Four Stroke Question

[Snake334]

I have a 2015 Mercury 150 four stroke. It has approx 20 to 30 hours on it. The other day, I noticed when I started the engine, it shot out black soot looking stuff from the upper exhaust / relief port. It only done it during start-up and I only noticed it 3 or 4 times over several days. The engine started normally and ran great. It made no strange noises or anything odd. I use a combination of 100% gasoline and 10% ethanol gas. I also use Stabil in every fill up. My question is, is this normal or is it a sign of a problem.?

 

[Scott Danforth]

all motors need to run rich when you first start them. when they run rich, they generate a bit of soot.

no need to use stabil every fill up if you boat often

 

[Snake334]

Thanks for the response. When we purchased the boat, the dealer said the Stabil was a recommendation from Mercury on their new engines. Use at every fill up, 1oz per 10 gallons.