20rl73 johnson 20hp 2 stroke outboard

[David wright]

Hey everyone first post here.
We have a 20 hp 1973 long shaft outboard, currently on our weston 670 22 ft give or take,
Currently on a calm river the maximum speed we can get at high revs is approx 7-8mph, and it seems very unresponsive when throttling forward, however in reverse it goes nuts, also cuts out after a run when idling on occasions and then wont start again until many cranks of the engine, we have replaced the fuel pump, new carb kit, im lost as to what the issue can be many thanks on any help here guys and gals

 

[racerone]

Sounds like it might be running on 1 cylinder.------In reverse there is exhaust in the water and less load on the prop.-----Post compression values and check spark.

 

[David wright]

Sounds like it might be running on 1 cylinder.------In reverse there is exhaust in the water and less load on the prop.-----Post compression values and check spark.

80 psi on both cylinders spark checked with spark plug tester

 

[David wright]

80 psi on both cylinders spark checked with spark plug tester

Also new spark plugs installed and checked fuel is getting to both plugs

 

[David wright]

Also new spark plugs installed and checked fuel is getting to both plugs

Also using premium unleaded fuel with 50-1 mix on castrol outboard 2t oil

 

[David wright]

Sounds like it might be running on 1 cylinder.------In reverse there is exhaust in the water and less load on the prop.-----Post compression values and check spark.

Thanks for replying racer you are somewhat a legend around here

 

[racerone]

Remove bypass covers to look at pistons/rings.---The 80 PSI compression is low.

 

[David wright]

Remove bypass covers to look at pistons/rings.---The 80 PSI compression is low.

Will this cause the intermittent engine starts ?

 

[David wright]

Remove bypass covers to look at pistons/rings.---The 80 PSI compression is low.

Also there is a kill switch linked to the plugs done by a previous owner and sometimes when turned to make to break it does not kill the engine it just drops on revs on idle

 

[racerone]

I can not see , feel your motor.----You have to do the testing and inspection.----Guessing and assuming do not work.----This should be a simple fix.---Sorry if my suggestions based on 50+ years experience did not please you.

 

[David wright]

I can not see , feel your motor.----You have to do the testing and inspection.----Guessing and assuming do not work.----This should be a simple fix.---Sorry if my suggestions based on 50+ years experience did not please you.

Of course they do i appreciate your help and will check all of your suggestions thank you