Pismo10

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.

formula18

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

Pismo10

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

formula18

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?

blue thunder

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.

formula18

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

blue thunder

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.

cubicinches

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.

formula18

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?

misskristy

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