'70's Weekender/SRV300 exhaust boxes

[Captain Crispy]

I have read a few posts here and other sites about the exhaust boxes for the '70's 30 footers with inboards. These are the fiberglass boxes built into the hull at each corner of the rear bilge where the side exhaust exits the hull.

Are these chronic problems ? How would one know they are bad or about to go bad ? What is the most cost-effective fix ?
How difficult is it to put in a standard inline muffler and a thru-transom exhaust ?

 

[AnchorsAweigh]

I have those muffler boxes and personnaly really like how they work. They're so quiet until a little wave goes by and lifts them just above the surface and then "vrum rum rumble", nicer sound than any Harley could ever make! I don't know any history about them but mine leak a little bit, but usually only when idling or slow putt. When I throttle up a bit the pressure and/or vacuum created must help them flow without leaking. I too am interested in how to seal them up properly. I've reached up inside the exhaust holes and spread some sealant around where the copper pipe comes through the hull, but I'm sure it it leaks in other places too.

 

[Captain Crispy]

So the exhaust exits the hull under water [most of the time] ?
The leak you are talking about, is that a leak around where the bronze fitting goes through the hull ? How do you know it is leaking, rather than just having water coming through the exhaust hole ?

 

[AnchorsAweigh]

Yes, the exhaust holes are under the hull and only when you're light on fuel and/or a cross wave lifts the stern up a bit does it come out there. There are also little pressure port holes on the transom where it can release vs. bubbling up and out the side or aft. The leaks I have are hidden behind the massive fuel tanks on both sides so I can't really tell for certain where it's leaking. I just know that they only leak when running and it seeps out from under the fuel tank for nearly the same length as where the boxes are located. The water is not enough for me to be concerned about but I would like eliminate any actual exhaust that could be getting in the engine room.