Holly 2 brl jetting

Deeds Pops

Recruit
Joined
May 18, 2017
Messages
4
I just installed a new 370hp 5.7 in my 2009 Glaston gt205, replaced the 5.0 220 hp. I reinstalled the holly 2barrel hoping to retain fuel mileage. I haven't pulled a plug to confirm yet but suspect lean running (don't want to do that to new motor). I also haven't cracked the shiny red paint on carb to check jet size. Boat runs primarily at or above 5200 ft above sea level.

Now here is questions. Anyone know for sure if that carb is jetted differently between the two engines? What all should I do to get max performance and mileage? Should I just buy a four barrel and be done with it? (Don't want to spend the money if I don't have to)
Thanks for any help I can get on this.
Pops
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,582
It would be best to check the motor with an Air Fuel Ratio meter, but doing this requires installing O2 sensors in the exhaust. Going from a 5.0 to a 5.7 with the same carb at sealevel would put you into a lean condition, but at a mile high it may just workout. Most boats get reproped to a lower pitch when going higher, but can also reduce the jet size.

Look at your plugs and see what color they are. If there white (and you have some hours on them) then your running lean. If there tan or brown color your doing good.

reinstalled the holly 2barrel hoping to retain fuel mileage ..... What all should I do to get max performance and mileage?

Always get a smile from me when I see mileage connected with performance. You get best performance when your motor has the best fuel to air ratio (12.8 to 13.2). If you want mileage you need more air, but this causes lean condition. Less air performance falls off and things carbon up. Mileage has very little space in the change, its a boat

BTW your in the wrong area but a mod will be here shortly and move it
 

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
Howdy Pops.

Moved this into I/O Non-Repair. It seems to be more a Can I Do This type question than a Fix It question.

Red paint - Is this a Volvo-Penta?
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,468
Red paint - Is this a Volvo-Penta?

Ayuh,.... That's My guess too,... Red paint, 'n a Holley carb, screams Volvo,....
 

Deeds Pops

Recruit
Joined
May 18, 2017
Messages
4
Yep it's a Volvo. I knew that would give it away. Thanks for the help. I have 7 hours on the new engine so it will be hard to see on the plugs. But it was just a concern as I really don't want to damage the new engine. Thanks again
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
While the 500cfm was perfectly sized for the 5 liter up to 5000 rpm, it is a bit small for the 5.7.

I would be skeptical about 370hp, the VP 5,7 carbed(2bbl) was 260hp. With the 4bbl it rises to about 280 - 290. What is your new engines WOT rpm range?
If you are using the 5 liter intake manifold, great. It is a very good 4 bbl manifold.
If you are going the 4bbl route, here is my choice
https://www.holley.com/products/mari.../parts/0-80552 Spreadbore 650
With just a bit of tinkering, the linkage attachments on your 2bbl will swap over to this carb. 650 is plenty more airflow than a 5.7 will need below 7000


5.0GL-A/B & 5.7GL-A/B Models
Volvo Penta #3858334 500 CFM Model 2300-2V
Pump Lever Clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.010-0.015 in. (0,254-0,381 mm)
Choke Unloader. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.300 in. (7,62 mm) Measured Lower Edge of Plate
Choke Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Notches Lean
Initial Idle Mixture Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3/4 to 1 Turn Off Seat
Main Jet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Power Valve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5
Float Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parallel to Fuel Bowl When Bowl Inverted
Choke Vacuum Qualification . . . . . . . . . . . . . . . . . . . .0.315 in. (8,00 mm) Measured At Lower Edge of Plate
Pump Cam Position (yellow cam) . . . . . . . . . . . . . . . No. 1 Hole of Cam and Throttle Arm5.0GL-D/E Models
5.0GL-C Models
Volvo Penta #3863242 500 CFM Model 2300-2V
Pump Lever Clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.010-0.015 in. (0,254-0,381 mm)
Choke Unloader. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.300 in. (7,62 mm) Measured Lower Edge of Plate
Choke Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Notches Lean
Initial Idle Mixture Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3/4 to 1 Turn Off Seat
Main Jet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Power Valve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5
Float Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parallel to Fuel Bowl When Bowl Inverted
Choke Vacuum Qualification . . . . . . . . . . . . . . . . . . . .0.315 in. (8,00 mm) Measured At Lower Edge of Plate
Pump Cam Position (yellow cam) . . . . . . . . . . . . . . . No. 1 Hole of Cam and Throttle Arm5.0GL-D/E Models
1. Idle mixture setting is non-adjustable for engines operated
in California.
Fuel Systems
122 VPA 7743454 English 09-2004
5.7GL-C Models
Volvo Penta #3863244 500 CFM Model 2300-2V
Pump Lever Clearance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.010-0.015 in. (0,254-0,381 mm)
Choke Unloader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.300 in. (7,62 mm) Measured Lower Edge of Plate
Choke Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Notches Lean
Initial Idle Mixture Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3/4 to 1 Turn Off Seat
Main Jet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Power Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5
Float Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Parallel to Fuel Bowl When Bowl Inverted
Choke Vacuum Qualification . . . . . . . . . . . . . . . . . . . 0.315 in. (8,00 mm) Measured At Lower Edge of Plate
Pump Cam Position (yellow cam) . . . . . . . . . . . . . . . No. 1 Hole of Cam and Throttle Arm5.0GL-D/E Models
5.0GL-D/E Models
Volvo Penta #3863242 500 CFM Model 2300-2V
Pump Lever Clearance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.010-0.015 in. (0,254-0,381 mm)
Choke Unloader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.300 in. (7,62 mm) Measured Lower Edge of Plate
Choke Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Notches Lean
Initial Idle Mixture Setting1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3/4 Turn Off Seat
Main Jet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.2
Power Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5
Float Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Parallel to Fuel Bowl When Bowl Inverted
Choke Vacuum Qualification . . . . . . . . . . . . . . . . . . . 0.315 in. (8,00 mm) Measured At Lower Edge of Plate
Pump Cam Position (yellow cam) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . No. 1 Hole of Cam and Throttle Arm
5.7GL-D/E Models
Volvo Penta #3863244 500 CFM Model 2300-2V
Pump Lever Clearance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.010-0.015 in. (0,254-0,381 mm)
Choke Unloader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.300 in. (7,62 mm) Measured Lower Edge of Plate
Choke Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Notches Lean
Initial Idle Mixture Setting1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3/4 Turn Off Seat
Main Jet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.2
Power Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5
Float Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Parallel to Fuel Bowl When Bowl Inverted
Choke Vacuum Qualification . . . . . . . . . . . . . . . . . . . 0.315 in. (8,00 mm) Measured At Lower Edge of Plate
Pump Cam Position (yellow cam) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . No. 1 Hole of Cam and Throttle Arm
1. Idle mixture setting is non-adjustable for engines operated
in California.
 

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
I just installed a new 370hp 5.7 in my 2009 Glaston gt205, replaced the 5.0 220 hp. I reinstalled the holly 2barrel hoping to retain fuel mileage.
Howdy,

You are going to find that fuel "mileage" is unaffected by the type of carburetor you install. AND, for that matter, it will be largely unaffected by the size of the engine! You may even discover that at a medium cruising speed (like you used to run at before with the smaller engine) you might burn a tad less GPH.

You need to put the "right" carburetor on that engine. If it's a 650 "double-pumper" etc so be it!

Your fuel mileage will be dependent on your right hand!
 

MBAKER

Petty Officer 1st Class
Joined
Jun 9, 2008
Messages
275
Actually there are many times a larger engine may actually use let carb jet. If all else is the same carb size and especially cam specs, the larger engine puts more draw on the carb and pulls more fuel through the same size jet. Just because an engine is bigger doesn't necessarily mean it needs more jet.
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
You need to put the "right" carburetor on that engine. If it's a 650 "double-pumper" etc so be it!

99.999999% of the time a Double Pumper is not a good choice for a marine engine.

Actually there are many times a larger engine may actually use let carb jet. If all else is the same carb size and especially cam specs, the larger engine puts more draw on the carb and pulls more fuel through the same size jet. Just because an engine is bigger doesn't necessarily mean it needs more jet.

Higher "draw" will also raise manifold vacuum, and may require a recalibration of the Power Enrichment circuit. A carb can also flow more air than its CFM rating, it just does so at the higher pressure drop(vacuum). Again, a carb significantly undersized can run a high enough manifold vacuum at WOT to close the power enrichment valve resulting in a lean out at high speed

BTW. the Holley 500cfm 2bbl carb, flows about 380cfm when flow rated like a 4bbl
 
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