Low compression
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Low compression

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    Default Low compression

    i have a 2002 hallet 255 mid cabin open bow with a hp500efi with 180 hrs. ive owned since 07 with 90 hrs. always thought it should perform a little better and seems to be slowing. with light load, light fuel, lab finish 26 bravo, slight chop lucky to see 70 mph (gps)@appx5k rpm . so i checked compression, reading 150 to 159lbs. the service manuel says minimum of 175psi. previouse owner and i baby this boat, probably doesnt have a half hour total @wot.it runs smooth and burns no oil. i thought i read somewhere these motors had some valve problems but i assumed that was under severe conditions like raceing. any thoughts????

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    Quote Originally Posted by ricks raft View Post
    i have a 2002 hallet 255 mid cabin open bow with a hp500efi with 180 hrs. ive owned since 07 with 90 hrs. always thought it should perform a little better and seems to be slowing. with light load, light fuel, lab finish 26 bravo, slight chop lucky to see 70 mph (gps)@appx5k rpm . so i checked compression, reading 150 to 159lbs. the service manuel says minimum of 175psi. previouse owner and i baby this boat, probably doesnt have a half hour total @wot.it runs smooth and burns no oil. i thought i read somewhere these motors had some valve problems but i assumed that was under severe conditions like raceing. any thoughts????
    The single biggest problem these engines suffer from is out of round cylinders. They are out of round from the factory. Sounds unbelievable, but it isn't. If it doesn't burn oil, consider yourself lucky. Its pretty normal for them.
    Drop BD Marine(user name) a PM. He can tell you if the numbers are good or not. I certain he has seen the compression PSI on more than a few of them And he pretty much knows when they are done, or going.



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    thanks will do. also on the oil issue i hear a lot of people say they(big blocks) burn a qt a day or every few hours. when i used conventional oil i would use a qt appx every 10 hrs+ but since using synthetic i might use a qt in a seaon (30-40hrs) then agian i typically cruise 28-3500rpm, maybe a few bursts wot for 30 seconds or so while onthe lake. had the same oil useage on my last 454mag, and my s/c 350 volvo.

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    The 454 Mag wasn't the oil consumer the HP 500 is know for. If you using that little, your lucky. May be because of the low amount of time you run it at WOT. but most use alot of oil.
    Like I said, Brian can give you the straight scoop.



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    Quote Originally Posted by ricks raft View Post
    thanks will do. also on the oil issue i hear a lot of people say they(big blocks) burn a qt a day or every few hours. when i used conventional oil i would use a qt appx every 10 hrs+ but since using synthetic i might use a qt in a seaon (30-40hrs) then agian i typically cruise 28-3500rpm, maybe a few bursts wot for 30 seconds or so while onthe lake. had the same oil useage on my last 454mag, and my s/c 350 volvo.
    Mines one of them! My 502 will use a quart in a day, if i put some miles on and run it hard a couple times. Its low hours also, and the plugs always look fine. This season is switched from Merc "dino" oil to 15w50 Mobil 1 synthetic, I am hoping this may trim the oil consumption a little...
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    Quote Originally Posted by ricks raft View Post
    so i checked compression, reading 150 to 159lbs. the service manuel says minimum of 175psi.
    Hard to believe 175 psi with 8.75:1 (listed) compression and the cam it has.
    Probably know this but just in case, when compression testing have throttle blade wide open, fully charged battery and better to have all plugs out to let starter spin motor fast and make all cylinder tests more consistent. Altitude can have slight effect on compression testing too....so I heard....I'm near sea level and never tested high up so I can't confirm the altitude thing. LOL.

    Now, the 525EFI uses a smaller chamber head so compression is a little higher, so maybe that's where the 175psi came from ????????

    Are you using 87 octane fuel ? Most 502's from Merc run much better with it because of ECU programming.

    Plugs, cap, rotor in 100% condition ?

    Water seperator/filter new ?

    Vacuum line to fuel psi regulator on and sealing ?

    Any tiny dings on prop ?

    Any gear you left on board and forgot about during the different tests? Kinda funny but it happens to most of us. LOL.

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    thanks checking in to it

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    Are you sure that your compression gauge is accurate? I have no idea if mine (old, made in USA ) is accurate but I'm usually just looking for consistent numbers.

    FWIW, on a PWC forum that I frequent, "they" always talk about inaccurate compression gauges.
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    Quote Originally Posted by dannyual777 View Post
    Are you sure that your compression gauge is accurate? I have no idea if mine (old, made in USA ) is accurate but I'm usually just looking for consistent numbers.

    FWIW, on a PWC forum that I frequent, "they" always talk about inaccurate compression gauges.
    it should be close i used it recently on my 98 work van 235K miles all read betwenn 168 and 174...

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