Tired of the noise, the complaints, the applause when you shut it down? Well most of us still love the roar of open exhaust but the times are changing.
In response, Nor-Tech in conjunction with CMI has developed a new system for our Supercats that routes the exhaust below the waterline and through the transom below the gimbal housing.
This system virtually eliminates most of the noise at idle. To relieve any back pressure there are 1" vent pipes that exit above water but the maximum at idle with Mercury 850's was 83db. Well below existing limits. In fact most of the noise present is coming from the fuel pumps and blower whine.
Once on plane the exhaust is introduced into the prop flow.
At high speed the only sound heard both inside the boat and outside is again, the whine from the blowers. It actually sounds like a muffled turbine.
Mercury was concerned initially about possible back pressure. According to their tests not only was back pressure absent but it created a vaccum, flowing better than tail pipes.
The end results, close to totally quiet and no loss of performance or horsepower.
This system is available for all new Nor-Techs and available for the retro fitting of existing boats.
Terry

That sounds cool.

Hello Terry!
Sounds great, no pun intended.

Question: It would appear from your second pic that the exhaust exits directly in front of the prop. Are there any issues with planing and "prop bite" while underway?

Good question?????

No issues what so ever. Not enough going on to disturb the prop.

Did you try your boat with the exhaust on top first? Just to see.

We've run comparable power enough to know what to expect.
Acceleration,Top Speed and even fuel burn exceeded our expectations. As for the Slip factor - no change.
There really is no downside.
The folks at Mercury are very excited about this project and the boat will be on display at their dock during the Miami Boat Show.

Thanks for the answer.
Sounds like you guys developed a good solution to a problem.

Nortech Rocks! I love this solution.