These are my experiences replacing the holding tank for a 1995 Hunter 37.5. For those of you considering the purchase of a used 37.5 and have come across this post, don’t let this issue scare you. The boat is wonderful (we're on our 9th season). The original aluminum holding tank, however, is subject to corrosion and will need replacement. BUYING THE TANK Due to a change of heart, I ended up purchasing two replacement holding tanks, only one of which was installed, so I have quite a bit of shopping experience. The first tank was a STOCK Ronco Plastics that was purchased in a rush last summer (2002) when my old tank got its first leak. As a temporary fix though, I was able to patch the old tank with Marine-Tex and that ended up getting me through the rest of the season. The second tank is a larger custom poly tank from C. C. Tech, built to match the dimensions of the original aluminum tank (purchased Feb 2003) and is the one I installed. BOTH SEEM TO BE VERY GOOD TANKS. I obtained the line drawing for the original tank from Hunter. The drawing is attached (I’ve scanned it as a .jpg file, if the resolution does not hold up for display on HOW, you may need to get a copy from Hunter). I believe it applies to other years of this model boat, but you should verify your own dimensions. This made ordering the replacement tank easy since I simply faxed the drawing to both Ronco and C. C. Tech and told them to follow it for fittings placement etc. I made one modification and that was to instruct them to weld the brackets flush with the bottom of the tank, rather than 1/4” below. RONCO PLASTICS TANK I ordered the largest stock tank from Ronco Plastics that would fit in the original space without surgery: model B227, a 20 gallon tank. (Ronco may add other appropriate sizes in the future, so please check with them ). Ronco customizes this stock tank to install couplings for inlet, outlet and vent hoses to pretty well match the original locations (including a stand-pipe to the bottom of the tank). In addition, they will weld “hold-down tabs” around the bottom of the tank so that you can easily fasten it to the floor and stringers, just like the aluminum brackets used on the old tank. Ronco also includes a 4” Beckson inspection plate on top. The price of the base stock tank was $105. Customized with all the above and the fittings brought the completed price to $178. This is a fantastic price. Ronco is great to work with, easy to talk to by phone, and the tank shipped in a week. I am impressed with the tank and it is as advertised (to quote Peggie Hall: “strong-walled-roto-molded poly” etc.) The B227 tank is a 20 gallon tank (approx). The original H37.5 tank is 25 gallons (approx). If you choose to go fully custom with Ronco (to match the original Hunter line drawings), the cost is $600 to build the mold and then the additional $180 to purchase the tank equipped as above. They don’t encourage it. Ronco Contact info: http://www.ronco-plastics.com Phone: 714-259-1385 ask for Rich C. C. TECH TANK This company custom-builds. The big differences with Ronco: tank panels are welded (rather than molded in one piece), the tank is made of 3/8” polypropylene (Ronco uses 3/8” polyethylene) and the tank is built to your exact dimensions. The price quoted me to replicate the tank for the H37.5 was $375, which included all the threaded pipe couplings, stand-pipe, Beckson plate and hold-down tabs. It took four weeks to build the tank, and at the time they told me 4-6 weeks. They are easy to work with over the phone. Overall, they built a great tank, but there was one problem I wanted to get corrected. I noticed that the finished tank had a stand-pipe with a sharp bevel at the bottom, and the highest part of the bevel was 2-7/8” above the floor of the tank (in other words, we were going to be sucking air at pump-out when the level got down to 2-3/4” above the floor). This was disappointing since I was losing some capacity—the one thing I was chasing by going to a custom tank. The problem was easily fixed after discussion with C. C. Tech, by gluing on an extension to the stand-pipe using a PVC connector with a squared-off end. BE SURE TO SPECIFY YOUR STAND-PIPE SPACE TO THE TANK FLOOR! C. C. Tech has now made note of that requirement on future tanks for Hunters. The stand-pipe in the RONCO tank was rigged to end 1/2” above the floor of the tank. Peggie recently recommended 1” or so in some other posts. Take your pick. I used 5/8”. The reason C. C. Tech uses polyPROPylene instead of polyethylene is that “it welds ten times better and is easier to fabricate with,” according to Bert, their tech manager. An FAQ including their view of poly vs. poly is on their Web site. Bert also provided comment on the HOW Web site on 4/18/03 in a piece entitled “Polypropylene vs. Polyethylene.” C. C. Tech contact info: http://www.gocctech.com/marine/boat-tank.htm Phone: 401-784-6168 Linda Kleinman for sales. Technical questions ask for Bert. TANK COMMENTS --Both tanks appear to be very well-built. Lesson learned on the stand-pipe issue is to spec *everything* to any manufacturer—don’t leave any dimension open to chance. --If capacity is not an essential concern, for example, if you regularly sail outside the 3-mile limit or have plenty of opportunity to legally discharge, then the smaller and cheaper stock Ronco tank is a great solution. If you have a capacity concern and don’t want to consider options like LectraSan or putting a larger stock tank elsewhere in the boat, then look to a larger custom tank to fit the original space. C. C. Tech, for one, custom-builds a quality poly tank at a reasonable price. --The original Hunter tank had a baffle, neither of the new tanks came with one. C. C. Tech will do one for additional cost. REMOVAL AND INSTALL The original aluminum tank comes out through the access panel in the aft state-room, but only if you saw off the existing aluminum hose connectors flush with the tank first (Sawz-all works great). I had to disconnect and move the manual bilge pump hose out of the way—this hose runs in-between the holding and fuel tanks. Tank fittings such as PVC elbows are screwed in to the couplings on the new tank after it is in place (these tanks are built with screw-couplings welded in place, that are almost flush with the tank walls). Obviously, I’m only speaking of experience on my boat—others may be different. Since you would prefer never to go back in to this area again but you have a grand opportunity while the area is wide open, rehose the entire system while installing the new tank, using Sealand OdorSafe 1-1/2” sanitation hose (per Peggie’s recommendations). The hose is tough to work with so to make it easier, use the custom hose adapters that Sealand makes specifically to go with this hose. The adapters let you use the hose with standard PVC fittings with socket connectors. Part #341513 from Sealand 1-800-321-9886 (ask for sales dept.) They may be available elsewhere, cheaper. Even using the proper Sealand hose adapters, OdorSafe hose is difficult to work with. I used all the tricks: dish-soap, West Marine hose lubricant, my brute strength, another person’s brute strength and in some spots, I gently used a heat-gun to allow the hose to go on a fitting. Rehosing the entire sanitation system was far more difficult and time consuming than the job of replacing the tank, which is what initiated the project. The tank was more or less an easy bolt-in replacement. I also replaced the head and all the sea-water supply hoses to it. This is one job that you might as well do completely so you are done with it for a few years. FINAL COMMENTS --As of this date (May 2003) my new tank is installed and leak-tested, and has been in “production” for one cruise of a few days. I cannot testify yet to the durability of the tank or other components. --Since the failure of aluminum holding tanks is inevitable, shop NOW for your replacement tank if you intend to keep your boat a while. --I take this opportunity to thank Peggie Hall, the “head mistress,” for sharing her wisdom. --I am not an MSD engineer; all of the above is just personal experience and opinion. Brian Leney 5/23/03