CONTINUOUSWAVE

[On an unspecified boat] I am removing the reversible pilot seat and a 20-gallon MOELLER fuel tank. I am installing a 30-gallon oval shad [bait] tank, in place of the fuel tank.

Will the area [where the 20-gallon MOELLER fuel tank and the reversible pilot seat were located on the unspecified boat] support 200-gallons of water and 250-lbs of me[?]

What is the best way to mount [the new tank]?

Newportwhaler17 wrote:...I am installing a 30-gallon...tank...Will the area...support 200-gallons of water...[?]

Is the new tank a 30-gallon tank or a 200-gallon tank? You mention both capacities.

Or did you mean that the 30-gallon tank when filled with seawater will contain about 200-lbs of weight. That's not the right figure.

Seawater has a density of 8.68 lbs/gallon, so a 30-gallon tank at full would contain about 260-lbs of water weight.

Newportwhaler17 wrote:...Will the area ...support 200-gallons of water and 250-lbs of me[?]

In order to know if the deck of the unspecified boat you are asking about can support this weight, we would need to what was the loading in lbs/square-feet on the deck with the old fuel tank; to know this we must know the area of the old tank base that rested on the deck and the total weight of the old tank and its contents when at full capacity. We also need to know the area of the new tank that will rest on the deck; we already know the weight of the contents, but how much does the new tank weight when empty?

If the new tank has the same loading in lbs/square-feet as the old, then to assume the deck could support the new tank would be reasonable.

Also, you don't make clear if you plan to use the new tank as a seat. If that is so, then add your weight to the total weight when making the loading calculations.

When you calculate the loading, if the new tank loading is higher than the old tank, you could install a sheet of plywood around the new tank to spread the load over a larger area so as to reduce the loading in lbs/square-feet.

Newportwhaler17 wrote:What is the best way to mount [the new tank]?

Regarding how to fasten a new tank to the deck of the unspecified boat, we would have to know more about the boat. Perhaps you can mention the model or in some way identify what boat you are asking about. Mentioning the model and year of the boat would also give insight into how the deck was reinforced. All of this information could have use in answering your question.

A good way to assess if the deck structure can tolerate the loading of your 250-lbs body weight will be to go to the deck area and stand on the deck on one foot, raising your foot heel so the weight is concentrated on your foot pad near the toe. While doing this, have an observer measure any deflection in the deck cause by your weight. When you sit on the new tank as a seat, your weight will be spread over a larger area than during your test with standing on your tip-toes of one foot. On that basis you can reasonably assume the same weight spread over a larger area will not cause deflection in the deck.