Mercury Optimax Steam

[dennismtl]

{posted this over at THT but thought I would try here too...}

So I finally had my new to me boat out for a really good weekend of fishing.

One thing I have noticed is that after a hard run - 4k-5k RPMs for a few minutes (5 or 6) when I am coming back down to idle to come into the dock, there is a fair amount of steam coming out of what looks like the exhaust hole. I have changed the water pump and thermos (with the help of the great members here) so I am pretty sure those are not the problem.

Is it possible that on slowing down so water from the backwash makes it's way into the exhaust hole? The motor seems to sit really low on the back of this boat and the splash well is only a few inches above the water level so a fair bit of water comes in the well if i slow down too fast.

Open to any and all comments and advice - thanks in advance - getting used to this outboard has been a bit of a challenge for me coming from an I/O.

D

[berudd]

I don't know what causes this but mine does it and I've seen similar reports from others.

[gotaf7]

My 2012 150 does the same, always thought it was exhaust.

[maxl]

2010 150. Same thing for me

[Riccochet]

Normal. The engines cooling system water exits through the exhaust.

[SilverFox579]

Normal. The engines cooling system water exits through the exhaust.

^^^^

Completely normal.

[JOE54]

see those clouds in back ground steam will be worse in cool humid conditions

[bassnman81]

Mine does the same thin g too.

[EuropeanAM]

Completely normal. May vary from one 2.5L Optimax to another, but they WILL steam. Water is being dumped between and around the exhaust that exits the tuner (ie: 900 +/- degree F exhaust mixing with cold lake water). Hence the steam you see.