50hp johnson 2stroke outboard.

[fishermanpaul]

Hi, I have a problem with my 50hp johnson outboard, I think it is a 1975 model. the problem is when its driving flat out she,ll do about 25 knots then all of a sudden she,ll drop speed to about 6 knots then pick up again then drop. i left it with a guy and he said he cleaned the carbs out and replaced the plugs but its still doing the same. also what is the correct plugs for my engine.
kind regards.

 

[Daviet]

Re: 50hp johnson 2stroke outboard.

You might try pumping the primer bulb while at WOT and see if it helps, if so you might have a defective fuel pump.
You can use a timing light to check and see if you are dropping a cylinder.
You could have a high speed orifice restricted and needs to be cleaned.

 

[fishermanpaul]

Re: 50hp johnson 2stroke outboard.

You might try pumping the primer bulb while at WOT and see if it helps, if so you might have a defective fuel pump.
You can use a timing light to check and see if you are dropping a cylinder.
You could have a high speed orifice restricted and needs to be cleaned.

hi i tried pumping the bulb and it seemed to help a bit then it went into limp mode.