Well, I had posted a thread on a leaky Rochester quadrajet on my 305 cu in. Mercruiser Alpha One. After about 20 rebuilds, new float, numerous tests. I decided it was an internal leakage issue, and it needed throttle bushings badly.
Therefore I purchased another "new" rebuilt Quadrajet from a respected source.
The unit was freshly redone from top to bottom. Overall the boat now runs flawlessly until the throttle is moved from a 30 mph cruise to full throttle. The engine will loose power immediately, and seems dead quiet. I can regain cruise speed once again, by simply pulling the throttle back. The engine comes back to life with no issue. Its very odd, like someone is flipping an switch. Sometimes I will get a backfire.
In any case I did some testing at the dock in neutral. The engine will accelerate past 3000 rpm, and the other two barrels will open, and the engine sounded very strong. I watched the vacuum piston draw the top baffles open, and all seemed ok.
What is happening here? Why can't I get that engine performance under actual operation?
Anxious to see the boat really go, with all 4 barrels working properly.
Is it fuel starvation? Float too low, vacuum leak, a linkage adjustment? Electric Fuel pump is putting out about 3 psi at idle, measured after the water/filter separator. I plan to change the filter, but would like to know where my acceleration disappears to during acceleration from a 30 mph cruise speed.
Update:
I have replaced the fuel line and siphon barb fitting. There was no problem at the strainer in the bottom of the tank either. Frankly the fuel delivery system seemed relatively fine, however it is now new. INterestingly, the carb guy I got the rebuild from, told me to bend up the tangs on the secondary metering rods holder. In other words this should bridge the starvation issue when secondaries kick in, or something along those lines. I will let you know if this is effective.
Thanks for your help!
Therefore I purchased another "new" rebuilt Quadrajet from a respected source.
The unit was freshly redone from top to bottom. Overall the boat now runs flawlessly until the throttle is moved from a 30 mph cruise to full throttle. The engine will loose power immediately, and seems dead quiet. I can regain cruise speed once again, by simply pulling the throttle back. The engine comes back to life with no issue. Its very odd, like someone is flipping an switch. Sometimes I will get a backfire.
In any case I did some testing at the dock in neutral. The engine will accelerate past 3000 rpm, and the other two barrels will open, and the engine sounded very strong. I watched the vacuum piston draw the top baffles open, and all seemed ok.
What is happening here? Why can't I get that engine performance under actual operation?
Anxious to see the boat really go, with all 4 barrels working properly.
Is it fuel starvation? Float too low, vacuum leak, a linkage adjustment? Electric Fuel pump is putting out about 3 psi at idle, measured after the water/filter separator. I plan to change the filter, but would like to know where my acceleration disappears to during acceleration from a 30 mph cruise speed.
Update:
I have replaced the fuel line and siphon barb fitting. There was no problem at the strainer in the bottom of the tank either. Frankly the fuel delivery system seemed relatively fine, however it is now new. INterestingly, the carb guy I got the rebuild from, told me to bend up the tangs on the secondary metering rods holder. In other words this should bridge the starvation issue when secondaries kick in, or something along those lines. I will let you know if this is effective.
Thanks for your help!
