carb help

[sidewayzbimmer]

It is off of a 1979 omc 120hp 4cylinder motor. Same motor that came in a 1969 nova. Carb was just rebuilt to what the book says
Float level 1/2"
Float drop 1 3/4"
Pump rod adj 1 5/32"
Choke unloader adj 0.110"
Idle mixture 2 turns out.

It idles good, revs in neutral to 3k rpms, but in foward only to 2200rpm tops. When you slow down it pops and spits bad ?

Thank you
Any help appreciated

[Coops Brother]

this in a boat? OMC, or GMC? If in a boat it might have points, check them.

[sidewayzbimmer]

It is in a boat. Points are right on, new distributor, plugs, wires, cap, rotor, timing is right on. Starting popping a little the carb was rebuilt. Now after its rebuilt it is way worse.

[juicedimpss]

you sure the pump is keeping up?sounds like a possible pump getting weak.

[Prince Valiant]

I agree w/ ron...sounds like you're running out of fuel/going lean.

other things to check include: are you sure there is no vacuum leak? Got a good gasket b/w there intake/carb? The carb body/base isn't broken?

[sidewayzbimmer]

there is a new pump that came with carb rebuild, gaskets are good dont think its broken will have to look it all over again. Thanks much for the help so far.

[juicedimpss]

i would try tapping a fuel pressure guage inline to be sure it is delivering.
if it is making/holding fuel pressure,i would start looking at a compression test to be sure there isnt an intake valve hanging open

[03Mach1]

If you have access to an outboard style 6 gallon fuel tank with primer bulb, hook that up directly to the fuel pump nipple, bypassing the boat fuel tank and anti-syphon valve. Sometimes the anti-syphon valve goes bad causing a fuel restriction, most noticable under load. This also eliminates any bad gas in the tank or a restriction in the fuel pick-up tube. But on something that age, I would start with a compression and leak down test so you don't throw parts at a soft engine.