After traveling for 9 hours over a 2 day period from the hudson river to the long island sound just as I picked up my mooring at the end of the trip my engine overheated. How Do I check if I sucked in a plastic bag or my impeller went bad. Is the impeller located by the seacocok. Excuse the stupid questions as I just got the boat and am not too mechanical? Thanks for your help. Richard (Duke)
Engine Overheat HUnter 1999 3gm30f
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Could be a number of things
If the engine was fine until the very end, you may have caught debris in the raw water intake. Turn the yellow lever down and dismantle the hose at the seacock. When you turn up the lever, water should be rise up in a constant stream that will quickly inspire you to close the seacock and reassemble, since that's not the problem. If it is the problem, poke a bended coathanger down the seacock to dislodge the implement. Good call on the impeller, since its destruction would lead to overheating. Dismantle the water pump, which may require dismantling the fan belt lower unit which has two lag bolts.
If the engine was fine until the very end, you may have caught debris in the raw water intake. Turn the yellow lever down and dismantle the hose at the seacock. When you turn up the lever, water should be rise up in a constant stream that will quickly inspire you to close the seacock and reassemble, since that's not the problem. If it is the problem, poke a bended coathanger down the seacock to dislodge the implement. Good call on the impeller, since its destruction would lead to overheating. Dismantle the water pump, which may require dismantling the fan belt lower unit which has two lag bolts.
Check
...for water flow at the exhaust port on the hull when the engine is running. This is very quick and easy to do. One look will confirm water flow or not. There is a sea water strainer in the engine compartment which has a screen in it. The housing is see thru so you can see if it is clogged with debris. If there is no clog the impeller is the most likely suspect. Removing the back plate on the pump takes just a couple of minutes. If any of the arms of the impeller are missing or broken you have found the culprit. Always carry a spare impeller onboard, it can be the difference between getting home or not. Becoming familiar with replacement of the impeller is something that every boater owner should know.
...for water flow at the exhaust port on the hull when the engine is running. This is very quick and easy to do. One look will confirm water flow or not. There is a sea water strainer in the engine compartment which has a screen in it. The housing is see thru so you can see if it is clogged with debris. If there is no clog the impeller is the most likely suspect. Removing the back plate on the pump takes just a couple of minutes. If any of the arms of the impeller are missing or broken you have found the culprit. Always carry a spare impeller onboard, it can be the difference between getting home or not. Becoming familiar with replacement of the impeller is something that every boater owner should know.
Overheating?
My first thought would be to check the impller which is located in an awkward position on older Yanmar engines. I have the same engine so I speak from some experience. First: Close the raw water intake seacock and then loosen the pump maounting bracket bolts so that you can get the pump belt off. Second: Remove the whole pump assembly from the engine by taking out the bolts you just loosened. Finally: Remove the intake hose from the pump assembly. Now you have the pump/bracket in your hands and you can see the impeller cover on the back side of the pump housing. Remove the small screws which hold the cover on and inspect the impeller. If it looks bad (missing or cracked vanes) replace the impeller and the gasket and you have probably solved your problem. Even if it looks OK, I would replace it if I did not know how old it was and keep it as an emergency spare. If the impeller looks OK then you may have a clogged intake. I have never cleared one of these but this is what I have been told would work. Remove the hose from the raw water seacock with it closed. Replace it with a length of equal diameter hose which is long enough to reach well above the waterline. Open the raw water seacock and backflush with pressurized water or air - not sure how you would do this on a mooring because I am on a dock. Finally, since you did not mention it, I assume that your engine had sufficient antifreeze on the fresh water side and that you had good water flow out of the exhaust. Antifreeze leaks are not uncommon and clogged mixing elbows on a nine year old engine are not unexpected.
My first thought would be to check the impller which is located in an awkward position on older Yanmar engines. I have the same engine so I speak from some experience. First: Close the raw water intake seacock and then loosen the pump maounting bracket bolts so that you can get the pump belt off. Second: Remove the whole pump assembly from the engine by taking out the bolts you just loosened. Finally: Remove the intake hose from the pump assembly. Now you have the pump/bracket in your hands and you can see the impeller cover on the back side of the pump housing. Remove the small screws which hold the cover on and inspect the impeller. If it looks bad (missing or cracked vanes) replace the impeller and the gasket and you have probably solved your problem. Even if it looks OK, I would replace it if I did not know how old it was and keep it as an emergency spare. If the impeller looks OK then you may have a clogged intake. I have never cleared one of these but this is what I have been told would work. Remove the hose from the raw water seacock with it closed. Replace it with a length of equal diameter hose which is long enough to reach well above the waterline. Open the raw water seacock and backflush with pressurized water or air - not sure how you would do this on a mooring because I am on a dock. Finally, since you did not mention it, I assume that your engine had sufficient antifreeze on the fresh water side and that you had good water flow out of the exhaust. Antifreeze leaks are not uncommon and clogged mixing elbows on a nine year old engine are not unexpected.
Broken impeller caution
If you find that there are vanes missing from the impeller you have to ask where those little parts went. They generally get stuck in the heat exchanger manifold. This is not too difficult to check as the manifold is easy to get at. if memory serves you don't even have to drain the engine anti to check it. follow the hose from the raw water pump up to where it enters the engine, that is the manifold. Take off the bolts and gently pull off the "cover" to see if the vanes are stuck there.
If you find that there are vanes missing from the impeller you have to ask where those little parts went. They generally get stuck in the heat exchanger manifold. This is not too difficult to check as the manifold is easy to get at. if memory serves you don't even have to drain the engine anti to check it. follow the hose from the raw water pump up to where it enters the engine, that is the manifold. Take off the bolts and gently pull off the "cover" to see if the vanes are stuck there.
Broken Impeller caution 2
Bill R is right to tell you to check your heat exchanger for the broken or missing impeller vanes. If you are lucky the vanes will be stuck in the raw water inlet to the heat exchanger and you can just pull the hose where it enters the exchanger and grasp the broken vanes with a tweezers. If you can't see them, then pull the cover to the exchanger and expand your search. Happy Hunting!
Bill R is right to tell you to check your heat exchanger for the broken or missing impeller vanes. If you are lucky the vanes will be stuck in the raw water inlet to the heat exchanger and you can just pull the hose where it enters the exchanger and grasp the broken vanes with a tweezers. If you can't see them, then pull the cover to the exchanger and expand your search. Happy Hunting!
Similar problem on my 3GM30F
I have similar problem on mine but I was just running mine at the dock to keep things running... noticed no water was coming out and made sure the seacock was open, still nothing. it just happened to be I noticed a leak in my raw water pump and having that replaced, I thought I might as well take it home and noticed that the impeller was missing 2 blades. one fell out of the host on the "out" side of the pump but I expect the second is somewhere around the heat exchange. What worked for you Duke ? is there anything I need to be aware of when opening the cover to look at the heat exchanger ?
I have similar problem on mine but I was just running mine at the dock to keep things running... noticed no water was coming out and made sure the seacock was open, still nothing. it just happened to be I noticed a leak in my raw water pump and having that replaced, I thought I might as well take it home and noticed that the impeller was missing 2 blades. one fell out of the host on the "out" side of the pump but I expect the second is somewhere around the heat exchange. What worked for you Duke ? is there anything I need to be aware of when opening the cover to look at the heat exchanger ?
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