Good Problem

[Jimmy]

Finally got KTS wet this weekend. The A-4 roared to life quickly. Spring commissioning included bottom paint and a new cutlas bearing. She purrs along both quick and quiet....but too fast? At 29ft and only 7500 lbs , I think I'm at the smaller end of the A-4 scale. I find myself having to shift into neutral frequently as I navigate within the marina. At the current idle setting I'm steaming around too fast for several of the sharp turns and tight corners , not to mention its a pretty busy area with many others darting in and around.
I wanted to tackle this last year, but before I could I was hood- winked by an intermintant stalling issue . I needed to solve that so I could be certain that when I started mucking about with a carb for the very first time, I could clearly determine the effects of my actions.......finally here's the question....Do I simply adjust the idle setting, or play with the fuel mixture also?
Thanks
Jimmy

[Sony2000]

Start by unscrewing the idle setting completely, while running in neutral. It should run. Then while attched to the dock, put it in gear. Did it die? If so, 1/2 clockwise, each sucessive retry, until it doesn't stall. Other adjustments are, and will be, minor.

[Mo]

Don't laugh, it's been done and every marina has one

[YOUTUBE]8alNxLjCBJc[/YOUTUBE]

[hanleyclifford]

Mo - Wish they all ended that way!

[Jimmy]

yea...not quite that fast , but it does frequently end with the "Margarita"
Thanks

[msmith10]

Before you adjust the idle setting make sure the throttle stop is not the culprit. It's a quick check and easy adjustment. When I bought my boat it was set so high I couldn't idle below about 1300.

[roadnsky]

The following problems within the idle system (listed somewhat in decreasing order of likelihood) can cause uneven or unreliable idling:

IMPROPER IDLE SET SCREW ADJUSTMENT: Your idle RPM may be set – not by the idle set screw – but by the throttle cable itself. In other words, the idle set screw is backed off so far that the lower limit of the throttle cable is reached before the idle set screw. The problem with this scenario is that throttle cables do not have an accurate end point, and they don’t always stay where you put them. If you pull the throttle cable to its minimum position and walk away, it’s likely to spring back up or down a bit, moving the throttle control arm with it.

To check the idle stop, place the throttle lever in the cockpit at idle, then go down to the carburetor (with a flashlight and mirror if necessary) and note whether or not the end of the idle set screw is actually touching the idle stop coming out from the housing of the carburetor. If it is not, reposition your throttle cable so that the idle set screw does touch the stop.

This adjustment will probably result in too slow an idle, and the next time you start the engine, it will probably shut down as you slowly move the throttle to idle. So the next (and final step) is to readjust the idle set screw to the idle RPM that you want. In this new setting, the idle RPM will actually be set by the idle stop and not by the random positioning of the end of the cable.

CARBURETOR ISSUES AFFECTING IDLE:

1) Dirt in the idle jet.

2) A small speck of dirt in or near the upper of two tiny outlet ports of the idle system. This is the port (about the size of a fly speck) that you see just off the edge of the throttle valve when looking down from the mounting flange of the carburetor.

3) A faulty seal around the idle passage way between the upper and lower halves of the carburetor housing. This passageway is in the very center of the carburetor housing and is about the size of a drinking straw. If the gasket between the upper and lower housing is not completely sealed around this passageway, air can be drawn in and break the suction necessary to draw fuel up to the upper idle port.

4) A leaky float valve which provides such a rich mixture that it floods out the engine at idle RPM.

5) There is an air bleed hole in a small brass plug that is pressed into the lower face of the upper half of the carburetor that sometimes becomes blocked. This plug is located between the idle fuel jet and the venturi tube in the main throat of the carburetor and can be easily seen when the upper half of the carburetor is separated from the lower half. Sometimes a small speck of dirt lies on top of this small plug and interferes with the air being drawn in through the bleed hole to mix with the idle fuel.

MANIFOLD LEAK: You could have a vacuum leak in the manifold gasket or carburetor flange gasket. Some folks have been successful in diagnosing a vacuum leak in these areas by spraying some starting fluid around the manifold gasket and carburetor flange gasket while the engine is at idle. If the engine RPM changes at all while spraying the starting fluid, the gasket is almost certainly leaking.