Idle Mixture screws

[AK_quad]

I just got a rebuild 17058504. I installed it on my 350 mercruiser and ran pretty well except when trying to adjust the mixture screws. The screws have no effect whatsoever.  Even turning them in all the way does nothing, engine runs the same. Timing has been checked and right on. Idle speed between 600-700. Could the needle screws be the wrong length? Any ideas would be appreciated. I'm waiting to hear back from the rebuilder and I don't really want to ship it back from Alaska. $$$$$
Thanks

[429bbf]

wecome aboard . have you tried them without the springs? pull them out and check the length comparied to each other.remove the springs and try again.if that doesnt help it may be jetted a little rich. hope this helps .dean

[AK_quad]

Ok on the springs Dean. I'll check that today. I am wondering if I am getting some drip from the primary nozzles? I'll look for that today also. The rebuilder ask me what the fuel pump pressure is at and I don't know without plumbing in a gauge, which is not very easy. The mercruiser shop manual says it puts out 4.5-5.0 psi. I doubt it is putting out too much since the Qjet taken off didn't have a issue with idling. I'll try and troubleshoot some more.

[Cliff Ruggles]

Rebuilt from where?.....Cliff

[AK_quad]

The custom rebuild was done by SMI in Huntington Beach, CA. I got it installed and working well. I could not get the base plate sealed on the manifold completely after trying at least five times. Used three different gasket types and then tried a 1/4 thick gasket and got it sealed. The seal I received would not seal and all attempts was done torquing down with a torque wrench. The 350 mercruiser engine is now pulling 18 inches vacuum at 650-700 rpm and mixture screws work as they should. Now I would like to rebuild the one I took off and have a good working spare. I'm looking at your kits Cliff. Can you recommend a kit for a 17080565? I'm looking for MPG and that's why I had SMI do the custom rebuild on another new carb. I didn't want to down the boat for this summer waiting for the turnaround time for a rebuild. The summers are short up here in Alaska.

[Cliff Ruggles]

If the intake is clean and flat, and the carb base clean and flat, and the correct gasket is used, it should seal up without torquing down any bolts, just snugging them up.

Torquing down the long front bolts will warp the airhorn, main body, and ruin the carburetor.

Can't really help out with a "custom" unit from another source.  I see PLENTY of these sent here, as at least 30 percent of our business is custom tuning nice new carbs that do NOT work.

There are a variety of reasons for this, most comes from using poor quality parts, and calibrations are WAY off where they should be for the intended application.

I would go back to the original unit, install one of our kits, and make the correct float setting.  I'll bet you a steak dinner it will work much better than the custom unit at every level.  If not, send it here and I'll let you know why it isn't.......Cliff