98 yamaha 2 stroke loosing power

[PNWDUDE]

Hello fellow boatsmen!

New the forum here-
Ive been working on a 98 Yamaha 115hp 2 stroke. The motor looses power at around 4200 rpm. I squeeze the ball a few times she powers back up! After a carb rebuild kit it idles and runs great at about 20-25 knots and to get this out of the way- no I have not tried an external gas tank yet. That being said,
I’ve replace the plugs fuel pump, filter, fuel line and squeeze ball and rectifier. Still no luck!
I’ve done a compression test- OK
checked timing-Ok
Looking for any and all ides!
Thanks!

 

[racerone]

Fuel pump is driven by pressure of crankcase compression.----Checked that ?

 

[PNWDUDE]

Fuel pump is driven by pressure of crankcase compression.----Checked that ?

I did a compression test. Is there another way to check it?

 

[PNWDUDE]

Hello fellow boatsmen!

New the forum here-
Ive been working on a 98 Yamaha 115hp 2 stroke. The motor looses power at around 4200 rpm. I squeeze the ball a few times she powers back up! After a carb rebuild kit it idles and runs great at about 20-25 knots and to get this out of the way- no I have not tried an external gas tank yet. That being said,
I’ve replace the plugs fuel pump, filter, fuel line and squeeze ball and rectifier. Still no luck!
I’ve done a compression test- OK
checked timing-Ok
Looking for any and all ides!
Thanks!

Update- ran the external tank yesterday and found the same symptoms.

 

[racerone]

Fuel pump runs off crankcase compression pressure.----That is NOT the same as cylinder compression.

 

[PNWDUDE]

Fuel pump runs off crankcase compression pressure.----That is NOT the same as cylinder compression.

For what I have researched there is no way of testing the crankcase so that gets me nowhere