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  1. #1
    IDoSeaDoo's Avatar
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    Drivetrain noise/vibration, Tore it all down, still can't find the problem! HELP!

    2003 GTX SC 185HP motor in a 1997 Challenger. First ride of the season. Took boat out and it started strong, but before it could plane out, started missing on half the cylinders. Unplugging injector/coil on #1 cyl seemed to cause no change. #2 was more detrimental, and #3 shut the engine off. So I checked compression and got 130psi on all 3. Replaced plugs and boat ran great again. I started testing it on the water, and all seemed fine. Was running perfect. 5 miles later, I noticed a vibration, like the pump is unbalanced... slowed down and vibration seemed to improve. Kept going and a while later, felt a thump. I thought it was the Bass dropping on the 10" sub right beside the helm. Once the music died down between tracks, I noticed a weird noise, like a spun bearing. It sounded like a bearing without a cage, where the balls are going around, chasing the gap. I dropped the RPMs and started feeling the vibration more. The lower I dropped the RPM, the worse the nose/vibration got. Shortly after I noticed it, the engine started to struggle, and the Check Engine alarm came on the dash and beeped. I shut it down. Attempting to restart gave me the worst squeal grind ever. Coupled with the scolding beep from the MPEM, I decided to not press it again.

    My first thought was PUMP. Since before the first ride, I did change out the impeller for one out of a 2005 GTX. This thing was MINT. The boat pulled like a beast with 0 cavitation. I do have a metal wear ring in this boat. When I checked the pump though, I found that it turns smoothly. I even put it on an impact gun and turned it over fast and it didn't make any noise. The impeller does however have some wear around the blades, like they've been grinding the wear ring. The wear ring itself has some markings, and both are rusty, despite both being SS. The thing turns smoothly and quietly, even at the speed of a dewalt drill.

    I started taking apart the engine, thinking maybe it's the supercharger. I pulled the SC, and it turned out to be just fine. Washers and bearigns in perfect shape. Spins smoothly, quietly, and no play in the shaft whatsoever. Next, I pulled the oil filter and found aluminum chips in it. I'm not used to seeing this much debris in a 4stroke oil filter, so I figured it's bearings. However, I pulled the plugs and they looked perfect (just like after I changed them). I then did another compression test. Got 130, 130, and 140. Interestingly, 130 belonged to the two cylinders which mattered the least during my initial problem that was "fixed" after I put in new plugs. Cylinder #3 had the highest compression, being the cylinder that shut the boat off if I disconnected it's coil.

    Anyway, I pulled the motor, and both oil pumps looked good, aside from some normal scarring. Looks like some of those aluminum chunks made it though there, but the pumps are not destroyed. They definitely don't look new, but don't look destroyed either. I found no debris anywhere else in the motor. The oil had a slight silver sheen to it, but looked pretty good over all. I've definitely seen worse oil with more of a sheen on cars with bad oil pumps. Spinning the motor over with the starter sounds perfect, and I even saw a jet of oil shooting at where the SC gears would have been had I not had it removed. Turning the engine over by ratchet (PTO cover off) when it was out felt smooth and no play.

    I got as far as removing the valve cover and making sure the valve train looks perfect, and cam lobes look good. I couldn't remove the large aluminum caps on the bottom of the engine (need propane to loosen). But at this point, I'm guessing pulling it apart any further would yield no more answers. I'll probably find that the bearings are perfect, just like they were in 2015, when I last had this engine apart to check bearings, install ARP flywheel bolts and replace all valves to bulletproof the engine. I wonder if it really may have been the pump all along. Could I have maybe sucked something up? What about that dry bearing noise? I wouldn't call it "grinding" or "growling"... it was like a bearing spinning in a race that was a bit too large for it.... Could that have been the sound of the impeller hitting the steel wear ring? They are both scrathed up, and the impeller looks like it was rubbing against it. This pump was rebuilt about 150hr ago with a WSM kit...

  2. #2
    IDoSeaDoo's Avatar
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    Here's the pump and oil filter. The whole filter is filled with these shards of metal. This doesn't look right to me. The oil pump screen had some debris, looks like sealant material from where I last resembled it. Click image for larger version. 

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  3. #3
    SplishSplash's Avatar
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    Aluminum shards, probably spun a crank bearing or the thrust washers are gone and its eating into the aluminum. Did you check the crank for back and forth play?
    Your going to have to split the cases and asses whats gone wrong

  4. #4
    IDoSeaDoo's Avatar
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    If it's bottom end, any chance I can leave the head alone? I don't want to buy head gasket and bolts. It's hard enough convincing the wife to keep this boat

  5. #5
    IDoSeaDoo's Avatar
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    Seems like it's thrust washer. Lots of play in the crank. How bad does this look? Still lots if that bearing left, but it looks chewed upClick image for larger version. 

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  6. #6
    SplishSplash's Avatar
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    Well, it looks like it got very hot too, really discoloured.
    Thats not a crack in the crank in pic 2? Just a casting mark?
    Looks like oil starvation, one from the toasted bearing and two the collaspsed oil filter, which is usually indicative of water in the oil.
    Your going to have to pull the crank and see whats got to be repaired. I think you can get it out by just removing chain tensioner and the cam sprocket.
    Are you sure the prop did not come loose and walk forward pushing the driveshaft int the crank? Thats what usually destroys the trust bearings or the engine installed too far back.

    Being a 2003, I see what you mean about spending money on it. But they don't make them anymore so it kinda worth it if you like the boat.

  7. #7
    ncdoo's Avatar
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    Actually the bearing dont look that bad. The discoloration is mainly from the heat treating when the crank was manufactured.

  8. #8
    IDoSeaDoo's Avatar
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    Agreed, that same discoloration was evident on all joints. I removed the thrust washers and while one is ruined, it looks like it saved the block and crank. The oil pumps took a hit, but I was able to wet sand out the scars. The mains plastigauged within spec, so I think I will just order new thrust bearings and reassemble. I think maybe the engine was too far back or the prop worked itself loose. Click image for larger version. 

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  9. #9
    IDoSeaDoo's Avatar
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    So it turned out that three motor mounts failed. All three had the tops coming off... ordered some new ones.

  10. #10
    IDoSeaDoo's Avatar
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    Put new thrust washers on, and replaced the broken motor mounts only to have the thrust washer go out again within 10hr. Prop was/ is still tight on the pump, and motor was aligned. There was still a slight vibration in the driveline at wot, but we rarely went into those high rpm. Failure occurred at about 5400 rpm, calmly cruising...


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