I completed fabrication of a new waste holding tank using the “stitch and glue” technique. I used tank design that Nate Houser, also a 350 owner, came up with when the tank on his boat failed. The old tank shape could not be replicated due to its placement within the boat under the cabin sole at the time it was being built. Nate came up with a new design that fits in part of the old tank location but with a modified shape (not the same space). The amazing thing about this design is that it comes in at the original tank volume of 30 gallons! Link to Photos of IP-350 Waste Tank replacements.
Original tank shape
First I had to carefully cut out the floor so that I could get the old tank out. I had to cut the top of the tank out then cut it into 2 pieces so that I could get it out of the new opening. Tank was very holey!
The new tank slid right into place and I held it down with some oak cleats. Once the tank was in and the opening trimmed with teak strips the new hatch was set into place.
I used a Dremel Multi-Max to carefully cut the opening into the floor. The cleaner the opening is made the better the final fit of the floor board will be.