2hp problem

[Rowdyguy]

Hello all

I have a Yamaha 2hp model 2B, I did a service where I changed the sparkplug and it has not been the same ever since. (This may be due to starting the outboard while the leg was not in water as I did not know it had an imprellor at the time). It starts fine and idles fine but when It gets up to higher revs it starts to miss rev and eventually konks out. Not sure if it

A- Is over heating
B- Head gasket blown
C- Water is getting in to cylinder
D- Fuel problem

Have checked the imprellor and pulled apart and clearead out water passage.
What may be the soloution or problem hear?

Any help much appreiciated

[boats.net]

Check compression or removed the head to see if have head gasket or piston/cylinder damage.