A moment of inattentiveness...

[Manny]

led to what I assume is the overheating of my 1998 Honda BF8 outboard. I after pulling into my slip and securing the lines I was talking to people on the dock, the outboard was still idling and after a few minutes I started to notice an odor like burning plastic. I glanced over at the outboard and noticed a very reduced trickle of water and could see it was running a little rough. As if that wasn't bad enough I swear I saw some smoke coming off the top. My wife and I shut it down. I took the cover off and it felt hot inside, I waited a while and tried to start it to see I could see anything and also run the fuel line dry. I took a lot of pulls but it did finally start and seemed to run okay, water was coming out at about a normal rate. I kept my hand under the stream and it was hot but not enough to burn my hand. I kept feeling the top of the engine and it actually got cooler the longer it ran.
I won't be able to get down until Thursday to check the oil and go completely over the engine but I am concerned that I may have done serious damage. I had a feeling this was going to happen eventually, the marina i'm in has a lot of vegetation growing in the water, as does my slip. The prop gets fouled and I have to clear it all the time. The water intake is small and I can see it getting stopped up pretty easily.
I'm wondering if anyone has had experience overheating a small 4 stroke outboard for a short period, and if generally the motor came through without much damage. Also if there is anything specific I should look for while going over the engine. A coworker said to definitely change the oil and check for water in it...

Thanks

Manny

 

[Rick Webb]

Impeller Change Coming Soon

Even if it looks OK it is probably stiff and likely to break at the most importune time.

 

[Manny]

Impeller was just changed in March

Rick, would running the impeller with diminished water flow cause it to stiffen up?

Thanks,

Manny

 

[Rick Webb]

Yep,

With no or just a little water running through it'll heat up pretty quick, the pump housing may be scored as well.

 

[oldiesrocker2001]

If you didn't run it too long that way....

Manny, Rick is right and you'll need to change the impeller(it's really the whole water pump but really small). My Merc had exactly the same thing happen while i was under sail in heavy chop and cross currents but kept the motor idling in case I needed it. The blades on mine felt mushy like gummi bears instead of stiff. You'll find that it's no big deal to replace if you're a DIY guy like most sailors, and I found that getting the tip-up lever adjusted just right took twice as long as replacing the pump. You'll want to do the job with the boat motor on a rack or still hanging off the transom rather than a work bench. Be sure to take note of the direction the rubber blades are bent on the old unit so you can duplicate it with the new parts. My motor survived just fine though I was really worried and babied it, which put a real crimp in our week on the lake, by running only momentarily until I could get it home

 

[BobM]

Impellers

You can wipe out an impeller pretty quickly. For the 20 bucks and fifteen minutes it will take to do the job I'd get 'er done.

 

[Manny]

Nice tip on the plugs

I didn't even think about the plugs. I'll definitely check those too.

Thanks for all the replies.

Manny

 

[RAD]

Another thought

I noticed that my outlet tube and my friends brand new Yamaha clogs up real easy with salt so we just clean it out with a piece of wire and all is well, but at first with water just dribbling it seems like a pump failure.

 

[Manny]

Went to the Honda shop yesterday

Got new plugs and ordered a new impeller kit. The guys at the shop told me the engine should be okay if it was only a short time overheating. Also since the impeller was only a couple of months old it should be okay. They told me about an outboard just like mine they have in the shop with a bad thermostat that they measured running at 290 degrees without damage! I asked what temp the engine should run and they said it should run about +/_ 160 degrees. I went to sears and purchased an infrared thermometer, got down to the boat, changed the oil - no water (whew) but it smelled a little cooked - installed new plugs (the old ones showing signs of overheating), then took the boat out. I ran the engine hard for over an hour while taking temp measurements. Most of the time it ran between 140 and 160 but sometimes it would go up to 180. Plenty of water streaming out the back, engine purrs like a kitten.
I got lucky this time.

Thanks for all the help,

Manny