Rochester quadrajet rebuild

bassboy416

Petty Officer 3rd Class
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Jul 9, 2013
Messages
79
Just rebuilt my 1987 mercruiser quadrajet. It was a 17080565. My question is that my mixture screws (the adjusting screws on the bottom of the carb 2 of them) were at different turns out. My rebuild kit said both should be 3-4 turns out. On my old one, it ran great at idle before sitting all winter, so I wanted to use the old settings. The screw on the left (needle?) near the choke assembly was 6 turns out... The other was 3 turns out... should I reset to this setting or go with what the manual said? any help is much appreciated... also, if I get it back on the boat is it easy to monkey with? how would I adjust on the water? the screws have to be turned with needle nose as they do not have a flat head slot they are just nubs stickin out. thanks for your advice!
 

alldodge

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Mar 8, 2009
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40,581
Just rebuilt my 1987 mercruiser quadrajet. It was a 17080565. My question is that my mixture screws (the adjusting screws on the bottom of the carb 2 of them) were at different turns out. My rebuild kit said both should be 3-4 turns out. On my old one, it ran great at idle before sitting all winter, so I wanted to use the old settings. The screw on the left (needle?) near the choke assembly was 6 turns out... The other was 3 turns out... should I reset to this setting or go with what the manual said? any help is much appreciated... also, if I get it back on the boat is it easy to monkey with? how would I adjust on the water? the screws have to be turned with needle nose as they do not have a flat head slot they are just nubs stickin out. thanks for your advice!

If all passages are clean and the needles and other items are close to new and not worn, they will be adjusted about the same amount of turns. Having one more turns out then the other would indicate that the passage way in the carb on that side is not as clean as the other. Other things that can cause this is compression is lower on one bank over the other. The amount of turns out is just used to get the engine running, afterwards they are used to smooth out the idle.

Adjusting the carb on the water would be the same as on muffs, there shouldn't be much different. If the engine slows down to much when in gear, then further adjustment may be needed, but this could also be the idle screw adjustment. I like using a vacuum gauge and adjust the motor. Adjust for maximum vacuum and smooth idle
 

gm280

Supreme Mariner
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Jun 26, 2011
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14,585
Maybe the reason one was adjusted out more then the other was because the carb needed cleaned. So go with the kits settings and go from there... JMHO!
 

bassboy416

Petty Officer 3rd Class
Joined
Jul 9, 2013
Messages
79
Went with the kits specs and it fired up and idled great... After warming up it surged a little bit so I monkeyed with the screws a little. I got it to where I thought it sounded better, but yeah..... Carb was dirty and a thorough cleaning made a world of difference. Go with the kit specs! they do that stuff for a living!
 

Ryan50

Petty Officer 2nd Class
Joined
Feb 17, 2010
Messages
109
I am about to rebuild my 87 quadrajet also. What kit did you use? I ordered the Sierra kit (18-7072) from iboats. I have done a few edelbrocks but I am a little nervous about this quadrajet.
 

bassboy416

Petty Officer 3rd Class
Joined
Jul 9, 2013
Messages
79
I ordered my kit off ebay using the serial number of the carb which ended in 565 I believe it was like 10474565 or something close to that. Very simple kit. Don't be nervous man its easy money. I had never done a carb before. The hardest part for me was getting the horn free from the rest of the carb. There is a youtube video by alpheus that lines it out super clearly. If you want a link I'll look it up for you. It goes through every single step very clearly. Yeah... I'm a youtube mechanic... whatever works!
 

NHGuy

Captain
Joined
May 21, 2009
Messages
3,631
If any of you have trouble I went beyond Alpheus video and bought a book. I have a pretty good understanding of the Quadrajet at this point. so ask if you have issues.
 
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