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How do you tune a 1973 65 HP Evinrude?

C

code1p36

Regular Contributor
I just replaced the powerhead of my 1973 65 HP Evinrude (65373R) and put on new coils and cleaned the carbs. It is a 3 cylinder with 3 carbs. The top carb has an adjustable needle and the two lower carbs have an adjustable screw in place of where the needle is of the top carb. Can someone step me through the proper tuning technique please? I already have all 3 carbs synched in regards to throttle linkage and choke (they are all in the same position). It is has a jet on it and I will be running the river mostly.

Thanks!
 
The 73 -----65 HP did not have any adjustable low speed mixture needles.------------------It was equipped with a fixed orifice.------The screw on the bottom 2 carburetors is a " plug " and not an adjustment.---The top carburetor is from a 72 -60 HP ?? or a newer 75 HP model.------You best bet would be to find another top carburetor for a 73 model !!
 
The top carb has part number 321253 and the lower two have 318505. Not sure what the top carb is but it looks like the two lower ones are from a 50 hp. This has been a project so I will be putting the correct set of carbs on it asap. Thanks for the help!
 
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Each carburetor basically feeds one cylinder and one cylinder only.----------There for you must have the 3 identical carburetors and the correct ones for your model year.
 
I received the correct carbs now and they are cleaned and ready to install. The fixed orifice were just barely seated when I received them. Should I seat them the same? Once I get them all synced up and opening at the same time what is the next step? How far open should they be when the mark on the cam throttle touches the roller? I see timing marks on the flywheel, does the timing need to be set? This powerhead was just installed from another motor. A start to finish tuning sequence would be appreciated! I have tuned single engine carbs but never 3 carb setups. Thanks in advance.
 
Grab the factory manual from this site. This is a must.
I have the exact engine you have, so I could take some pics if you need it.
I already have some, from when I did my carbs over 4 years ago.

Oh and those jets should not be loose!
 
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You need to understand that the carburetors have fixed jets.---------------So there is no adjusting ( tuning as you appear to call it ) that can be done by you.-------------At idle all three throttle plates must be closed !!!---------When the cam mark touches the roller that is the point where throttle plates start to open.-------------Ignition timing is fixed at the factory and usually is " bang on " unless it has been tampered with.---Some folks start adjusting stuff without a manual and that leads to all kinds of trouble.
 
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