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Merc 525 help???
I have a 525 efi motor is poping under a load and has no power. i switched out the computers theres no difference fuel pressure is 40psi did anyone had this problem before please help thanks..
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I don't know the spec but that fuel pressure seems low. I would expect around 55. Lean mixture can cause a backfire through the intake. But I would guess you have a burned or dropped valve. Possible due to the lean mixture if I'm right about the fuel pressure.
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Originally Posted by vinnysrt8
(Post 2847127)
I have a 525 efi motor is poping under a load and has no power. i switched out the computers theres no difference fuel pressure is 40psi did anyone had this problem before please help thanks..
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yes i have twins in the boat they r both at 40 psi for fuel the other motor runs great. it has 180 hours on it.
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40 sounds about right the specks are normaly 38 psi with vac hose on and 43 hose pulled off. still pull off you fuel filter and dump it in a glass jar or a clean coffee can and look for water or dirt. also check the ground cables to the batteries and engines make shur they are tight and clean. Was this your first run this year after sitting ? could be some left over old gas.
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pull the valve covers
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This started happing last year i change the fuel filters last year no diff and today i pulled the valve cover off to see if there is a bad spring but they all look good
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If it's only doing it under a load, then start looking at the ignition system. Check the coils to be sure they are all getting power. Also, check all of the plug wires real good. Pull the plugs and make sure that none of the porcelain is cracked. Usually, ignition problems only show themselves under a load.
Eddie |
Originally Posted by vinnysrt8
(Post 2847293)
This started happing last year i change the fuel filters last year no diff and today i pulled the valve cover off to see if there is a bad spring but they all look good
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i agree with boat tec
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Yes i did a tune up when it started happening did no change
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all the plugs look good and the coil all has power.
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the compreesion on the motor is 160 on all 8 but i didnt do a leak down test ill do that today.
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Might sound too easy, but change the map sensor. we go through a ton of them. Check the small black ground wires attached at the bell housing stud.
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I had the same problem with my 500 efi's after storing it all winter. I replaced the fuel regulator and all was good. It was a reasonably easy job...good luck
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Well today i put the boat in the water to test it out after changing the wires it sounded good on land went for a quick ride it ran good for about 15 min it was at 5400 rpm then the oil pushed out of the dipstick so i am thinking there is some blow by and that why its running like crap any input thanks.
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Another thing is the oil temp goes sky hight it is at 250+ as the other motor it is at 200..
the water pressure is good water temp good oil pressure good. |
Was the engine ever rebuilt ?
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Originally Posted by THLWL
(Post 2848238)
Good luck is all I can say. My popping sound was stuck valves in head. I've stuck the exhaust valves in the heads for the third year in a row and am still under 200 hours on engines. NO ONE can find the culprit. I've now had the heads rebuilt by the third diff shop. Merc Racing has been no help. I originally had capt call exhaust and they blamed it on that. The last 2 years, I've had Merc original exhaust and still sticking. We've done it all to the heads - enlarged tolerances, etc. Hope your prob is not with the valves sticking cause IT SUCKS! BTW, if the popping sounds like it's thru the intake (like mine), it can be an indication the exhaust valve not opening properly to let out fired exhaust. And 5400 on RPM's, my rev limiter alarm goes off at about 5100.
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Originally Posted by boat teck
(Post 2847941)
Was the engine ever rebuilt ?
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Originally Posted by THLWL
(Post 2848278)
But you also need to check and make sure it's not just a weak or broken valve spring or faulty lifter which would still cause a popping sound and also allow for a good compression check reading. Believe me, I've been down this road for the last 3 years.
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A flat cam will cause popping through the intake.(I know 525 efis' have roller cams). It won't always show up in a compression test (cranking). You loose lift (and duration) on the exhaust valve, then the exhaust charge cannot fully evacuate from the cylinder, then it compresses and pops throught the intake when that valve opens next. More promenent at high rpm obviously. Pull the valve cover crank the motor (fuel disabled) and watch the rockers. Good luck
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Originally Posted by THLWL
(Post 2848238)
Good luck is all I can say. My popping sound was stuck valves in head. I've stuck the exhaust valves in the heads for the third year in a row and am still under 200 hours on engines. NO ONE can find the culprit. I've now had the heads rebuilt by the third diff shop. Merc Racing has been no help. I originally had capt call exhaust and they blamed it on that. The last 2 years, I've had Merc original exhaust and still sticking. We've done it all to the heads - enlarged tolerances, etc. Hope your prob is not with the valves sticking cause IT SUCKS! BTW, if the popping sounds like it's thru the intake (like mine), it can be an indication the exhaust valve not opening properly to let out fired exhaust. And 5400 on RPM's, my rev limiter alarm goes off at about 5100.
So how did it run this weekend?? |
Originally Posted by txriverrat2001
(Post 2848383)
So how did it run this weekend??
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I am gonna take the heads off this and ill get back with u guys on whats wrong..
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Originally Posted by vinnysrt8
(Post 2849033)
I am gonna take the heads off this and ill get back with u guys on whats wrong..
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no i didnt change the mechanical fuel pump b/c it is showing a steady 40 pounds.
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When you did the tune up,did all the plugs look the same or was one or more different?If a valve was stuck open and hit the piston,compression would be low (or 0) in that cyl.I'd check that ign system like Mr Young suggested.
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when i did the tune up all the plugs looks good........
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