Merc 4.2l D-Tronik, Exhaust tube or bellow???

[Noldisx]

Hi folk
I have a Doral 31 with 2 Merc 4.2. D-Tronic. Max speed 36 knots
I ordered a kit with bellows and seals.
There are 2 different kind of exhaust tube/bellow in the kit.
I think to reduce noise as much as possible the bellow would be better.
BUT....
Bravo Models Exhaust Preparation
IMPORTANT: When installing through the transom exhaust, it is recommended that the
exhaust bellows on the transom assembly be removed. This is necessary to avoid creating
a vacuum at the exhaust outlet in the propeller at higher boat speeds. This vacuum could
degrade propeller performance on some boats.

• If required, remove and discard clamps and bellows from gimbal housing.
• IMPORTANT: When installing through the propeller exhaust:
• • With Bravo One and Bravo Two Sterndrives, an exhaust tube MAY BE INSTALLED for
• a slight increase in performance.
• • With most Bravo Three Sterndrive Models, an exhaust tube MAY BE INSTALLED for
• a slight increase in performance.
• • With a Silent Choice Exhaust System, the exhaust bellows must be removed and an
• exhaust tube MUST BE INSTALLED.
• With any application, installation of an exhaust tube will increase exhaust noise.

Does anyone have experience with it?
Thanks, Noldi

 

[Fun Times]

Does your boat run through the transom exhaust which means the exhaust has cutouts with exhaust tips on the rear of the boat? ...Or do you have a Y pipe that connects to the transom housing assembly down low behind the engine?

Either way the removal of the bellows on Bravo stern drives was more meant to be for the high performance style boats that tend to run 60+ MPH so you'll be fine with either option you go.

My personal boat runs 70 MPH with a bravo drive and with through transom exhaust only installed, I have yet to remove the exhaust bellows as I haven't experienced any issues with it still in place mostly due to being lazy....Err' I mean haven't felt the need to remove it.

 

[Noldisx]

Does your boat run through the transom exhaust which means the exhaust has cutouts with exhaust tips on the rear of the boat? ...Or do you have a Y pipe that connects to the transom housing assembly down low behind the engine?

Either way the removal of the bellows on Bravo stern drives was more meant to be for the high performance style boats that tend to run 60+ MPH so you'll be fine with either option you go.

My personal boat runs 70 MPH with a bravo drive and with through transom exhaust only installed, I have yet to remove the exhaust bellows as I haven't experienced any issues with it still in place mostly due to being lazy....Err' I mean haven't felt the need to remove it.

I Have a single pipe down that connects to the transom housing assembly.
On the outside there is the option between gas out through a short rubber tube or mounting a bellow which guides the gas into the outdrive and let it out under water. I want the boat as silent as possible. Just bought the boat and there was just the tube installed. But for noise reduction I think I will install the bellow. The disadvantage is just above 60MPH. (gas through props)