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318 Edelbrocks and fuel guzzling

Fish Stix

Fish Stix

New member
Hi guys - as always - I value your collective knowledge and insight.

I have a Trojan F32 twin engine that's been running well on new Edelbrock carbs, and pertronix distributors. The problem is that on a 30 NM trip, the starboard side used 43 gallons, but the port side used 33 gallons. Quite a difference. And not exactly fuel efficient - at 0.7 and 0.9 MPG per side, and an overall of 0.4 MPG For both. Bottom was clean, sea surface flat, trim tabs deployed and trimmed, etc.. It's not that big a boat, and I was running 3600 for 15 to 17 kts. Those are some really bad numbers.

Thus the questions:

For the imbalance - I must have engaged the secondaries on the stbd motor for the 10 gallons for extra gas. Is there any other reason for such a disparity in gas usage (43 vs 33)

For overall guzzling - wow. I should look at the plugs for color (burning rich), and maybe pull the boat to get an actual weight, but what else should I look for? I know there's a ton of info out there, but what seems likely?

Thanks & Stay Safe!
Brooks
 
I should look at the plugs for color (burning rich)
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Ayuh,..... That would be the 1st thing I'd do,......

Do a run at 3600, slow quickly, 'n kill the motor asap,.....

The plug color changes if ya idle or run real slow for awhile, 'n ya want 'em at the color they're runnin', at the rpm yer checkin',....
 
I would also make sure the engines are 'tuned up' and get some reference data....verify the timing advance is functional and consistent on both engines...would also record intake manifold vacuum across RPM range.

What will the engines turn at WOT? 3600 RPM seems a bit high to me for cruise....

I would then consider retuning the carbs...am would think they would be pretty rich for a 318...
 
makomark said:
............. verify the timing advance is functional and consistent on both engines...would also record intake manifold vacuum across RPM range.
Click to expand...


Ditto Mark's comment.


Look up your OEM ignition advance curve, and then make sure that each ignition system is delivering that curve.

I'm referring to the Progressive advance and the Total advance at the prescribed RPM..... not just BASE advance.
 
i have a 31' uniflite with the same engines and have 1 edelbrock 1409 and one original Carter ATB. I have fuel flow meters, and I find 2700 rpm is great for cruising for me. I do 14knots and use 17 gallons per hour combined. The faster you go over hull speed the more fuel you use. My Edelbrock does about 25% better fuel consumption than the Carter
 
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