CenturyUltra

31' scarab twin 502 Carb motors, motors have low hours, ran good previously with no changes to setup, one motor now won't turn over 3500 rpm under load but runs fine otherwise, will rev higher out of gear, seems almost like Carb secondaries aren't opening but they are, hard to tell what's happening because it's loud (dry exhaust) and other motor kind of compensates and it only does it on plane around 50 mph, has msd distributors with no boxes and locked timing, any ideas on where to start?

F-2 Speedy

iTrader: (6)

swap carb's

underpsi68

Check fuel pressure and than compression and leak down test.

CenturyUltra

Thanks for replies, it runs fine getting up on plane where it's under load but rpms are lower which makes me think no internal damage to motor

TxHawk

iTrader: (2)

Ran good previously. How long ago was previously and how was it stored?

CenturyUltra

Previously was earlier this summer

SecondWind

I wouldn't rule out an ignition issue.

ezstriper

ck timing make sure it has not slipped

CenturyUltra

i did verify distributor was not loose but I will check with light

dereknkathy

Sock on the bottom of pickup tube in the tank.