Unfortunately were in a sensor age. Just had some problems with my outboard motor running in limp mode water issue, Changed the impellor 60 quid the thermostat the size of your finger nail was 80 I also ran some hyperchloride around the water channels which are raw water cooled to get rid of some crud. Ran her up exactly the same turns out it was a faulty heat water pressure sensor a snip at over 200quid plus the vat. If you were to bypass it everything works perfectly. If it was a car you pull over but out at sea going into limp mode throws up other issues and things can get very nasty quite quickly,,,,,Em
