330 HP 454, Quadrajet. The carb was "professonally" rebuilt just before I got the boat. It runs well on the primaries but when I tip in the secondaries it stalls. If I pull the throttle back it will run on the primaries. If I go to WOT it sometimes will get up to top rpm but when I try going back to about 3200, just on to the secondaries it will stall again. Just checked timing, starting at a base of 10 deg. Perhaps too much spring tension on the secodary air valves?

Also is 210 degrees too hot when running flat out? That is exactally where the 454 in my truck runs with a 195 thermostat. The boat has a 180 . I cleaned the sea strainer but how should I check pressure from the sea water pump. There is a through hull scoop grate on the hull instead of picking up water from the outdrive like on my other bravo. The heat exchanger tubes looked clear and have new coolant. The boat was lift kept before I had it so it might not have been flushed much.

It sounds like the secondary air door is opening too fast or it is very lean. Take it back to your "expert" and tell him what's happening. Your temp is way too high. Stock those engines have 140 deg. thermostats and run very close to that at all rpm's.

Sounds like a lean condition. The Q-jet has secondary metering rods which go by a two letter ID code. They meter the amount of additional fuel fed to the engine when the secondaries open. Attached is a link to a chart. I would ask your professional rebuilder what he installed.

http://www.hioutput.com/tech/qjetrod.html

And, there are different hangers that the metering rods "hang" from. They hold the metering rods at different heights. A QJ is actually a very tuneable carb but it is completely different than tuning a Holley. Yep, I would definitely bring it back to the expert.

There is a small cam on the secondary buterfly plate in the middle that lifts the secondary metering rods. I had one of these break once. The throttle plates and buterflies would open but the rods would not lift so very lean codition. Only saw it once but it might be something to look at. Just open the secondary buterfly by hand and see if the metering rods lift up.

Jerry.

First, change out the water seperator in the fuel system. Had the same thing happen to me, engine would die when the secondarys opened. Had always been ok before that, so I tried the simple stuff 1st, turned out to be water in the gas. If that doesn't do it, take it back to the 'expert'.

Good advice. Always check the simple things first.