BoatBanter.com - View Single Post - oil bubbles in exhaust in Merc 20 outboard?

On 15 Jul 2004 10:49:20 -0700, (tom clark)
wrote:

On starting and after about 5 minutes idle my Merc 20 outboard has
thousands of tiny oil bubbles coming out of the exhaust below the
water line.
Is the mixture too rich? too much oil ?( 50:1), head gasket ?( runs
fine).
Thanks

Idle mixture too rich??
Exhaust sludge from a previous years of service blowing out?
Incorrect timing/plugs?
Poor compression?
Low quality 2 stroke oil?
Faulty thermostat?

The list goes on, but a 2 stroke will never burn all the gas while
both the inlet and exhaust ports are both open. Unburnt (unburned)
oil, along with unburnt gas will always be present in their emissions.

As far as possible, let's keep our waters clean, for our Kids' sake.