, it had shredded. I got a few of the bits out but likely not all.

Now I get this problem. Setting the idle to 1000rpm negates the issue but RPM is meant to be 400 and when I adjust it for that, 3mins and the alarm comes on.

I have tested the thermo sensor and it is working, 250ohms after running.

I have removed the thermostat and started engine as Mike aka @hondadude mentions above. What I get is NO FLOW on idle. Plenty coming out the pee pipe at all rpm ranges.

I have put a hose in the thermostat hole and flushed it back with a hose with the bottom end (gearbox) off. Flushed with as much pressure as the hose would allow which was a fair bit. Didnt help.

Another question: What is the purpose of the "flush valve". Its not attached to anything for "flushing".

Where to next? Take the water jacket off and see how bad the deposits are in there?

Help.
 
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You need to replace the whole waterpump kit, if you look very close you will find it has got hot (shredded impeller) and the liner is not sitting flush making the pump inefficient. Part number 06193-ZY1-010
 
iang6766 said:
You need to replace the whole waterpump kit, if you look very close you will find it has got hot (shredded impeller) and the liner is not sitting flush making the pump inefficient. Part number 06193-ZY1-010
Click to expand...

Thanks. The liner and certainly the metal plate looked scored on the edges.

I will give that a whirl. Much appreciated.

Would you know the part number for the water jacket cover o-ring (page 11-2 item 5 in the service manual)? May be 19371-ZW9-000
 
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Yes, just not for long, run until it goes into gaurdian, stop and disconnect the sensor, do a short run to see if the problem had gone. I found 99% of these overheats are in fact overheats, blocked head or exhaust plate galleries
 
Can I jump in here? I’m new to forum. I’ve been on a long journey chasing an overheating problem and rough starting problem. Got everything working beautifully (new carb, impeller, all cooling outflow clear including telltale). Ran for 5 minutes, I was in heaven. Put the lower covers on and now won’t start. Ideas? 2017 Honda outboard bf15d.
 
Go back to basics, spark, fuel. Covers can't have anything to do with it unless you crush wires, which is also highly unlikrly
 
One mechanic pal thought it might be the stop switch. I tested and it works fine. Another mechanic thought that my conclusion that I was getting no spark may be false because the spark is really hard to see and the motor is outdoors. I’ll test under a blanket tomorrow and report anything useful I discover. I also intend to test the thermo sensor wiring for continuity. One side note is I’m having a lot of trouble tracing wires around the harness etc. My motor is a 2017 model.
 
Well, I checked the spark under a blanket and it was there, so I’ve been chasing the wrong scenario! I did observe something interesting before I checked the spark, namely that measuring resistance across thermo sensor showed it as an open circuit. The temp was around 50 degrees.

So back to my strange problem, why did my motor fail to start after I installed a new carbuerator and ran fine for 5 minutes. When all I did after running it was spend half an hour putting the lower covers back on.

As the other commenter said, start over. I will, but any ideas what to start with would be appreciated.
 
If you have spark and it won’t start, you are likely lacking fuel. Try pumping the bulb until it is hard, then try to start it. Report results.
 
Ok, I disconnected fuel hose after fuel filter and squeezed bulb: got fuel. Reconnected then disconnected fuel intake to carb and squeezed bulb: got fuel. Then pushed starter … and did not get fuel. Figured problem might be fuel pump. Reconnected and pushed starter … and it ran! Put covers on. Not confident that I’m out of woods.

So what was the original problem? One thought is that when I pulled fuel tank filter to check for clog, that caused an air bubble in fuel hose. Credible? Also, should I have expected to see fuel dribble out of the hose when I pressed the starter with carb intake hose disconnected?

In any case, thanks for jumping in, it helped. I may be back if problem resurfaces.
 
I’m baaaack. Ran fine for a while and then again the next day. Then tried to start and no go. Thinking maybe vapor separator (aka fuel chamber) between fuel pump and carb. Will try to clean or replace. Thoughts?
 
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