1978 Johnson 150 wont go full throttle.

[10Rams]

Hello i bought a 1978 johnson 150 not long ago recently took it to the lake and whenever i give it full throttle it sounds like it just stays at half throttle. rpm's do not increase it will only go about 10 - 15 mph. i have cleaned the carbs aswell. fresh gas. not sure what else to check as this is my first boat. thanks!

[09emdog]

Things to check, what shape is your prop in? Is the nut on the prop loose? When you throttle up does it move all the way to full throttle? When your running it is the air release valve open on the gas tank?