1963 40hp Johnson seahorse motor, need HELP!!!!!!!!

[the_one]

I have a 1963 40hp Johnson seahorse motor and I really appreciated all of your helps. I couldn’t get the engine to goes above 6 miles/hrs in full throttle. When it’s in full throttle engine reps up and look likes it started to speed up but less then 10 secs rpm dropped boat flatten out, this repeated constantly at full throttle. However, if throttle to lower speed the reping stop. I have replaced water pump, gas lines, new sparks plugs, gas filter, new throttle cable, rebuilt carbureted (all valves needle are still in good condition) and reset it back to original factory setting. Don't know what to do now.

Please Help.

Thank you.

[tashasdaddy]

havve you check spark can compression on both cylinders? have you tried pumping the bulb on the fuel line as you take off?

[the_one]

Yes I did both Tashasdaddy.

cylinder one at 91 psi.
cylinder two at 100 psi.

[tashasdaddy]

what about pumping the bulb. it sounds like fuel starvation on the timing and carbs are out of sinc.

[the_one]

what about pumping the bulb. it sounds like fuel starvation on the timing and carbs are out of sinc.

I done it all and the result are the same. One stupid question from me, if it's a fuel starvation why won't it affect at a low speed. Also I have left out one thing, if the throttle shift down to low of a speed engine wanted to stall. Maybe I need to replace the new bulb and fuel line that connected to the bulb.