Jetting?

W

waynerh

Seaman Apprentice
Joined
May 13, 2007
Messages
36
Greetings,
I have an OMC sterndrive (king cobra) with a 7.4L chevy engine.
I purchased the boat from a guy in Texas (800' elevation). I live in Colorado (5200') and have been told by the 4 Winns dealer and a performance boat shop that re-jetting is not necessary, but that dosn't make sense to me.It seems to be running rich.
Does anyone have opinion and expertize on whether I should rejet?

Thanks for all of your help!
 
Last edited:
Haut Medoc

Haut Medoc

Supreme Mariner
Joined
Jun 29, 2004
Messages
10,645
Re: Jetting?

Maybe it ran rich in Texas, too......;)
You should not need to rejet, maybe readjust the carb, which is?......
You may need to prop down to keep your WOT within specs......;)​
 
Bondo

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,082
Re: Jetting?

It seems to be running rich.
Click to expand...

Ayuh,.........

I guess if you don't Look,....... You'll never Know...................:rolleyes:
 
StangLX302

StangLX302

Seaman Apprentice
Joined
Jul 18, 2007
Messages
38
Re: Jetting?

If it were me, and it was running rich as you say, I would tinker with it. You can order a Holley jet kit http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY-36-181&N=700+115&autoview=sku and go down 2 sizes at a time and check your MPH with a GPS so that you can gauge performance. Don't go too lean or you'll start burning holes in the pistons. Also, pull the spark plugs and see how it's doing after a run. Black = too rich. White = too lean. You want a reddish/brownish color. Also, BEFORE you start playing with jetting, make sure your ignition timing is spot on, your idle mixture is set properly and everthing else (cap, rotor, plugs, wires, flame arrestor clean) is up to par.
 
W

waynerh

Seaman Apprentice
Joined
May 13, 2007
Messages
36
Re: Jetting?

HI Stang,
Thanks for the link! Is the auto jets the same as the marine? The dealer told me they are different.
Wayne
 
StangLX302

StangLX302

Seaman Apprentice
Joined
Jul 18, 2007
Messages
38
Re: Jetting?

Hmmm... I've never heard that, but I would call first before you order just to double check.
 
W

waynerh

Seaman Apprentice
Joined
May 13, 2007
Messages
36
Re: Jetting?

Hey Stang'
One of the first things I was going to do was bump the timing, but the manuel says that it's not adjustable.
Wayne
 
StangLX302

StangLX302

Seaman Apprentice
Joined
Jul 18, 2007
Messages
38
Re: Timing

Re: Timing

Check back by your distributor base there should be 1/2" bolt holding the clamp down. Then check the front by the harmonic balancer. There should be marks (lines) on it with ATDC and BTDC numbers for the timing and a pointer afixed to the timing chain cover (or real close by) which would point to those lines when a timing light is shined on it. If this is the case, it is adjustable. Try to get ahold of a different manual and see where it's supposed to be set at and leave it at that. Any higher and it'll deisel when you shut it off and cause other (expensive) problems as well. too low will also cause problems too. Also, when you adjust and check it at idle, you have to temporarily plug the vacuum advance, if so equipped.
 
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