OMC Water Pump

Discussion in 'Sterndrives' started by XtinctEngr, May 25, 2014.

  1. XtinctEngr
    Joined: May 2014
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    XtinctEngr Junior Member

    How long do these water pump impellers last? Fresh water use only.

    The reason I am asking, I am restoring a '81 Celebrity that has an OMC 800 Sea Drive (Model 982461, 1980 model) and it has been sitting many years in dry storage.

    However, at some point in it's illustrious past a different lower unit was mounted. I found this out when trying to remove the peeling paint applied by the PO.

    [​IMG]

    I have ordered a manual, but with this different lower unit, gaskets, seals,etc may prove interesting. Is there a way I can find out what year/model lower unit this is?
     
  2. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Impellers last approx. 1 minute when run dry, several seasons when properly used.
    Manufacturers advise to change the impeller every year but I know nobody who really does that. Your restoration project certainly needs a new one after sitting dry for a long time.
     
  3. XtinctEngr
    Joined: May 2014
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    XtinctEngr Junior Member

    Oh Yeah, I agree. Here's hoping that along with a new water pump and impeller, a gasket/seal set will be all that is needed. My real concern is with the lower unit since it was added and under closer examination doesn't quite fit right - see poor photo:

    [​IMG]

    Should I consider replacement? It did work well before the long dry spell.

    It is not going back into the water until I am confident everything is okay.
     
  4. CDK
    Joined: Aug 2007
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    CDK retired engineer

    I think it is the upper part you should worry about!
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Impellers are consider a consumable part, just like an oil filter. Toss any you might have doubt about, regardless of age or use. That drive leg looks pretty bent and those old OMC's aren't known for their good behavior. This looks like a bag of worms, if you haven't any experience with I/O's in general and old OMC's in particular.
     
  6. XtinctEngr
    Joined: May 2014
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    XtinctEngr Junior Member

    "That drive leg looks pretty bent"

    I think that is because of the angle of the pic. The lower unit matches perfectly of the right-side of the housing but comes a bit short on the left - just not a "smooth match" on both sides. As I mentioned earlier, it worked well before the dry spell.
    Granted, this is not the best case scenario, but it IS the cards I have been dealt and I need to address the issue. A "proper-fitting/operating" lower unit can cost anywhere from $1 -> 2K and I just don't have that kind of bank account (retired).
    And, yes, I have no experience with these sea drives, but as an old mechanical engineer, I feel very confident that I can handle most everything I run across especially with the help and experience of this forum.
    I did have another thought and maybe someone could guide me. Since this lower unit has performed well in the past, is it possible to move the internals to a different (proper fitting) case as those are somewhat more affordable. Or is this a pipe dream?
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    They stopped making those drives in the early 80's, so finding a suitable donor will be difficult, at least one that's serviceable anyway. I'd be inclined to find a $500 donor boat, with a whole different drive, possible the same engine, so some part interchangeability is available. 20 year old Bayliners abound around here and I suspect up there as well, with forlorn owners, looking to free up their carport. They usually just need basic maintenance, some upgrades and consumable parts, to get beck in reasonable condition. Your call, work with 30 and 40 year old parts, that where never perpendicularly well regarded, that are hard to find and well worn out or . . .
     
  8. XtinctEngr
    Joined: May 2014
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    XtinctEngr Junior Member

    I agree Par, finding a donor boat would be the best...uh...most economical thing at this point and I have been looking around. The 305 Chevy (I think that is what I have) is in pretty good shape, not froze up, no water in the oil- it was a little sludgy when I drained it out - but I wasn't too surprised by that. I have removed the carb for rebuilding just after this photo was taken.

    [​IMG]

    As far as a donor boat goes, can anyone tell me the difference to the sea drives for say a 175Hp, 200 Hp (this one) and the 260Hp? Would they all match up at the ball gear (which I probably would need to change anyway) as far as alignment?
     
  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Each drive will have different bell housing and transom cutout requirements, but they'll all bolt up to a small block, with little difficulty, assuming the right parts.

    Finding a donor boat, possibly with a blown engine, but good drive will take some leg work, but I run across several each year and I'm usually not looking for them. An ideal donor will also have a Chevy small block, so the parts directly transfer. If it's a Ford or other engine, you can still do it, except you'll be looking for odd bits and pieces to make things work. The Chevy small block is about as popular a setup as you can find, so look around.

    A two barrel, 305 (what you have) will usually produce 200 HP, with a 4 barrel 225 and is usually married to a Mercrusier Alpha. The 350 is usually more HP, up to about 260 and more commonly tied to a Bravo drive, though I've seen Alphas too.

    Log onto ebasicpower.com to look up parts and familiarize yourself with the drive differences.
     

  10. XtinctEngr
    Joined: May 2014
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    XtinctEngr Junior Member

    Thanks Par for the link. I am just OCD enough to spend a lot of time familiarizing myself before a take anything totally apart. I have succumbed to the fact that this restoration will be a long process.
     
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