I bought a mercruiser trs 400 without carburator, can anyone tell me how many CFM this carb must be?
tanks marco

The 400 came with a quadrajet carb I believe. It has the same internals as a 420HP 454, minus the GIL exhaust, and holley 800CFM 4150 carb. I would put a holley 800 on there, and upgrade the manifolds if they were not already. Good motors.

Thanks for the info " Mild Thunder"
I have to put a new starter on the engine because i uograde from trs to bravo.
are the trs 400 engines all right hand rotation?

Yes.

I dont think I would necessarily call it a "upgrade" from a durability standpoint. I believe the TRS is a stronger drive than a standard bravo. However, eliminating the trans, and going to a bravo, might give you a couple mph, and parts are more readily available.

thanks again, for the info

"fyi" all mercruiser engines get there rotation from looking at the rear of the engine forward.as such your engines are left hand rotation,or counter clockwise, and that effects how people accidently hook there sea pump hoses on backwords

You can run Bravo's ,,,,easy on those 400's or on any 420.

Unless you have a real heavy boat.

I have been told that a factory carb on a 400 was a 780 quadrajet. just my 2 cents

Cut the tab on secondary so upper plate opens more and change secondary metering rods and Q jet with give same top speed as 800 holley on your motor. The Holley will have more mid range punch, but no more top speed than Q Jet after secondarys have been modified. If you change intake the old 180 degree style with open plemun and a 1" spacer work real good on those motors. But than use a 800 or 850 Holley. Go to car swap meet and you can pick the old style intakes real cheap.