200hp losing power over 3500 rpm

[zack_13]

I have 1991 twin 200's. They run fine at low speed, but at 3500+ rpm
they will stall. Both stall, not at the same time. It would take 5 to 10 minutes
before one would stall. Changed gas (fresh), fuel lines, cleaned tank,
cleaned carbs.
Now they run for about 30 to 40 minutes and then one will stall.
Can't figure it out.


Thanks

[boats.net]

Might check fuel pickup tubes in gas tank and antisiphon valve at pickup.

[zack_13]

Thanks
I changed the pickup tubes. Originals used to be metal, new ones are plastic.
The valves connected to these tubes are not anti-siphon,
do they need to be?

[Hamfisted]

Check primer ball...

Do you notice when this stalling occurs if the fuel line primer ball is collapsing? If so, there's a blockage between the ball and tank pickup.
With the motor turned off, can you pump up the primer ball firm on each motor? If not then you probably have bad mechanical fuel pump(s) and need new ones. Only other time I've seen this problem is when the O-ring on the main jets is cracked or missing. But you said you just went through the carbs. Did you notice the orange O-ring on the main jets?



- Mike