engines won't rev past 3000 rpms under load

[chasmans]

/Twin inboard chevys 305 228 hp . Both engines wont rev past 3000 rpms. They bog down and won't reach plane. No bottom growth fuel is fresh engines in tune , carbs rebuilt correctly. new filters plugs wires. Any suggestions ?

 

[sandkicker]

More information!!! Starting with, did these engines ever run to specified WOT RPM for you?

And...if engine isn't running correctly how do you know "carbs rebuilt correctly" ( just sayin' ).

More food for thought.
Plugs...gapped properly? ( most plugs need user to gap them to specs)
Correct wiring distributor to plugs???
Which ignition system?? Points or Thunderbolt, IFSO which T'bolt????

 

[makomark]

ignition timing working properly?

Fuel filters clean? Anti-syphon valves checked?

 

[chasmans]

They have points . fuel filters replaced. When I first got boat It reved to 4600 and got on plane very easily . Antisyphon valves replaced.

 

[chasmans]

just an update , with compression test I found two dead cylinders.

 

[fastjeff]

Ugh! That will do it.

Are they side by side? If so, you might have a blown head gasket.

Jeff

 

[chasmans]

Ugh! That will do it.

Are they side by side? If so, you might have a blown head gasket.

Jeff

They were side by side with zero compression

 

[kghost]

Blown head gasket...

 

[mcomm]

Easy fix.

 

[fastjeff]

Make sure the head and block in that area are not gouged out by exhaust blasting back and forth. If so, she'll blow another head gasket right away.

Jeff