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270 no top end rpm

T

toolguy1025

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"twin 270s in 34 bayliner. por

"twin 270s in 34 bayliner. port engine runs to 4400 per spec - starboard will only run up to 3200 then drops back and levels off at 3000 rpm. all ignition parts and filter new, linkage opens fully, all tune-up specs on the money. compression equal at 130lbs in all cylinders. any ideas???"
 
I'm going through the same

I'm going through the same problem with my port engine in a 33' Carver. My next troubleshooting is going to focus on vacuum. There is much less on port than stbd at full throttle so I may have a leak somewhere. No idea if this will help because I'm not even sure it's my problem.
 
"It isn't. If you had a v

"It isn't. If you had a vacuum leak that severe, the motor would idle horribly!

Need to go thhrough the usual list of suspects: Carb secondaries not opening fully, advance not advancing all the way, water in fuel, dirt in carb, a plug not firing (pull and inspect all plugs), cross firing ignition wires, etc.

Jeff"
 
"Jeff,

I've ran good ga

"Jeff,

I've ran good gas from a 5 gallon jerry can with same results, used carb cleaner, seafoam in gas to clean jets, straight into carb to clean intake and cylinders. Still can't get over 3000 under load. Secondaries opening and getting fuel. I will be checking plugs as well this weekend. I hate easter egging it!!"
 
all ignition parts were replac

all ignition parts were replaced in both engines at fitting out this season. after launch it would not turn up and had a terrible miss. was a bad #4 intake valve. head done and all cylinders have good compression now. have gone over all carb and dbr settings. only thing not checked was ignition advance. will do that next. if not that - how do i check secondaries? throttle plates do open - checked that and cables - but how do you check air valve on a q-jet? thanks!
 
checked advance - looked to be

checked advance - looked to be very sluggish and not going past about 10 deg add'l. don't have an advance light so it is an est. cleaned all mechanism and now marks move way over when engine rpm increased. at least twice as far as before. will take it out this week and see what happens!
 
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