more Rochester Issues NEW PROBLEM POST #10
 

Motor runs great 5.7 only problem is starting is hard and when the motor is shut off i get fuel from what seems like all the gaskets on the carb leaking fuel all over the intake manifold i just changed all the gaskets but this did nothing...any ideas?

my holly carb was leaking out of the bowels just tightened up with screw driver no more leaks

The qjets float bowl fuel level is below the gasket on the carb. If it's not leaking from a crack, it's probably a bad float valve causing fuel to spill out the vent.

I had it appart and filled the bowl no leaks. Also changed the seat and needle attached to the float. Where is this vent it would leak from

The vent is the 3/16 tube sticking out the top with an angle cut on it.
Could it be your float sunk? Maybe replace that too. Also guessing you set the float level correctly.

Throw it away and buy a Holley.

ok here is what i did i semi took it apart while on the motor...i disconnected the coil so i could turn over the motor without spark. The float seems to work ok...how to i adjust it to close the needle a little tighter becuase here is what its doing.

If i crank the motor over it seems to hold back the fuel when the bowl is full but than if i wait about 30 seconds it seems to have built up pressure in the line. it slowly starts to fill up the bowl and than overflow it. any tips on how to fix this?

Do you have hard fuel line between the pump and the carb?
The float is set so that the fuel is at a certain level in the carb for correct metering. You set it as by bending the arm metal connected. Do not bend it to close the neddle/seat tighter.

anybody have any idea what this backed up pressure is? is it normal the fuel pump is new and the right model for the boat.

New Issues
 

ok i seem to have the leaking issue resolved. It did turn out to be the seat and needle at the float.

New Issue: The motor will not rev above 4000rpms It doesn't pop or hesitates just bogs its weird it bogs down above 4000 and runs great up to that point. It also seems to heat up a bit once im there to about 185 motor normally runs at 160 something is going on.

any ideas? Im so fed up with these carb issues I want a new one!

You can always press the accelerator pump rod at anytime and you will feel if the carb is out of fuel, it will go down very easy. Normal it is pushing the fuel so it is harder to press. Sounds like it is running out of fuel at speed.

that was my first thought but how do i check that at 4000 rpms when i slow back down the fuel is there.

Do it at 4000, get someone to hold the wheel for you. Only takes a second.

whats the easiest way to check fuel pressure on these older boats with mechanical fuel pumps... I have changed all the fuel lines and changed all the fuel filters...can anyone recomend a cheap tester?

Your secondary air valve is opening too soon. You need to set the spring pressure per specs. When the secondary valve opens too soon you get a bog and a lean condition which causes heat.

i want to adjust this secondary valve spring....where is this adjustment i know is an allen key but i dont know where it is. can you give me some advice on adjusting this properly

thanks guys
Harry

Its been a long time since I rebuilt a qjet, but the screw is right under the left hand side of the secondary throttle valve shaft. If you had the carb off and upside down you'd be looking at it. It adjusts the amount of spring tension in the valve and controls how it opens. I don't have the spec on how far you turn the allen bolt after light tension is felt. Its something like 1/2 turn.

The allen screw is the lock for the actual tension adjusting screw. There's a small screw in the side of the air horn, parallel with the end of the air valve shaft. This is what adjusts the spring tension on the air valve. You must partially open the air valve to access it. Use a mini flat blade screwdriver to hold it in place (it will have tension on it) while loosening the allen screw. Increase the tension and tighten the allen screw to lock the adjustment screw. I usually increase tension 1/4 of a turn at a time until there is no bog under a hard acceleration.

i made the adjustment half a turn nothing...this is odd becuase last week the boat was fine...i have changed all filters here is what its doing

Jumps on on plane quicky then cruises great, runs well to 4000 then when i try to push it more it just dies no popping just nothing if i throttle back it jumps right back up....my father thinks it will be a timing issue. I haven't rececked that yet but it was fine begining of the season. The distributer is tight cant even budge it. what would cause it to run hot?

I fought this problem for the past few weeks and was about to tear apart my carb but replaced the fuel pump instead. Problem solved. Also check the valve at the tanke to make sure it is not gummed up restricting the fuel flow at high rpm.

You can test your fuel pump with a vacum guage. it will tell you all kinds of things about what is going on. Find an old school tune up kit.

Good luck
Ryan

Fuel Pump is 2 weeks old...if i unplug the line from the carb and disconnect the distributor and turn the motor over i get fuel shooting 15 feet lol i think the pump is in good working condition...i will check the valve again but cleaned it to start the season.

Hey,
Sounds like the top butterfly is not opening. Was the boat running ok then just nosed over about the time the secondaries should kick in?

looking at the front of the carb there is a rod on the top left side that connects to the choke pull off diaphragm. Make sure that linkage operates freely, and is not bent.

hope its simple.

idk i tried driving and looking and i looked back when i hit the gas it opened about a quarter but also bogged down i don't know if the engines rpm opens it up and that fact that its bogging is the reason it doesn't have the pull to open further. ill keep searching for my answer thanks guys

OK, directly underneath the vent tube on the float bowl is the power piston. When you open the throttle and engine vacum decreases, a small coil spring lifts the power piston and front metering rods. With the motor off, you need to insert a small pocket screwdriver sized object down into the tube and let it rest on the top of the piston. Then very gently, see if you can push down about 1/4" and then have the piston lift spring push the screw driver back up.
The piston should move up and down very freely. If its stuck, and I have seen it hundreds of times, you will go lean as heck on the front two barrels and never make any power.

As for the secondary air valve, air flow being drawn into the motor thru the secondary ( rear ) throttle plates pulls the air valve plate open against a very weak spring pressure. As the air valve shaft rotates open, it operates an internal cam which lifts the secondary meetering rod holder and thusly, the metering rods out of the secondary main jets allowing more fuel at full power. If the motor is not drawing in the air, the plate will not open fully.

The secondary throttle shaft lock out cam is behind the choke mechanism. It is there to stop the secondaries from opening on a fully cold engine. Make sure it is not seized part way off and stopping the secondaries from opening.