carb adj on 80s 4.5 Merc.

[russ]

Have a  late 80s or so merc that has two carb adj. Can get it to run spraying gas in carb but cannot get carb set. When motor came to me both screws were turned in all the way.Looks like parts are N.L.A for the 4.5 Thanks Russ.

[seakaye12]

What is the serial number of your motor?

[russ]

serial number is 6499607

[seakaye12]

Does your carburetor look like this?

[russ]

No I made a mistake it is a 3.5 and has a mikunni carb on it.

[seakaye12]

OK.  Well as a general rule if an engine will only run with fuel injected into the carb….it is more likely a plugged up jet or needle/seat than a mis-adjusted screw setting.  So;  if you have not already done so….I would suggest cleaning the main jet thoroughly and checking the needle/seat for proper operation.  Have a look at the float level while you are at it.

according to  an aftermarket manual that I have here….the idle mixture screw should be 2 turns out from a gentle seat…..and the idle speed screw should be turned in two additional turns from the initial seat for a preliminary adjustment.

In the image below….#11 is the Needle/Seat.  #21 is the idle speed screw and #22 is the idle mixture screw. 

[russ]

OK thanks very much will try this all again.

[russ]

So the idle speed screw is also two turns out from seat or four turns out. Thanks Russ. It is staying running  now just trying to fine tune…

[Author]

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