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Engine racket, no oil to rockers

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  • Engine racket, no oil to rockers

    Took the boat out Friday afternoon to go fishing and was cruising on out doing 18 kts at about 3200 rpm and the boat started slowing down, I just thought that the throttle was drifting back, so I kept pushing it back up. Then I noticed that the fuel efficency had dropped and all of a sudden engine started making noise and lost all power. Ended up having to run it back to the slip that way. Came back Sat evening and pulled a valve cover off and started the engine and there is no oil coming up to the rockers and there are a lot of metallic noises inside the engine. Engine is a Mercruiser 350 Mag MPI. Rebuilt heads and new lifters. Looking for some insight as to what went wrong. I have already figured that my season is over and plan on pulling the boat and engine soon. Thanks.

  • #2
    Lose of oil pressure will cause the lifters to deflate and oil loss to the rockers. Power loss will also be a result.
    Atlantic City, NJ
    1982 Cuddy, Rebuilt 351 .060 rings, Edelbrock carb

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    • #3
      According to the gauge, it did have around 20PSI of oil pressure and it did not overheat on the slow cruise home.

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      • #4
        20 PSI sounds low with the possible exception of having just pulled her back to idle after an extended hard run, then it should increase as oil temp cools. I don't have this engine and it sounds GM based so not familiar with what acceptable oil pressures are. First impressions are oil pump issue, rolled bearing resulting in bearing/crank/cam damage, oil level low. Have you verified oil level, inspected the dipstick for metal particles in the oil, and smelled the oil for a "burnt" smell?
        C Rhodes
        26' Mackinaw - 1990
        351 Indmar (1990-2006: Great Engine)
        351 PCM (2006 - Current)
        Southport, NC

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        • #5
          Yes, it is a GM based engine. It was only idling at about 600 rpm on the way back and had to run it that way for 2 hours to get back. Occasionally I could hear the rpm dip for a second. I have been coming to the conclusion that it may be a spun/rolled bearing as well. Oil level looks good, did not notice any metal particles on the dip stick. Didn't notice a burnt smell, but was not exactly looking for that either. Will check again when I have a chance to get down to the boat.

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          • #6
            Before writing off the engine guess we should check the basics. Is timing still the same and does it change with increasing in RPM? If timing retarded, at least the advance function, it could explain the loss of power (but this would not explain reduction in oil pressure). Manual verification of the oil pressure would be nice. Not knowing how your electronics are set up, if they are reported through a computer the computer could be messing with both your timing and gauge values. (Had something similar happen on a Ford Windstar.) Were the other gauges reading normal? It may be a long shot but best to check the cheap stuff first.
            C Rhodes
            26' Mackinaw - 1990
            351 Indmar (1990-2006: Great Engine)
            351 PCM (2006 - Current)
            Southport, NC

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            • #7
              Thanks for the advice. Tried to pull it last weekend but had a blown trailer tire, so that will have to wait until the new tires come in. Base timing was set per the manual, the computer handles everything from there. There is definatley a metallic ping when it is idling and there is no oil coming to the top of the heads. Only ran it for 30 seconds or so on Saturday. Once I get the boat out I will be pulling the engine and plan on pulling the distributor and oil pan and will go from there

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              • #8
                My opinion in order of probability.

                1) Wiped camshaft from new lifters on a used camshaft. (If they are flat tappet hydraulic lifters. Disregard if roller). Did you use a zinc additive? Why did you replace the lifters in the first place? Is there shiny silverish ick at the rear drains?

                2) Spun rear cam bearing.

                3) One of the three oil galley plugs in the front of the block came out.
                1980 pilot house 351
                1988 260 predator 408

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                • #9
                  Was having a hard time adjusting the valves with the old lifters. Was trying to adjust them to spec with the engine running, which is one full turn after zero lash. Some of the valves I was unable to adjust any further than a half turn and no matter how slow I adjusted, the engine would just shut off. After researching, I went ahead and replaced the lifters and adjusted them to spec with the engine off and it ran perfectly after I sorted the electrical issues. And these are hydraulic roller lifters. (I was using the zinc additive in the oil for the old 351, thanks to this forum). New tires were mounted yesterday but going away this weekend so not sure when I will get it out. Thanks for the tips.

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                  • #10
                    You cannot adjust new hydraulic lifters until they are pumped full of oil, the lifter piston will collapse. I run the rocker nut down until the play is eliminated (do not compress the spring in the lifter body) and then spin the oil pump with a drill until oil runs from all of the rockers. You may need to rotate the engine while running the drill to get oil out of all of them. Finally, adjust the rockers with 1/2 turn of preload.
                    Steve
                    1998 260 Mackinaw Sea Maxx 5.7 HO TBI 12' Klamath w/ 20hp Tohatsu EFI

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