1999 50 HP 4 stroke problem

[yakmaster]

I have a 50hp 4 stroke 1999 model with a problem I would like some advice for please.
Running at WOT sudden loss of power to a stop, could not restart for some time then ok at around 8 knots when trying to increase speed serious missing and wouldnt run at high speed.
Major service carried out last year and running ok since
Checked fuel system and replaced filters flushed system drained carbs - all ok
Checked cooling system found thermostat not opening and replaced same. test run boat - same result as above.
Removed leg, back flushed system and checked water pump all intact in good condition.

[Sparkieboat]

sounds like a fuel issue..you can get a fuel pressure gauge (e-bay) and test if it is an EFI..if it is carb, you have a clogged carb or bad fuel pump or fuel line sucking air somewhere.