Replacement Exhaust Bellows - Bellows vs. 'Tube'?

obsessive

New Member
Jun 11, 2007
151
Hampton, IL
Boat Info
99' 240DA
Engines
5.7L TBI - 260HP
Hello, all.

My 99' 240DA is in need of an exhaust bellows (the shift cable bellows was done a year ago along with the shaft bellows - not sure why they didn't do the exhaust as well (I'm unsure how long it's been torn).

While researching, I see that they offer both a standard bellows and a 'tube' style that only attaches to the transom end and mostly seals at full drive down position (the standard and tube style are the first two items in the linke below)

http://www.mercstuff.com/exhaustbellows.htm

What gives? Mercruiser offers the the tube as a standard part number. What are the advantages/disadvantages? I can do the tube while in the yard without removing the drive - I can't obviously do that with the bellows. Heck, the bellows tool alone is more than the tube.

Input appreciated.

Eric
 
My 330 had the tubes on BIII's. The poop was supposedly that they allowed the larger motors, or the motors that sat further forward with jack shafts (and longer exhaust) to breathe a little easier, as some of the pressure escapes before going through the drive.
The big advantage is the ease of replacement as you noted. They do create a little more noise vs the bellows, although I never felt my 330 was "loud", and there were two of them!
However, I always felt that my 330 pulled a little more exhaust fumes up and over the transom (station wagon effect) than other similar boats, and wondered if the tubes contributed to that??
Take care
 
Our 496 has the tube as well. The station wagon effect does exist, but on our boat the swim platform is over the entire drive, so whether the exhaust exits at the transom, or it exits at the props, at low speeds it will collect under the the platform. Keep in mind you really should not be running the engine with a Bravo in any position but down (I have the repair bills for BIII drive shafts,bearings, u-joints, gimbal bearings etc to prove it) because the Bravo drive shaft spins when the engine is running. Thus every time you raise, or lower the drive with the engine going it loads the u joint and gimbal bearing.

Henry
 
The exhaust bellows is basically an insignificant piece. If you want, you can just keep running your boat the way it is. If you do decide to change, definitely use the tube/cup design. Noise is supposedly an issue, but like mentioned above, I also have never noticed a difference.
 
Thanks, guys. That's what I thought. The boat could have been like this for some time last season - who knows.

I figured that the only thing that the bellows accomplished was to ensure that under light cruising it would cut down on the noise a little bit, even that, why would they even bother? I just want to make sure that it won't harm the engine (water backflow, etc.)

I don't really care about the station wagon effect - if indeed it's been broken for awhile, it's basically been acting like the 'cheater' pipe - and I havent noticed any exhaust smell, etc.

Does the fact that I have an Alpha GENII have anything to do with this? I would think not, since it's the same part number if I'm not mistaken.
 
Nope - doesn't matter.

Great, thanks!

FYi - I also spoke with the owner of the boat yard and he said that the only side effect is that it may be slightly louder, but nothing significant. Since it's likely been that way since last season, I seem to remember a little more exhaust noise than usual (we had it stored for a complete sesion prior to that, so I kind of forgot how it normally sounded cruising).

I'm going to get one of the cheater pipes and be done with it.

Now, it's off to fixing the fiberglass where the previous boat yard cought a chain or something on it when pulling it out with their crane.
 

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