Announcement

Collapse
No announcement yet.

Raw water pump idler pulley bearing failure-gctid813218

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Raw water pump idler pulley bearing failure-gctid813218

    This happened to me a couple weeks back now, but I've only just now had a chance to post about it. It's a long post, so you can just read the TLR if you want

    TLR - My raw water pump idler pulley bearing failed, it was a cheap and easy fix... but I am wondering about belt tension on that belt. Service manual says you should be able to depress the belt 1/4" when properly tensioned... but how much force should it take to do that.... just a light touch with a finger? Paranoid about putting too much force on the raw water pump pulley, but that pump turns fairly hard (ie. I can turn it by hand ... but it's not easy) so without a reasonably tight belt it slips and squeals a bit.

    The full story:

    The family and I were out on our first proper outing of the season second last weekend in May. Had a beautiful time, cruised down to Orcas Island from Point Roberts on the Saturday morning, spent some time walking around Obstruction Pass state park, then anchored overnight at Lieber Haven Marina Resort. Next morning headed up to Rosario, stopping off at Olga on the way. Had another nice night at the Rosario marina, met up with my sister who came up from Edmonds for the day. Set off late Monday morning to make our way home. Boat was purring like a kitten the entire trip...

    ....until....

    Just as we were turning to head into Obstruction Pass, maybe 15-20 minutes into our trip home.... I suddenly hear this loud buzzing... it was so loud I looked up and behind me expecting a seaplane was flying low above me.... but just as I did that, the engine just dies... no hesitation, just 3800 RPM to zero in a few seconds. I open the engine compartment, it's HOT... smells bad like something burning... and I'm thinking the worst... somehow it's seized or something. Like others I'm sure, I am pretty vigilant about constantly scanning my engine temp and oil pressure gauges.... just habit from growing up on a farm and operating heavy machinery much of my life... drilled into me by my Dad from a young age. So I knew that within the past 5 minutes or so of this happening, I had normal engine temp and oil pressure. But now.... engine is very hot... gauge is reading in the mid-200's. We're drifting with the current ... we were in around 80 ft of water but rapidly getting deeper as we drifted out into the main channel of the pass... so I dropped my anchor and got myself hooked.

    Turned the engine over a few times... it turns over, so not seized.... but won't run. I take a closer look around the engine compartment... and spot this. The belt wasn't actually off, which is why I hadn't immediately noticed it, I pulled the belt off afterwards:



    Here is whats left of that idler pulley.... bearing seized and the heat melted the plastic pulley.



    So... looks like that bearing got nice and hot... melted the pulley off, stopping the raw water pump, the engine overheats very quickly but since the fuel pump is attached to the raw water pump the engine can't keep running (I always wondered about that design decision, but it sure makes sense to me now ) It's actually something I could have fixed on the water... but who carries a spare like that? I even had a spare belt for it... but no pulley. So... TowBoatUS to the rescue. We were very fortunate, there was a boat with a captain on it immediately ready to go from Friday Harbour and they were with us within 45 minutes. Unfortunately, it took 6 1/2 hours to get back to Point Roberts due to adverse currents... we could barely make 4 kts.... but I'm just happy we were 100% covered as the invoice was just over $1700 :blink:

    So I replaced the pulley and belt, and things are good again... entire fix was under $50, but I'm wondering a couple things:

    [ol]

    [li]How easy (or hard) should that raw water pump turn by hand? It takes some effort to turn it, not sure if this is normal.[/li]

    [li]The service manual says one should be able to depress the properly tightened belt approximately 1/4" ... but again, not sure how much force one should be applying to achieve this. Without this belt reasonably tight it squeals due to point 1 above,[/li]

    [/ol]
    Tyson, Ackerley, Sidney & Gene
    Tsawwassen, BC
    1996 2858 Ciera Command Bridge
    Mercruiser 7.4L BRAVO II (GEN. V) GM 454 V-8; Engine Serial 0F603347
    "Island Passport"
    Home marina: Point Roberts, WA

    #2
    There is going the be some resistance turning the water pump without water in it. With water in it it cane be a bit tougher. If you can't get a wiggle out of the pulley, and it's not dripping, you are 99 percent good to go. As to the quarter inch, it should take a significant amount of pressure with your fingers on the longest section between pulleys to get that quarter inch. Just like on your car. If the belt squeals on acceleration, it's too loose.
    P/C Pete
    Edmonds Yacht Club (Commodore 1993)
    1988 3818 "GLAUBEN”
    Hino EH700 175 Onan MDKD Genset
    MMSI 367770440

    Comment


      #3
      Had one of those fail once off the west coast of Vancouver Island in Bamfield. I went into the small local shop and he had just ordered 2 spares. Told me they are a very common point of failure.

      I'd simply tension the belt to the recommended spec and go boating. I think you should be fine now that the part has been replaced.
      Terry
      1999 Bayliner 3388
      Twin Cummins 4BTA
      Fisherman, Cruiser, Boaticus-enthusiasticus-maximus
      Member Royal Victoria Yacht Club

      Comment


        #4
        "TenMile" post=813225 wrote:
        Had one of those fail once off the west coast of Vancouver Island in Bamfield. I went into the small local shop and he had just ordered 2 spares. Told me they are a very common point of failure.

        I'd simply tension the belt to the recommended spec and go boating. I think you should be fine now that the part has been replaced.
        Yeah, I'm going to order a spare to carry anyway... but since it's just been replaced I'll probably never need it.
        Tyson, Ackerley, Sidney & Gene
        Tsawwassen, BC
        1996 2858 Ciera Command Bridge
        Mercruiser 7.4L BRAVO II (GEN. V) GM 454 V-8; Engine Serial 0F603347
        "Island Passport"
        Home marina: Point Roberts, WA

        Comment


          #5
          Not sure if you have checked the lube oil in the raw water pump bearing housing or not but that does need to be looked at also. When I looked at mine there was almost no oil in it and what was left looked like mud. The bearings were not in great shape when I took it completely apart.

          You can buy a kit to rebuild this center section of the pump.
          Doug
          1995 2859 -extensively rebuilt/restored 2016/17
          496 big block - Bravo ll leg
          The Doghouse
          Prince George BC

          Comment


            #6
            "sketch96" post=813248 wrote:
            Not sure if you have checked the lube oil in the raw water pump bearing housing or not but that does need to be looked at also. When I looked at mine there was almost no oil in it and what was left looked like mud. The bearings were not in great shape when I took it completely apart.

            You can buy a kit to rebuild this center section of the pump.
            Are you referring to the oil in the housing under the fuel pump? I replaced that gear oil a few months back when my fuel pump failed (thankfully, it happened at the dock!). It was right full of very gasoline thinned oil.... I absorbed it out with paper towels, and refilled with fresh oil.

            EDIT: If the answer to the above IS yes... as a follow up... how often should that oil be checked/changed? And also... is rebuilding in the absence of an obvious issue something that should be done as preventative maintenance? I did check into prices for a new pump as I was replacing that idler pulley, since I thought it was turning too hard... but a new pump is a lot more than I thought... but the rebuild kits seem reasonable.
            Tyson, Ackerley, Sidney & Gene
            Tsawwassen, BC
            1996 2858 Ciera Command Bridge
            Mercruiser 7.4L BRAVO II (GEN. V) GM 454 V-8; Engine Serial 0F603347
            "Island Passport"
            Home marina: Point Roberts, WA

            Comment


              #7
              I would think it should be done as preventive maintenance especially if your not sure of the hours on it or if it has ever been done before. I did the one I have for those reasons. I also replaced the idler pulley/bearing for the same reason. Piece of mind. Nothing worse than wasting some good time off with a breakdown.

              And I did the same thing as you......i looked at the price of a whole new pump and decided rebuilding was much cheaper. I replaced the impeller and housing plus a new fuel pump while the whole assembly was off on the bench. So much easier.
              Doug
              1995 2859 -extensively rebuilt/restored 2016/17
              496 big block - Bravo ll leg
              The Doghouse
              Prince George BC

              Comment


                #8
                My opinion: piss poor design. I've gone through two already. Next time, I think I'll go with the main engine pulley design that I've read about on the BOC site.
                Simo
                2002 2855 350MPI Bravo III on Lake Champlain -> SOLD!
                Downsized to a couple of kayaks for now.

                Comment


                  #9
                  "simo" post=813620 wrote:
                  My opinion: piss poor design. I've gone through two already. Next time, I think I'll go with the main engine pulley design that I've read about on the BOC site.
                  2 what? Raw water pumps?
                  Tyson, Ackerley, Sidney & Gene
                  Tsawwassen, BC
                  1996 2858 Ciera Command Bridge
                  Mercruiser 7.4L BRAVO II (GEN. V) GM 454 V-8; Engine Serial 0F603347
                  "Island Passport"
                  Home marina: Point Roberts, WA

                  Comment


                    #10
                    I do like the idea of a crank driven raw water pump and an oil pressure triggered electric fuel pump. Get rid of the hard to access water pump/ fuel pump, belt and idler pulley.. .........its on my future to do list down the road.
                    Doug
                    1995 2859 -extensively rebuilt/restored 2016/17
                    496 big block - Bravo ll leg
                    The Doghouse
                    Prince George BC

                    Comment

                    Working...
                    X