How can this happen
05-23-2017, 02:08 PM
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How can this happen
- So another bit of bad luck unfortunately here are the details maybe the OSO community can chime in so I can better understand what went wrong, here are the details
New HP500 carb stock rebuild, New gen6 block, pistons, rods, bearings, new oem cam from mercury, new intake, oil cooler, new EMI thunder dry exahaust etc.
Rebuilt stock heads , new springs valves retainers rocker arms push rods, lifters etc, castings were freshy magnafluxed decked etc
Had Motor put back in the boat took boat to ramp idled out of 5mph zone 5 minutes ran the boat up to speed 3-5k rpm for 20 minutes boat ran perfect returned home put the boat up on the lift, no alarms no overheat or oil pressure problems, like I said boat ran great
2 weeks later after lots of rain in NY decided to take the boat out after work, idled down my canal 10 minutes..... jumped on plane only brought up to max3000 rpm;s almost completely on plain and motor started stumbling and missing bad, limped to the nearest boat ramp pulled boat out. Less than 45 min on the new motor probably less than15 min above 1,200 rpm, My boat shop calls me with news that I have 0 compression on # 5 and # 7 cylinders, pulled heads and below are pictures of what he found, two bent exst valves that kissed each piston... what do you guys think
https://www.dropbox.com/sh/tlt8p1gf6...PE67ZEx_a?dl=0
New HP500 carb stock rebuild, New gen6 block, pistons, rods, bearings, new oem cam from mercury, new intake, oil cooler, new EMI thunder dry exahaust etc.
Rebuilt stock heads , new springs valves retainers rocker arms push rods, lifters etc, castings were freshy magnafluxed decked etc
Had Motor put back in the boat took boat to ramp idled out of 5mph zone 5 minutes ran the boat up to speed 3-5k rpm for 20 minutes boat ran perfect returned home put the boat up on the lift, no alarms no overheat or oil pressure problems, like I said boat ran great
2 weeks later after lots of rain in NY decided to take the boat out after work, idled down my canal 10 minutes..... jumped on plane only brought up to max3000 rpm;s almost completely on plain and motor started stumbling and missing bad, limped to the nearest boat ramp pulled boat out. Less than 45 min on the new motor probably less than15 min above 1,200 rpm, My boat shop calls me with news that I have 0 compression on # 5 and # 7 cylinders, pulled heads and below are pictures of what he found, two bent exst valves that kissed each piston... what do you guys think
https://www.dropbox.com/sh/tlt8p1gf6...PE67ZEx_a?dl=0
05-23-2017, 03:12 PM
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Drop box isn't opening for me anyway. Does it look like anything went out the exhaust? Without seeing hard to say but remember foreign objects can transfer from port to port and then blown out. Hydraulic roller cam correct? Check number 5 and 7 exhaust manifold. Wish I could open pic. Will try a shut down and reboot.
05-23-2017, 03:18 PM
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Was able to open up and see pics. Wtf. Got me... you check spring pressure on seat and open? Only thing I can think of. How many hours are on valves? Degreed cam? I feel bad for you!
Last edited by getrdunn; 05-23-2017 at 03:45 PM.
05-23-2017, 04:54 PM
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Any thoughts here guys. Nothing obviously went in through the intake ports. At least no evidence anyway. Fatigued exh valves? I have no idea.
Last edited by getrdunn; 05-23-2017 at 04:59 PM.
05-23-2017, 05:53 PM
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Were the lifters replaced ?...........seems odd...5 & 7 fire back to back............seems like a timing event
05-23-2017, 07:20 PM
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I have the heads at a new machine shop getting rebuilt , so I hope it is a valve guide issue that will be fixed once and done, With that being said it will be a nightmare if I put it back together and it happens again it will be a season ending disaster, what should I do to rule out a timing related issue before I run this motor again, this is my second motor in 12 months first one was wrecked by reversion I have to get this right
