6hp johnson runs nice but very slow

[slate1234]

Hi I'M running a 3meter sib and 6hp johnson I have just got I took the boat out today and it run really nice, but it is very slow, I also have a 4.5hp mercury and it seems faster that the 6hp in the boat is me 160lb a 25lt fuel tank half full and two rods and tackel, I tryed moveing the tank forward ect but seems very slow any ideas
Thanks

 

[steelespike]

Re: 6hp johnson runs nice but very slow

Very possible it is running on one cylinder.Unhook one plug wire at a time and see if it will run.

 

[slate1234]

Re: 6hp johnson runs nice but very slow

I just pulled the plug leads one at a time it kept running but i got got one hell of a belt from the bottom cylinder

 

[steelespike]

Re: 6hp johnson runs nice but very slow

You may want to consider new wires.But it could just be an indication of stronger spark on that cylinder.
A compression check would give you a good idea of the overall condition of the motor.
100 psi is an ideal minimum and within 10% between cylinders.Motor will run on less but not ideal.
Be sure the link and sync is correct.Carb opening all the way?
You may need a carb rebuild with special attention to all passages and jets.