Long ago I read somewhere that an engine failure very often occurred when changes were made to power settings, fuel tank changes etc. That was before I made my first water crossing, Mull of Kintyre to N.I. as it happens, and I have always attended to whatever needed to be fiddled with before coasting out with the intention of changing nothing until I was 'feet dry'. Don't know if it made any difference but it seemed sensible to me and I've never had to ditch.