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low WOT on mercruiser 5.7 with 19p prop

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low WOT on mercruiser 5.7 with 19p prop

Old 05-18-2013, 06:29 PM
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Default low WOT on mercruiser 5.7 with 19p prop

hi guys new to the site. just wondering bout my boat an WOT i have a 1986 21' liberator with a 5.7 260hp an a alpha 1 with 1.47 gear an a ss 3 blade 19 pitch prop an im seeing bout 3,900-4,000 rpm at WOT i feel like it should be more any in put would be great thanks
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Old 05-18-2013, 10:06 PM
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first check ignition timing. not just initial lead. you need about 30 degrees at WOT. then compression test, condition of carb, fuel filters, pickup in tank ... but you should be have to pull back on the throttle at 5000 with that boat with a 19 inch prop.
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Old 05-18-2013, 11:02 PM
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The quadrajet 4 bbl on my 260s were very sensitive to the cleanliness of the bronze fuel filter inside the carb behind the large nut that connected the fuel line.
Stock the engines were meant to turn 4400-4600 r.p.m.s
Follow Derek's advice and go from there.
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Old 05-19-2013, 08:34 AM
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thanks guys for the help. the carb just got rebuilt this week after i changed the both fuel filters last week an didnt make any difference but i will check the timing today because i figured something wasnt right because my last boat was a 91 21' maxum with a 4.3 an a14.5 19 pitch prop an it would turn 4;800 wot. i just bought this boat bout a month ago an was told the motor in it was newer because they over heated the old one so with that being said do u guys think i should run all the vavles an make sure there all at zero? im just trying to get this thing to run rite because the way its running at 4,000 rpm wot im getting like 48-50 mph on the gps speedo app on my phone an the boat speedo is really close to that its like 3 mph off. i have a built 355 with vortec heads an 536 lift cam all roller top end that im dying to throw in but many ppl told me not to because the alpha 1 out drive wont take it it made 450 on the dyno but thats with timing at 38 deg an a 750 cfm double pumper i mean i could detune it with smaller marine carb an less timing what u guys think ?
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Old 05-19-2013, 02:15 PM
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so i just checked the timing an it spot on after a little more investigation i checked the distributor cap an noticed there was a screw missing an 2 of them were rusted bad so after some pb blaster an a little tapping on them i got them off an found the distributor cap to be moist an corroded an the rotor the same then i checked the plugs an there a little on the brown side but they seem to be firing so i think im goin to spend the money an do a complete tune up an hope for the best
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