hello there and I need help the boat is a 23 wellcraft with a mercruiser 228/305 alpha gen II, the carburetor is a rochester quadrojet been rebuild recently by a shop, how can I test if the carburetor secondaries are opening? thanks.
Put it in the water.Start it and take off the breather.Then go!!! Let someone else drive as you watch it as you accelerate.Somewhere after 3400(I think)they should open.J
ok thanks I will check that way I really dont think they opening I can't go over 3100rpm, the engine been service not too long ago, new cap, rotor, plugs, ign wires, fuel/water separator, the timing is correct, someone recommend to change the prop I was using a four blade 14 inch diameter 21 pitch, went down to 14 19 pitch and not changes at all so at this point I need to inspect the carb, thanks
Q-Jet has mechanical secondaries. Take the flame arrestor off and just push throttle full forward and look down the barrel of the carbs with a flashlight. No need to have the thing running.
Q-Jet has mechanical secondaries. Take the flame arrestor off and just push throttle full forward and look down the barrel of the carbs with a flashlight. No need to have the thing running.
No it has to be running they are pulled open by the vacuum and only open under load. Mine open as soon as I floor it while in gear. If you are slowing accelerating they will open depending on spring tension somewhere between 3000 and 3400 RPM. If I go from idle in gear to full throttle they open almost instantly.
Push them down manually by hand to make sure they do not bind they should open to about 75?
If there vacuum operated you either have bad vacuum diaphragm, a leaky or missing vacuum hose, or the linkage fell off.
If there mechanically openned your linkage probaby fell apart.
Look closely at the shafts and rods that push and pull stuff on your carb, make sure everybody is connected.
You can check a vacuum diaphragm by pulling the vacuum hose of the diaphragm, put on a nother piece of vacuum hose about a foot long or longer, long enough to get your mouth to it. Suck on the vacuum hose, something should move if the diaphragm is good. If nothing moves and you can keep sucking air the diaphragm is probably shot.
On the secondaries if the top plate is not opening you are not getting any gas as the plates operate the fuel rods. What I do especially on boats is reduce the tension plate spring by about 1/2 in order to allow the top plate to open easier. Its a locking bolt under your vac rod on the secondarys and there is a screw on the side. I did one for a friend when I rebuilt his carb, he said the boat was much more responsive and he gained 3mph. Buz
Sometimes after a mild backfire through the Quadrajet, the upper secondary air valve butterflies jump over the stop tab at the rear of the carb body preventing them from opening even though the lower secondary linkage opens the lower secondary butterflies. You should be able to push the rear of the air valve down with your finger and feel mild spring tension on the air valve butterflies. If not you need to apply a little more force to push the butterflies down back into place. The tabs are sometimes broken off or feathered causing this problem to re occur. You can, carefully loosen the air valve butterfly screws (No more than 1/4 turn as the bottoms are peened over and may break) and back up the butterflies a little more under the stop tabs. Note*** You cannot open the air valves with the engine idling because the choke pull off / secondary dash pot controls the rate at which the butterflies open in combination with the return / tension spring.
