It's used regularly.
No marine growth.
Last week it was fine. Today its lost 1k revs.
The throttle is fully open in the engine, when the helm is fully pushed, no slippage.
Petrol is good, swapped to an external source to check.
Prop looks ok. Not sure if its slipping.
Engine sounds like its missing a cylinder, hence my checks tomorrow.
Any other ideas please shout ... I will check for them all again tomorrow, dont want to miss the P1 boats in Sunday, got to get it fixed!
Thanks for you suggestions