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BF100A over heat alarm issue

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Honda BF100A

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2016 Honda BF100A with just shy of 100 hours. Always fresh water. Been an excellent motor for me. I purchased used last year. No issues at all until spring Start up when I got an overheat alarm shortly after initial start up. I had a decent pee stream and water was 32°. I put motor in gear and as I advanced alarm went off. It would always return when I ran at idle or lowest trolling speed. NMEA 2000 said temp was 125°F. Thus began my journey with this problem. So far I’ve replaced impeller, both thermostats, flushed engine with thermostat pulled, and blown air into the pee tube. When I checked to see what code it was throwing I got a 27. Chart said that was the number two water temp sensor. I replaced that. Since then, my problem is much improved, but it has not gone away completely. I rarely see the engine temp go above 125, at wide-open throttle for more than 10 minutes it might creep up in the 140 range, but that’s about it. Now that it’s summertime and we’re dealing with 80° water. I still see the engine at 125F virtually all the time. Starts great runs good idles fine just that periodic temperature gauge going off is driving me crazy. Does this engine have a poppet valve? That’s the only thing I haven’t checked. Any help would be greatly appreciated.
 
Hi,

I'm really the wrong guy to be answering you but maybe someone like iang6766 can help. He's a pro outboard tech that works on lots of Honda models.

I tried looking up your outboard on boats.net but they've had an issue for YEARS showing the old 10hp models under the 100hp header and they don't actually show the 100hp at all. I have contacted them several times about the obviius mix up but they never do anything about it. I was hoping to find out if your model uses a pressure relief valve in the cooling system. When I have more time, I will try to look it up on a different parts site.

Question: Would you know whether or not if your outboard is at all similar to the 115hp model?

I ask because the 115 has 3 temperature sensors. 2 are located in the thermostat housing on the chain case and the other one is in the engine block

The stat in the block has the same part number as one of the two other stats in the tstat housing. That makes me wonder if some sorr of "conflict" or mix up could occur with a set up like that. It's a moot point though if your model isn't arranged the same way.

Sorry, not much help, I know.
 
No. My block is same as 75 and 90. Then they jump to 115 or whatever it is. My 2 thermostats are both on the side. Nothing on top. It is not throwing a code now. When I checked. Should have mentioned that.
 
Not saying your's is like this but the 90D has 3 thermostats. 2 in the engine block. One on each side....item 16 in link below


And one in the cylinder head...item 26 in the link below.


Probably diffeeent because yours is an A model but thought I would point it out just in case.

Good luck.
 
What if your water pump isn’t 100%, say the base plate or the cup is slightly warped or out of round? At idle you don’t have enough revs. to push enough water thru the water pump due to a weakness somewhere in the pump assembly. At higher revs. the volume is enough to overcome any issues with the pump and sends enough water to satisfy the ECM.
 
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