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Old 01-16-2006, 10:44 AM
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Default fuel consumption/ efi

just finished first 300 miles on 38'top gun 2 x 502 mag mpi.

1/2 of that at WOT the rest ast 50ish mph 4200 rpm... plus the usual docking etc... milage consisted of multiple round trips to local island for lunch... about 33 miles total... plus a couple extended runs in early trials after assembly.

max speeds for 15 miles at a crack is 65 @ 5000 rpm

total fuel consumption for 300 miles was 223 gallons... and here is the part i love ( god i love efi...) port engine 111 gallons, starbord 112.... less than 1 % deviation....

i have no idea whether these are good numbers or not but this mpi system is the cats ass in this application.
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Old 01-16-2006, 07:30 PM
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Default Re: fuel consumption/ efi

Sounds like typical mileage for efi motors. What kind of oil temps were you seeing after 15 miles at wfo? Stock merc coolers are pretty small,If I was guessing I'd think you were at 300 degrees . You will definately be needing a drysump oil system if that was just your trial run ,Smitty
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Old 01-16-2006, 08:31 PM
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Default Re: fuel consumption/ efi

would be interested in "hours" ..... I have been watching fuel consumption in my 311 with 454mags ...Carb of course ....last cpl of test ... 111 gal/10hours ..... I also have 13GPH and 15 GPH .. 100 gal runs ... no 15 mile WOT's but some WOT running .... and general running around .. idle ..docking ..cruising ...(34-3800) about 50 mph ..
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Old 01-16-2006, 09:33 PM
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Default Re: fuel consumption/ efi

oil temps 240. discovered early on that engine bay ventilation sucked. so took a couple pcs of 2 x 4 on edge and closed the hatch on them so hatch tite but well vented. that made evrything MUCH better so permenant soultion in the works... interesting thing i discovered years ago on small production race cars and that was that air across the oil pan played a HUGE part in oil temps. fitted realy trick spoiler one day and oil temp hit the peg so fast thought gage was broken... wasn't,,,had just sealed bottom of car so well that no convection cooling. figure exactly what is/was happening here... stagnant 120 deg ( or more) air and the cooler inadequate EXACTLY as you say, made for BIG temps initially. . once got some moving air, cooler size and temps were just fine. i use that mobil 1 delvac.... has AMAZING shear numbers and abilty to deal w/ big temps.



can't deal w/ fuel vs hours... record keeping would be impossible. gps milage much more accurate but can extraopolate... at 1.37 mile/ gal that 15 mile 1 way trip takes me about 15 mins depending on sea conditions... so figure for easy math figure about 11 gals to get there times 4 is 44 gal/hour for both motors or about 1/2 that PER motor or 22/hour at WOT.

VERY rough figure but thats it.... at anyrate...VERY happy with whole deal. boat had " pro built" 454 carbs in it when prev owner had it... nowhere near as fast and milage so bad was scary... after 10 or 15 hours, oil would have so much fuel in it was worried it would just explode the pan off it... he just couldn't undertsand why he couldn't keep cams in it... or , as it turns out, bearings either.
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