New Carb on a 3.0LX Mercruiser

[Summett]

I just installed a brand new (out of the box) mercarb on my '97 3.0LX mercruiser. My question is, are there many adjustments that need to be made upon starting for the first time, and would I be able to do them (or does a shop need to)?<br /><br />The carb "seems" sealed with everything included with it. And, there "seems" to be only two adjustments that i can see: throttle adj screw, and the idle adj screw.<br /><br />Is this something i can do myself, and if so any tips or assistance from anyone would be helpful (i.e. what to look/listen for, idle speed, which adjustment first, how much to adjust, etc.)<br /><br />Thanks in advance for the help!

 

[chiselchst]

Re: New Carb on a 3.0LX Mercruiser

(Edited cause I misread your post, and thought you installed a new ENGINE! MY Bad!)<br /><br />(If the idle speed and mixture screws are sealed, then you are not supposed to make any adjustments...emissions reasons.)<br /><br />The only adjustments you can make are idle speed, and idle air/fuel mixture.<br /><br />Idle speed ~700, then adjust the idle fuel/air ratio, maybe using a vacuum gage or tach - may have to re-adjust the idle speed again after these adjustments. Try to reach the the highest point (speed or vacuum) when adjusting. Then back out the mixture screw screw 1/2 turn.

 

[Summett]

Re: New Carb on a 3.0LX Mercruiser

Thanks Martinez! <br /><br />So i would pretty much need a vacuum gauge or tach with the idle fuel/air ratio to get it set right after i have the idle speed at 700?

 

[jaybirdtx]

Re: New Carb on a 3.0LX Mercruiser

Initial idle/air adjustment is approx. 1 1/2 turns out. Turn the screw in until it LIGHTLY seats, back it out 1 1/2 turns. Start your engine, and try to maintain approx. 600-700 RPM's by adjusting the idle screw. Turn the idle/air screw in, keeping count of how many turns, until the engine starts to choke down. Now, turn it out until the engine starts to choke down again. Remember how many turns it took to get it to do this and turn the screw in half way between the 2 points.

 

[Summett]

Re: New Carb on a 3.0LX Mercruiser

Thanks OBM! I have read in other posts that having the boat in the water idling is different than out of the water.<br /><br />I would be setting this out of the water at this time (i'm in MN) so would i still try and adjust it between 600-700 RPM's or a little higher due the fact that the prop wouldn't be pushing water?<br /><br />Thanks again for your help.