Pri.73
Sec.81
P.v. 5.5

Try this and see if it works for you

Sent from my SM-G930T using SoCal Jet Boats mobile app

You got that without a list number?

Skills.

GT

Pri.73
Sec.81
P.v. 5.5

Try this and see if it works for you

Sent from my SM-G930T using SoCal Jet Boats mobile app

Sent from my SM-G900V using SoCal Jet Boats mobile app

Number should be on the choke horn. If it's a 4779 it's a 750. If it's a 4781 it's an 850.
Kinda looks like an 850 to me.


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If the carb hasn't been touched, it probably has size 80 main and secondary jets and a 6.5 power valve. You should probably change to at least a 5.5 power valve. They only come in 1/2 sizes. (4.5, 5.5, 6.5, etc.)
As far as jetting goes, run what's in it and check the color of your plugs. If they show a medium brown color it's good. If they're light gray or white, too lean. If they're black, too rich. You get the gist.
Holleys website sells all the parts for it.
You have an 850 double pumper.


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Dual power valves,  both 6.5".

Primary jets would have been 80,  secondary probably 78.

I would go 80 square with a 5.5 power valve on the primary and a 4.5 on the secondary.

This will get you silly close.

The one thing to keep in mind is that a jet does not need to pull a gear. You have to think of the fuel curve in reverse.  The engine has virtually no load until the impeller loads up,  like over 4,000 rpm.

Staggering the power valves makes for a smoother transition.


JMHO...

Sent from my SM-G900V using SoCal Jet Boats mobile app

To truly read spark plugs for an air/fuel indication an otoscope is needed. New plugs must be used and after a few hard pulls/passes the engine needs to be shut down ASAP. To really see deep down inside the plug shell at the color ring captured on the porcelain cone, you need an otoscope ( lighted magnifier) to truly see it, the naked eye with natural or florescent light is not enough to truly see the color ring. Color on the plug tip or shell base can only tell one thing….problems, not an air/fuel ratio indication.