I can tell you that the vent is there so that exhaust gases and water can vent when you are in REVERSE, as typically they are exhausted via the thru-prop exhaust channel.
But I cannot tell you if this is 'normal'. I'd call your dealer. But you'd need to adequately describe the condition and what you are seeing. Diagnosing boats and motors over the phone, mano to mano, and even through cyber-space is tough, as what one may see and/or interpret - may be an entirely different thing altogether.
Example: A guy from my boatclub had a new-to-him used 90hp installed on his boat, after buying a used motor from a local dealer. He tells me it sometimes 'stutters' while up on plane. He asks me to look at it. I'm traveling and knew who installed it, so I say "Take it back where you got it." He's too lazy ... would have to take the boat out, put it on a trailer, trailer to the shop, and wait ... yada, yada ... so he continues to run it.
Then he calls me over the other day while I was on the water and complains "It's still doing it, but almost all the time now - it's worse!" So I tie up my boat and jump on his. 50' out of the No Wake Zone I put the boat up on plane. BANG! Sounds and feels like the boat hit a log! He says "Yup, that's it, that's what it's been doing!" I immediately take it off plane after only happening once and tell him ... that's the motor coming out of gear @ 3500+ RPMs and then slamming back in ... I told you should have brought it back IMMEDIATELY - as that is not a 'stutter'!
Turns out he blew the lower unit gears, to a tune of a $1200 bill. While the dealer improperly set-up the controls, my friend has zero recourse, as he continued to run it for almost 2 months that way :shock: !
