Click for Llebroc Click for JetForums Click for Oceanco Click for Nordhavn Click for Lurssen

Can't believe this genset wasn't over heating...

Discussion in 'Technical Discussion' started by Pascal, Jun 25, 2017.

You need to be registered and signed in to view this content.
  1. Pascal

    Pascal Senior Member

    Joined:
    Feb 29, 2008
    Messages:
    3,425
    Location:
    Miami, FL
    whenever i replace an impeller i always fish out the pieces, usually at the heat exchanger inlet. Takes just a few minutes. I ASSumed others do the same.

    Long story short... been running an 2009 84 lazzara for about 9 months now. The two onans 27.5 have never run hot but have always been a little louder than they should.

    So today I decided to check the heat exchanger inlets. Stbd only had a couple of pieces coming from the existing impeller which I replaced

    This is what I found in the port heat exchanger inlet. It was all packed in the 1" inlet, not even in the exchanger itself... impeller was intact son I didn't replace it.

    I have no idea how enough water made it thru to keep the coolant and exhaust temp in the green... and we put almost 1000 hours on each genset.

    obviously diesels whether gensets or mains have quite a bit of cooling reserve

    IMG_5496.JPG
  2. 30West

    30West Member

    Joined:
    Nov 14, 2016
    Messages:
    125
    Location:
    Holland, Michigan
    How about not only failing to fish out the pieces, my boat came to me with 12-yr-old impellers, originals. I'm pretty sure it was the scoop strainers keeping the engines cool during my 500-mile race home, not the shredded impellers. Good thing we were in a hurry. I fished the pieces out of the system, replaced what was left of those impellers.

    Yesterday I got to the generator, 100 hours and the bolts had obviously had a wrench on them, figured I was just going to replace it for baseline purposes, but it too was missing two vanes. This was a boat maintained by a professional yacht maintenance service at an expensive marina, not just some owner DIY failure. Hopefully not too many more surprises to come, just a lot of catching up on routine maintenance.
  3. olderboater

    olderboater Senior Member

    Joined:
    Sep 2, 2013
    Messages:
    4,107
    Location:
    Fort Lauderdale
    No, this was a boat you were led to believe was maintained by a professional yacht maintenance service. One of two things is the truth. Either the owner didn't contract for these services or contracted and they weren't provided.

    Every used boat had perfect maintenance until you ask for the logs and receipts. Then it often falls apart. Often people use yacht maintenance services but only for problems they report to the services and don't get routine or complete maintenance done.
  4. rcrapps

    rcrapps Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    4,875
    Location:
    Jax FL
    When any of our maintained boats loose an impeller part, I find all pieces and super glue them back together to prove I reclaimed all the parts. Logs are maintained and a true impeller life to expectations are ensured.
    350 hours on a 17-20KW, NL is about the norm for an impeller up here with all the river silt.
    We strive for gen-set oil changes between 200 to 250 hours. We have learned witch gen-sets get new impellers every oil change or every other oil change. So far in many years, were not to far off.
    StJohns river grass & debris contribute to these early demises. It's a feel for the boat and owners operation that helps drive our schedule.
    All gen-set raw pumps are replaced (new) every 1000 hours. We don't F**** with rebuilding them, the warranties from the vendor covers the owner better than I can.
    However, there are a couple of cores rebuilt as spares as emergency pumps that can be used while deployed. There is nothing worse than a call, the gen-set is down, guest are pissed.

    The most demanded on comportment of a ship is the light plant. Spoil it and take care of it well.

    Pascal learned it when he had to rotate gen-sets for false oil pressure alarms and shut downs (issue months or longer ago).
    Odd both had the same problems but he fixed it, on both sets, improved the system with real pressure gauges and can better manage any oil alarms in the future.

    Raw water is a great issue on cooling our gen-sets. Don't cut corners.
  5. 30West

    30West Member

    Joined:
    Nov 14, 2016
    Messages:
    125
    Location:
    Holland, Michigan
    Hard to know exactly in this case, maybe the owner didn't want anything but fluids and filters for 12 years. The maintenance company left a large sticker in the engine room with their logo on top, and detailed the fluids and filters changed that spring. And there was a card in the galley with the same info. When I called the company they said they hadn't worked on that boat for years, but their sticker and card were on the boat.

    I'm changing the fluids, will send samples to Blackstone and find out where I stand. So far, all the fluids look and smell lightly used.
  6. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    9,650
    Location:
    Fort Lauderdale
    I replace genset impellors annually, I've found most don't go 2 years without losing a vane or two, regardless of hours...... genset impellors are cheap and quick to replace.....mains I'll go 2 years or 200 hours. Maybe more hours if they're the large cat/man etc ones.....but never more than 2 years.
  7. Danvilletim

    Danvilletim Member

    Joined:
    Oct 30, 2011
    Messages:
    319
    Location:
    isleton, ca
    So what pieces do you need to remove to fish out vanes?
  8. Pascal

    Pascal Senior Member

    Joined:
    Feb 29, 2008
    Messages:
    3,425
    Location:
    Miami, FL
    On almost every genset I ve used the pieces end up just downstream from the raw water pump at the heat exchanger inlet. Pull the hose and open the end cap... takes 5 minutes.

    I usually get about a thousand hours on impellers and 2 or 3 years. Hard to prove but I think the key is regular use as it prevents them from takin a set which is what cracks the vanes
  9. captholli

    captholli Senior Member

    Joined:
    Jan 4, 2010
    Messages:
    622
    Location:
    In The Bilge
    +1 ,
    You hit the nail on the head exactly. Other than really silty water that will wear the impeller as well as the cam plate and bronze housing the biggest enemy of an impeller is lack of use and the rotational "set" that Pascal stated.
  10. Pascal

    Pascal Senior Member

    Joined:
    Feb 29, 2008
    Messages:
    3,425
    Location:
    Miami, FL
    I don't silty water really affect them much. We often run in shallow water. Anchoring in water only 3 to 4 feet deeper than the wheels as we do most of the time when we reverse to stop we kick a big sand or mud cloud and that gets sucked on no matter what Every time I back out out our tee head we re turning in a mud bath. Impellers don't see to be affected
  11. captholli

    captholli Senior Member

    Joined:
    Jan 4, 2010
    Messages:
    622
    Location:
    In The Bilge
    Churning up the bottom while maneuvering to drop the hook is a bit different than sitting in turbid waters in Turtle Bay for a week or two on the hook or anchoring off of a river mouth in Brazil. You'll go through impellers every week and water maker filters every few hours or so. Sand and silt acts as an abrasive and wears all components in the raw water circuit down in rapid succession. We took two Feadships up the Amazon river a few years back and had to divert and jury rig the large fire and ballast pumps to the Gens due to the impellers being chewed up from the silt and sand. We wound up doing the same for one of the mains as well.
  12. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    9,650
    Location:
    Fort Lauderdale
    The Mississippi is pretty bad too and you'll even eat up the raw water pumps in a few years there.
  13. rcrapps

    rcrapps Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    4,875
    Location:
    Jax FL
    Yep, this is what I've been saying about the silt eating impellers around here (Ortega FL).
    Folk talk about impellers lasting two years or near a thousand hours. One year or 250 hours around here.

Share This Page