kicker spits unburned fuel

Rightbait · 12-13-2005, 11:42 AM

my 9.9 merc spits unburned gas out of the exhaust it's a 03, 2 cycle with below average hours on it.
i took it in for it's yearly tuneup, runs terrific, no problems, but was told that 2 cycles will spit a little(?)
my old 15 ran forever without ever doing that and i have not seen it on other kickers i've been around.
any thoughts? suggestions?
thanks!

BM-FISHER · 12-14-2005, 05:41 PM

I have seen this on many merc. 2 stroke kickers.

Okie · 12-14-2005, 09:06 PM

I'm not sure how you know it is spiting out unburned gas as the exhaust is normally under water. Are you positive it is unburned gas and not water droplets that smell like gas??
Good Luck.

1pump · 12-15-2005, 11:10 PM

The main exhaust is under water (thru the prop hub) but the exhaust bypass is above water. The bypass is for idle speeds, when there isn't enough exhaust pressure thru the hub.
When you say it spits out the exhaust, I assume you mean the bypass.
My Merc spits water out of the bypass, but no gas.
If it were spitting straight gas out the bypass, I'd think you'd have bigger problems, like a motor that barely runs because it's too rich or flooding.

It might spit some out if you run it out of the water, like during a flush, since there's no backpressure on the exhaust.

Rightbait · 12-16-2005, 08:54 AM

it is spitting out of the bypass port it appears to be fuel it will leave that rainbow sheen on the waters surface.
the motor runs very well at idle and at all levels of rpm, does not miss or stall.
still not sure what to think.

ET · 12-16-2005, 11:19 AM

All two-strokes spit "a little". Now define "a little". My old two-stroke would spit "a little" now and then. Maybe yours just needs to be taken out and run hard for a while to clean everything out.

Another thought is that the motor is just designed that way. I had a 70hp Johnson that would spit "a little" fuel at idle. I read up on the carbs for that model and learned that there really wasn't a good way to adjust the fuel mixture at idle. The motor was just designed to run inefficiently at idle and spit a little fuel. I would have thought a 2003 would be much better though.

Has the motor always done this? If the mechanic says it is okay and it runs well, I wouldn't worry too much. The new four strokes sure are nice though....