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Raw Water Pump Problem?-gctid386256

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    Raw Water Pump Problem?-gctid386256

    I recently purchased a 1988 Bayliner 2556 with a 5.7 OMC inboard/outboard. This is my first boat. When checking it out ahead of time, we ran it with a hose/muffs on the outdrive. Seemed to work fine. When my son and I took it to the docks to launch it though, it started getting hot after only about 5-10 minutes of use. It is currently sitting at the docks, and I have not been running it. A friend of mine recommended a boat mechanic, and he went down to take a look at it. His response was "you need new exhaust manifolds, they are rusted out." I've done quite a bit of reading on various forums about the cooling systems and have done what I can to learn about my cooling system. I am very familiar with working on cars, but like I said, this is my first boat. I have an OMC manual and read through that a lot before heading down to my boat this past weekend. The plan was to pull the exhaust manifolds, have them checked, and possibly replace them.

    Went to the boat this weekend and my cooling system is a bit different than what was in my manual. The raw water hose from the outdrive comes up to a small cooler (for power steering fluid), then a hose runs to a heat exchanger near the front of the engine, rather than to the thermostat housing as shown in my manual. The raw water runs through the heat exchanger, exits a hose that T's off and goes up to the exhaust manifolds. The water then runs through the exhaust manifolds and exits the engine.

    Out of the thermostat housing, a radiator hose runs up to a canister (what I would call like an overflow tank on a car), another radiator hose runs down to the heat exchanger, and is cooled by the raw water. Another radiator hose runs out of the heat exchanger to the engine block. In a nutshell, that's my cooling system.

    So I wanted to verify things and make sure there were no other "clogs" in the system. I pulled the hose that runs from the power steering cooler to the heat exchanger, and started the motor, just to make sure raw was flowing nicely at that point. Plan was to dump it into a 5 gallon bucket. NOTHING!!! No raw water being pumped in. So I went backwards in the system, and pulled the hose off right at the tube where it comes into the engine compartment/hull, which I assume the raw water pump is right on the other side. With the engine running, there is no water flowing at this point.

    So am I correct to assume the water pump is bad and/or the pickup screen is clogged? Seems like an excellent place to start.

    What I did next was a little odd, but think it gave me hope the remainder of the cooling system (including those manifolds) is ok. I have a washdown hose on the boat that pumps seawater directly up from the bottom of the boat. I took that hose (pretty much a garden hose) and hooked it up to the heat exchanger, ran the motor, and turned on the hose. Essentially, I was pumping sea water into my system via a different route. I read on here (today) in another thread that the water pump should run with the motor RPM's, so I hope I didn't do any damage. But, I ran it for about 10 minutes, motor stayed plenty cool, I watched the temp gauge go up, then down, as it should with the opening/closing of the thermostat. The exhaust caps stayed cool enough I could touch them. I still want to pull my exhaust at some point and have it all checked, but this gave me hope that it is not the emergency the "mechanic" :thumb told me I had.

    Am I thinking right about this here? Replace raw water pump in the outdrive and I should be good to go? I don't think it is possible to replace it while it is in the water since I have a swim step there.

    Also, I noticed when poking around the outdrive that the bottom bolt holding the cover on is missing. Thus, I am sure water has flowed into this upper area of the outdrive. There does not appear to be a gasket/seal on this cover anyway, so I am assuming water getting in that area is ok? If not, well .... ugghhh.

    Any thoughts and comments here would be appreciated. The wife is not too happy we have a "new boat" that we can't run yet. Thanks so much for any assistance.

    #2
    Sorry the post above was so long, but hopefully someone can give me some answers? Thanks in advance.

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      #3
      Tilt your drive up and remove the plastic cover on the back of it. The raw water pump is right there, so you should be able to pull it apart while in the water and check the impeller. If you have to replace it, do it as an entire kit-housing, metal sleeve, impeller, gasket(s). Resist the temptation to just put a new impeller in there if it is cooked. It WILL NOT WORK PROPERLY! I'm surprised you didn't get water running into the boat when you took off the hose on the transom assy though because that is under water. Pop the impeller out first and see what's up there....

      Comment


        #4
        mainecoast wrote:
        Tilt your drive up and remove the plastic cover on the back of it. The raw water pump is right there, so you should be able to pull it apart while in the water and check the impeller. If you have to replace it, do it as an entire kit-housing, metal sleeve, impeller, gasket(s). Resist the temptation to just put a new impeller in there if it is cooked. It WILL NOT WORK PROPERLY! I'm surprised you didn't get water running into the boat when you took off the hose on the transom assy though because that is under water. Pop the impeller out first and see what's up there....
        THanks for the response. There was water in the tube at the transom, up to the top of it. It just was not "pumping" water like it should be.

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