A 1990 is shown to have a temperature switch.----It is likely the overheat warning and needs to be investigated !----Sad that folks do not replace impeller every 5 years or so.
Check valve clearance.------Check compression ( throttle open ) ----The powerpack ( big $$$ ) has an optical sensor.-----Does spark jump a gap of 3/8" on both leads ?-----Perhaps oil pressure switch is acting up ?
The fuel does NOT go through the crankcase on these FICHT motors !!-----Crankshaft and bearings would not see any oil.------Motor would quickly come to a " dynamic halt " and be ruined.----
Roller at the back of the trailer half submerged.-----Pull boat on and it will center itself.-----When winch takes too much effort , back the trailer in about 4 or 5 ' more and repeat.-----Put my 30' boat on the trailer that way.-----Never an issue.