I too have a lawnboy with a small crack in the tank and I have tried JB Weld and it held for a couple of months and is now seeping ever so slightly. I have thought about getting a plastic welding kit, but discovered an epoxy made especially for plastic. I haven't tried it yet, but when the mowing season is over I will try it. It is called 'Fastweld' and is carried by Carquest, (auto parts store).

Briggs had a replacement program a few years back, but only if you took your mower to a dealer. In my case the dealer was going to charge $62 labor to replace the tank after they received a replacement tank from Briggs. I opted out and got a tank from a mower bone yard. I don't think Briggs ever fessed up to there being a problem with the tank.

Why is he trying to clean from the inside? Over time dust, contaminates in the gas, Grass, ect.. get into the tank. Gas jells this stuff, it sticks to the bottom, sides, and around the any exits. Then it harden or just floats around the bottom that don't get stuck. I find or IMO the every 3 to 5 years depending on the conditions the gas tank gets pretty cruddy. When I do Fuel system clean up I start at the Tank and work my way to the carb. I know some people just change the inline filter thinking that's all that needed. IMO it's not. Cleaned many plastic gas tanks with carb. this includes weedeaters, chainsaws, lawnmowers, Lawn tractors. My my 23 year old craftsman LT4000 plastic gas tank has been cleaned at least 10 times. I usually spray the carb. cleaner in, use bottle brush for the corners and dirty spots on the bottom. Then I blast it out with my pressure washer. Rinse, flush with gas, and let dry. This I inspect, blow out all the vent holes (including the cap, Course I cleaned it also). IMO you can use several chemicals including gas as long as you use the bottle brush, rinse and alow to dry out. I just found that carb. cleaner is more active initial before it evaporates. If carb. (in spray can hurts plastic then all the Zamma carb. would be melted POS cause I spray the shyt out of them to get them clean when they have been setting for year or more.

I don't have three acres but a 3 year old home on 3/4 acres. I have an older JD-LT155 with a 38" mower deck. It has no problems with the slopes, in fact it surprised me when it was able to climb out of the ditch in the front yard. While there are many solutions to the mowing problem, there are other uses for a tractor. I would recommend a tractor either one like the LT-155, or one of the heavier ones. With three acres and your desire to make additional planting, you will appreciated the tractor with a trailer to move all of the tools, plants, seeds, mulch, fertilizer, and things yet to be discovered that those flower beds and new trees will need. Right now I am looking at putting a water tank in the trailer to water those new remote plantings. If you can afford two I would get a tractor and the zero turn.