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Intermittent Engine RPM spikes

Marine Fuel Systems

Section - My marine diesel engine (VETUS Peugeot P25, 4-cyl, 65HP) runs smoothly at 1800RPMs, then, at ...
   
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  1. #1
    Ensign
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    Member Since : Jun 2017
    Home Port : Noordwijkerhout, Netherlands
    Curtevenna 10m motor boat
    Posts : 2

    Default Intermittent Engine RPM spikes

    My marine diesel engine (VETUS Peugeot P25, 4-cyl, 65HP) runs smoothly at 1800RPMs, then, at random intervals from 2 to 30 minutes, the RPMs rise by 100-200 for about a second then drop back to previous RPMs. This has been going on for two seasons with an apparent increase in the number of occurrences. The engine has 1600 hours, the boat is new to me (2 years). I had the fuel tank cleaned and the contents filtered. Also the fuel lines and pump cleaned. I replaced the fuel filter several times, after sometimes just 20 hours (to see if the number of occurrences of racing would go down, they didnt). The old filters never showed any signs of dirt. No water shows in the primary filter. Does anyone have any suggestions as to what might be the cause or how to troubleshoot this? Thanks!

  2. #2
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    Cap'n Ray's Avatar
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    Member Since : Sep 2011
    Home Port : SW Florida
    Boat's Name : "Curtains" (to be changed in the near future)
    1964 Chris Craft Roamer Commodore
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    I'm not a huge diesel expert by any means, but if the engines are electronically controlled, the possible causes go way up. Are there any common occurrences at all when it happens? Adding electrical load, turns, changes in water temp/ contents/ depth, crossing wakes etc? So many possibilities- just have to start eliminating one by one!

  3. #3
    Ensign
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    Member Since : Jun 2017
    Home Port : Noordwijkerhout, Netherlands
    Curtevenna 10m motor boat
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    Thanks for your reply. The boat's only 10m, no complex systems. Unfortunately, it happens while we are just motoring along without changes in speed, direction or other conditions; appears to be totally random. I have no clue how governors work, but that had been brought up as a possibility. I also wonder if dirty injectors would cause this. I added a can of Wynn injector cleaner but that seemed to increase the number of occurrences - might be a coincidence.

  4. #4
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    TimG's Avatar
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    Home Port : Olive Branch, MS
    Boat's Name : "WooHoo"
    1986 Cruisers Elegante 297
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    I would lean toward governor as well but you may be on to something with that injector cleaner, I would do it again. The cleaner may have broken loose some debris, also may have to blow out the lines.
    ~ on the hook ~

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