Sorry, but...
No mfr provides parts for more than 10 years after discontinuing any equipment model. SeaLand (not Seaway) bought out the marine division of Mansfield in 1984...they discontinued the 751 shortly afterward, and the 752 only a year after that. No parts have been available for either one for more than 10 years. If it's any consolation, you may THINK that the only thing it needs is a cam and a flapper valve...but they're just the first parts to fail. Even if you could find 'em, other parts are so worn by now that any one of 'em are about to fail. Salt and other grit have also scored and scratched the inside of the pump cylinder so badly by now that even if you could rebuild it and find the parts you need, there's no way the toilet can move flush water and waste anywhere near as efficiently as it did when it was new. So putting ANY money into it is would be playing Russial Roulette...your toilet has finally worn out! Everything has a lifespan...If it's any consolation, it did last 3-5x longer than any toilet in its price range (<$150) that's made today. If you want another one that will last anywhere as long, spend about $200 for a Raritan PH II. A lot of people here have done so...you won't see a single post from any of 'em that's anything BUT the highest praise.
