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Uneven gas consumption

J

jclays

Regular Contributor
Filled up at the beginning of summer. Seventy five gallons 2 tanks. End of summer use. Fifteen gallons left on the port engine's tank. Six gallons left on the starboard engine's tank. Both tuned alike. Timing same. Plugs same condition. Any thoughts?
 
Are you sure the tachs are reading correctly, or is a sync used? Is the STB eng reverse rotation? Are the props identical except for LH/RH, including fouling/growth? You are seeing 9 gal difference out of 60 or 15% diff.
 
Tachs are standard not sync. Engine is reverse rotation props are identical. No growth or fouling diver cleans monthly.
 
A dirty flame arrestor caused that problem on mine; and brother was I embarrassed when I figured it out!

Jeff
 
I would check choke fully open when warm, and the clean arrestor. I've been in this mode before, including swapping carbs from one side to the other. Is most of this run time at cruise or trolling or ? Cruise settings should be at the same rpm; can you tell the engines are sync by ear?
 
two questions: 1) what method was used to base the "identical" caveat to the propellers and 2) have you measured the intake manifold vacuum across the rpm band, under load, for both engine?

On 1) above, unless both props have been thru a "prop scan like" assessment, you will never know.

On 2), the vacuum reading (vs RPM) will help you understand the load the engine is seeing as well as let you know how well its state of tune is.

Finally, you need to make sure the ignition advance curve is "matched" for each engine...
 
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