Water pump |
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73SN ![]() Senior Member ![]() ![]() Joined: October-05-2005 Location: United States Status: Offline Points: 147 |
![]() ![]() ![]() ![]() ![]() Posted: July-11-2011 at 8:07pm |
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This may be a dumb question but I gotta ask it:
I have a '73 Ski Nautique with a 351 that overheated this weekend. Does the water pump on the front of the engine function or is it just a cover and receptacle? It has a pulley but I'm just wondering why have two: impeller and regular pump. |
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8122pbrainard ![]() Grand Poobah ![]() ![]() Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Paul,
Yes, both pumps have a definite purpose. The RWP (raw water pump) that's been added onto the marinization is a semi positive displacement pump that's needed to lift (suction head) the water up to the engine. The OEM centrifugal pump will not do that. The OEM circulation pump is simply there to circulate water though the block as needed depending on how open the T stat is. So, tell us more about your overheat. You haven't been running the engine without water have you? BIG time BAD!!! |
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73SN ![]() Senior Member ![]() ![]() Joined: October-05-2005 Location: United States Status: Offline Points: 147 |
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Oh no, I know better than that. Thanks, I suspected as much on the two pumps but wasn't sure after getting it off and looking at it, especially as loosely as it turned. I haven't had any problems and we've been on the water 4 or 5 times over the last couple of months. We were headed up river on Saturday, I'd say about 25-30 minutes into the trip north doing about 35 mph and I heard a high pitched noise gradually get louder. The water temp indicator read about 150 which was unusual so I eased off and kept it at about idle speed but sped back up for a bit so I could look out the back to see if water was flowing and its was, not sure it was enough though. I raised the engine cover and had my wife cut the engine. I saw a puff of smoke from the oil cap which really scared me. I could tell it was hot. I just got back from the marina and they'll have to send it off for rebuild. They tell me I'm down for a week. I hope it doesn't end up being the RWP when its all said and done. It is 38 years old after all and may need rebuild just for good measure. I try to keep on top of things but didn't see this coming. |
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Luchog ![]() Grand Poobah ![]() ![]() Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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how hot did it get?
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73SN ![]() Senior Member ![]() ![]() Joined: October-05-2005 Location: United States Status: Offline Points: 147 |
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All I have is a water temp gauge. The highest I saw was 160 after I shut 'er down. I've never seen it much more than 100.
I don't know exactly where that is measured but I figured it would rise after shut down with no water running thru the engine. The radiating heat was more than I've felt before so I know it wasn't normal. |
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73SN ![]() Senior Member ![]() ![]() Joined: October-05-2005 Location: United States Status: Offline Points: 147 |
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Also, I just reread above and didn't realize it had a thermostat. How does that work? I can understand a car because the water is contained in the block and warms to open it.
Anyway, I'm pretty sure its a pump problem. |
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Luchog ![]() Grand Poobah ![]() ![]() Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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If you never saw more than 100 I'd dare saying you are running without a thermostat, 160 wont damage the engine.
This is all considering the gauge/sender are good. |
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Greasy Lake ![]() Newbie ![]() ![]() Joined: May-27-2009 Status: Offline Points: 16 |
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Hypothetically, what would be so wrong about running our boats without a thermostat?
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8122pbrainard ![]() Grand Poobah ![]() ![]() Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Not given, The marine engine industry learned way back in the 40's that engine temps need to be controlled to maintain efficiency as well as oil viscosity. If you need to run without a T stat, you have a problem that needs addressing. |
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8122pbrainard ![]() Grand Poobah ![]() ![]() Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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73SN ![]() Senior Member ![]() ![]() Joined: October-05-2005 Location: United States Status: Offline Points: 147 |
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Any tips before I get started on the water pump?
Not sure what the extra screws are for: http://s1211.photobucket.com/albums/cc430/house777/Boat%20Pics/ |
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Luchog ![]() Grand Poobah ![]() ![]() Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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not that water pump!!!!!
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8122pbrainard ![]() Grand Poobah ![]() ![]() Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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It sure would be nice if we new knew if you are concerned about your RWP or the circ pump!! Your attempt at trying to provide a link flunked BIG time!!! What extra screws? |
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Gary S ![]() Grand Poobah ![]() ![]() Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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I hope it's not that pump you took to the marina.The only things that go wrong with them is either they leak out the weep holes or get noisy. Some older marine engines don't even have those pumps,they rely only on the raw water pump.
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Keeganino ![]() Grand Poobah ![]() ![]() Joined: October-27-2009 Location: North Carolina Status: Offline Points: 2063 |
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Pete the images showed up for me... pics
The 2 screws hold the backing plate on the water pump. They go side by side on the top I think. Make sure that your mating surfaces are very clean. Had to redo mine since the gasket was leaking like a sieve. I also broke a bolt over torquing it and had to start all over. |
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"working on these old boats may not be cost effective but as it shows its what it brings into your life that matters" -Roger
1973 Skier |
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BuffaloBFN ![]() Grand Poobah ![]() ![]() Joined: June-24-2007 Location: Gainesville,GA Status: Offline Points: 6094 |
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What rotation is that circ pump?
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DrCC ![]() Grand Poobah ![]() ![]() Joined: April-12-2004 Location: at home Status: Offline Points: 2867 |
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Green plastic pump? Maybe painted red?
Look inside! Maybe Toast! |
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73SN ![]() Senior Member ![]() ![]() Joined: October-05-2005 Location: United States Status: Offline Points: 147 |
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Thanks all,
Sorry if the pic link didn't work I tried a few different ways and it worked for me with highlight and right click on "go to ...." I'm replacing the circulation pump first. I'm not positive thats the problem and it may end up being the RWP. I'm guessing by the high pitch sound location and the water flow rate that its not the RWP. I'll deal with it next if this doesn't cure it. They told me they couldn't match it and they'd have to send it off for rebuild. 2 weeks later they told me they had it and I get there and its not the same pump... It has two extra holes closer to the shaft and two small stainless screws with it. After closer inspection I'm sure they're useless. They dont hold the plate on. |
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73SN ![]() Senior Member ![]() ![]() Joined: October-05-2005 Location: United States Status: Offline Points: 147 |
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That was my original concern about having a RWP only. Wish I'd have popped open the old pump before I dropped it off. I was trying to rush and get the kids wakeboarding before summer vacation is over. |
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73SN ![]() Senior Member ![]() ![]() Joined: October-05-2005 Location: United States Status: Offline Points: 147 |
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Marina Mechanic explained: The water circulates without flowing thru the exhaust until the thermostat opens. it flows higher in the engine and water manifold and then thru the exhaust as the thermostat opens. Mine is probably stuck open. That part looks original and untouched. (Assuming I'm looking in the right spot) |
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Gary S ![]() Grand Poobah ![]() ![]() Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Better change marina's fast. Water always flows thru the exahust,otherwise the rubber or in some cases fiberglass,would get hot and burn thru leaving you at the bottom of the lake
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8122pbrainard ![]() Grand Poobah ![]() ![]() Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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I agree and unless you misunderstood the mechanic, he had better go back to school!! Water flows through the engine as needed controled by the T stat and always through the exhaust manifolds. |
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DrCC ![]() Grand Poobah ![]() ![]() Joined: April-12-2004 Location: at home Status: Offline Points: 2867 |
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And, next time you talk with your Marine mechanic, make sure you ask him if he once worked at Sears Automotive Center.
Water by-passes to cool exhaust, so that it doesn't turn a '73 SN into a pretty habitat for fish. |
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Keep it....from sinkin'
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73SN ![]() Senior Member ![]() ![]() Joined: October-05-2005 Location: United States Status: Offline Points: 147 |
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I'm bad about misunderstanding folks. I'm sure he meant it didnt flow from engine block thru the exhaust. He never said it didnt flow when it wasn't open. He didnt have time to fully explain it and I made some ASSumptions. Thanks all for straightening that out.
I went back today to pick up a new bilge pump and took another look at the old circulation pump. (they still had it) once again I misunderstood: the two screws do hold on the plate. I had the gaskets swapped and was confused about the relation to the extra holes in the new pump. I'll try not to rush thru things before I post next time. |
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Gary S ![]() Grand Poobah ![]() ![]() Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Thats ok Paul,you don't learn anything if you don't ask.We just don't want to see anyone taken advantage of.
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8122pbrainard ![]() Grand Poobah ![]() ![]() Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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You're cool!!! Now you know!! ![]() |
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73SN ![]() Senior Member ![]() ![]() Joined: October-05-2005 Location: United States Status: Offline Points: 147 |
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I've learned a good bit taking this beast apart... hate to look back at old posts now
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cphase ![]() Gold Member ![]() ![]() Joined: May-11-2010 Location: Newnan, GA Status: Offline Points: 795 |
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This may be the impeller you are looking for.
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73SN ![]() Senior Member ![]() ![]() Joined: October-05-2005 Location: United States Status: Offline Points: 147 |
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73SN ![]() Senior Member ![]() ![]() Joined: October-05-2005 Location: United States Status: Offline Points: 147 |
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Thanks Jeff. Its a bit different on the shaft, (no key)
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