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BF9.9 white smoke but cool pee trail, and clean oil

W

will church

New member
Hi all

I had a problem with my bf9.9, it did get hot when the impellor fell apart and no one noticed it wasn't peeing. it did not stop running, run rough or sound an alarm (do they have one?), and when back in I replaced the impellor. It is probably about a 1995 engine.

The old impellor was nothing left but a stub, and the housing had some blockage from the fins, which i cleared out.

The engine still starts really well, runs with full power pushing the boat just fine, the pee trail is warm not hot (ie the right temperature), but at 3/4 to full revs it produces some white smoke that smells petrolly - not at start up or low to mid revs. it isn't loads but is noticeable.
The leg seems fairly hot to touch (but not too hot to hold, and i'm not sure if that is normal having never tried it) at these revs, and the cowling feels warm on the outside (not hot, but certainly warm). the oil hasn't gone creamy.

Could some of the cooling channels be blocked, causing some of the engine to get hot, and not others (including wherever the pee trail comes from) and creating steam? What is confusing me is that the enging is running really nicely without any complaints.

Really hope someone knows what this is or where to look!

Thanks

Will
 
Unfortunately, this motor did not have an alarm or an overheat cutoff.

The good news....it is a pretty durable engine.

Did you remove the thermostat and backflush back through the water tube to be sure that you got all the pieces of impeller.

Since it is running ok, the head gasket is probably ok, but you should check the spark plugs for any water droplets after you run it, just to make sure.

The most likely problem area is under the powerhead or at the exhaust. Check out part #18. http://www.boats.net/parts/search/Honda/Outboard%20Engine/0/BF9.9AK%20LA%20/OIL%20PUMP/parts.html
The water goes up through the small hole and the exhaust goes out the big hole of the o ring. If the engine gets hot, this part sometimes melts and causes leakage or might even melt and roll over to block the passage.

I am not sure if you can get to this without pulling the powerhead. I think, you can just pull the head. If so, then you will also need a head gasket.

If you pull the powerhead, there is a powerhead gasket and a couple of other gaskets.....I would also change the oil seals, which are easy to get to once the powerhead is off....since you are there.

A couple of thoughts....

I am sure others will have additional opinions.

Mike
 
Hi mike

really helpful, thank you.

Of course i didn't backflush it....of course next time this happens, i will think to do that. We live and learn. Presumably that would be a waste of time now as the new impeller must have spread the fins through the engine :-(

Looks like time to start stripping and see what pieces i can find. I think I will start at the exhaust and see what's there, and proceed on to the head if i don't find a substantial lump of fins.

Will
 
Hi will church,
Welocme aboard the Forum.
Mike is the "dude' here for sure so I would go with his input. I just wanted to say that the smoke colors come in a few "hues" but not white. Light blue or "grey blue" is oil being ignited because it gets past the rings. Black smoke is partially burned fuel from poor combution.

But, when we see white, it is either steam from water being heated in the combustion chamber or raw, unburned fuel vapor from NO COMBUSTION.

Since you plan on taking the engine apart, this "fine point" probably may not matter but I wanted to bring it up anyway. Also, you might consider doing a compression test and leak down test PRIOR to disassembly so that you might get a better understanding of what is happening. After you open her up, it will be too late to go back and retrieve this "intel".

Good luck.
 
As they say...hind sight is 20/20. If you still have your old impeller and pieces that you found....try to reconstruct the impeller. That way, you know what pieces you are missing and what to look for.

I agree with Jimmy on the compression and leak down test. If that is good, you may not have to disassemble the block. Maybe pull the powerhead and pull the head. That would keep things pretty straightforward.

Mike
 
hondadude said:
As they say...hind sight is 20/20. If you still have your old impeller and pieces that you found....try to reconstruct the impeller. That way, you know what pieces you are missing and what to look for.

I agree with Jimmy on the compression and leak down test. If that is good, you may not have to disassemble the block. Maybe pull the powerhead and pull the head. That would keep things pretty straightforward.

Mike
Click to expand...

Thanks guys - I think cobustion is complete, there is no lack of power at all or miss firing, but I will do the tests. Rebuild here we come....I think a winter job for me.
 
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