Honda BF0 probably overheating

"I have a problem with my BF10. It will start up as normally, will idle and go into gear without any problems. . But then after a minute or so it will loose all its power and it will wiggle when I give it some gas. Then it will idle but cuts of shortly after. But when directly starting the engine again, it will again run for a few minutes, like nothing happened and then cuts out again. I cleaned out the carburetor, as a preventive measure, but the problem persisted. I noticed that the engine is getting quit hot( especially the valve cover) , so I blew out all the water passes(because the tell tale was pumping a good stream of water, so it wasn't the impeller). The problem stayed the same. Then I ran the motor without it's thermostat. The motor got a lot cooler and would ran for a longer period of time. So I bought a new thermostat. But after running it at slow speed for about an hour it had the same problem again. Then I removed the thermostat because I needed to get back home. I still kept cutting off, even though the thermostat was not in place. I decided to let the motor sit for 15 minutes (even though it was not that extremely hot) and was able to get back home (about 1 hour without any problems).


Back home I tried two things. Letting the motor run with and without thermostat. With the thermostat the engine would heat up pretty quickly and cuts of within 2 minutes (when revving it a little bit). Without the thermostat the motor seems the stay cool, but apparently still cuts off when letting it run longer. I am pretty sure the thermostat is good (put it in warm water and it opens all the way)


One strange thing I noticed is that the tell tale will remain cold, with or without the thermostat, but when blowing air through the one of the passes at the end of the water housing it will blow air out of the tell tale, so I suppose also warm water would come out there.


Is there maybe someone who could help me out, but I do not have a clue at all. I read some stuff about a broken oil pump, which could also cause overheating, put I have no clue how to check this"

What year is your outboard? If you don't know, what's your best guess? Are you the original owner or, if you bought it used, how long have you owned it?

Did it run great before this? If so, did this problem start suddenly or come on gradually?

When was the waterpump last serviced?

Do you mostly use it in salt water and, if so, how do you go about flushing it if at all?

The more history or operational "back story" you provide, the better the guesses folks here can give you. I would be interested in how the thermostat cavity looked. Was it caked with salt or corrosion?

I'm the second owner of the outboard and I bought at the beginning of this summer. It is a 2005 model. The whole engine was serviced last winter including the impeller. It ran without any problems since I bought it and used it very often since the purchase. I only use it in fresh water. The problem came out of nowhere. After running for more than 3 hours at low speed it suddenly got this problem described above

jgmo said:

What year is your outboard? If you don't know, what's your best guess? Are you the original owner or, if you bought it used, how long have you owned it?

Did it run great before this? If so, did this problem start suddenly or come on gradually?

When was the waterpump last serviced?

Do you mostly use it in salt water and, if so, how do you go about flushing it if at all?

The more history or operational "back story" you provide, the better the guesses folks here can give you. I would be interested in how the thermostat cavity looked. Was it caked with salt or corrosion?

Click to expand...

Well, as long as you purchased it from a trusted friend or relative you might rely on the "completely serviced last winter" story. But, if not, you can't.

Ever changed the oil? Ever checked the gear oil level?

Is the green oil lamp on when running?

My take on your description of what's happening is from very far away and with very limited info so...I could be WAAAY OFF. But here goes:

Your instincts are good and pulling the Tstat to see what would happen was a good call in my opinion. It DID make a difference after all. Running the engine "cooler" will tend to richen up the fuel mix even if in not a very efficient manner.

I can only assume that you have possibly a fuel delivery issue and possibly a cooling issue too.
Not sure about the latter since you haven't actually measured anything. I suggest that you invest in an inexpensive infrared temperature gun that you can check engine temp with. You should avoid running the engine at elevated temperatures to prevent permanent damage.

If the green lamp is lit while she's running then forget about the oil pump thing. Not a common failure on these at any rate. Does your engine have a replaceable oil filter? I couldn't find a good description of the 10hp and only have experience with the 8, 9.9, 15 and 20hp models of that era.

It sounds as if the outboard is running LEAN on fuel. Running an engine lean WILL cause it to run HOT. The engine needs a good supply of gasoline to help cool the intake and combustion chambers.

You say you "cleaned out the carburetor" but I have no idea how you accomplished that.
But, even so, if the carb were brand new the lack of fuel could be because of something else.
The suction side of the system will pull in air if it develops a leak. The "usual suspects" are the remote tank hose, primer bulb and, often, a worn out disconnect fitting at the engine cowl or on the end of the hose....or both. Check that connection carefully. Smoke from a cigar or cigarette can be used here to blow through and find pinholes in the system.

The remote tank vent is another problem area for fuel starvation. People forget to open them or don't open them all the way. They will also simply vibrate closed on their own and can be clogged with airborne dust. People that store the boat indoors simply forget about closing and opening the vent entirely.

In addition to the tank and feed hose there is a small fuel filter that almost never clogs and the fuel pump that seems to last forever. But, keeping an open mind about what MIGHT be causing a problem is always a good practice. If you disconnect the fuel line at the carb and pull the engine over with ignition disabled, a small amount of flow out the line will indicate that the pump is ok. It's sort of a "gurburble" for lack of a more technical term.

Back to the carburetor. ....They aren't complicated but can be VERY finicky about how they need to be cleaned and cared for. If you let them sit without draining them or use old or "iffy" fuel, they WILL cause you grief. While Honda builds a FANTASTIC outboard, the little carburetors usually cause about 80% or so of the "headache factor" associated with owning one. Careful fueling and COMPLETE draining of the carb, especially before storing longer than a month, can mitigate this nuisance for the most part.

Just so you know, most "newbies" attempts at getting them clean are usually unsuccessful the first...second...third... and more times. They have "air jets" internally that many "pros" don't even know about.

As far as trusting what you were told about "complete service", DON'T DO IT! Think about it. Is someone preparing to sell an outboard going to put more cash than necessary into it prior to the sale? Even if the guy is your best buddy, he probably threw a new impeller in the pump and called it done. He doesn't think he's "getting over" on you and isn't lying. Pump WAS serviced, right?

Since your problem COULD BE twofold here...carb AND overheating...I strongly recommend that you go ahead and install a COMPLETE WATERPUMP KIT.
BECAUSE...
putting a new impeller inside a worn pump cup is like putting lipstick on a pig. At best you will only achieve a percentage of the efficiency that a completely new pump will provide. The tell tale is only a bypass that indicates the water is being pushed but, depending on your experience, what looks great to you might not be gettin'er done.

I'll stop now as I know it got "wordy"

Let us know what you think and do and find.

Ask all the questions you like.

Good luck.