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RWP not sucking- overheating- 1999 GT 40 5.8 |
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Skifunseeker01 
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Joined: July-27-2011 Status: Offline Points: 19 |
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 Topic: RWP not sucking- overheating- 1999 GT 40 5.8Posted: August-12-2022 at 3:21pm |
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I changed by impeller, like I have every year. Since I changed it the RWP isn't drawing water- I checked with a bucket. I have checked the water lines, cleaned the screen and cup in the strainer. I am positive I installed the RWP correctly- the Serial number starts with PLP so the screw should be orientated towards the block. I have replaced the thermostat as well- it did have some old gasket or rubber on the smaller free flowing hole but I cleaned that out. Any thoughts? Circulation pump? Just trying not to go on a part swapping fest if someone has a better solution.
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desertskier
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Joined: December-19-2006 Location: Az Status: Offline Points: 1115 |
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Posted: August-12-2022 at 3:30pm |
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Check the bond between the metal hub and the rubber impeller body. I had one recently that looked fine but the hub was spinning and not the body.
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92 SN - Owned since 93
99 Pro Air 89 SN - Went to live on a lake in Texas 75 Donzi 16 - Sold in 93 |
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desertskier
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Joined: December-19-2006 Location: Az Status: Offline Points: 1115 |
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Posted: August-12-2022 at 3:32pm |
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Also, make sure the metal key is installed.
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92 SN - Owned since 93
99 Pro Air 89 SN - Went to live on a lake in Texas 75 Donzi 16 - Sold in 93 |
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Skifunseeker01
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Posted: August-12-2022 at 9:16pm |
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Thanks- I'll check on the hub but the pump feels correct when I free spin it. I was just wondering if some else could be blocked from the strainer to the pump.
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desertskier
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Posted: August-12-2022 at 9:44pm |
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If you have a strainer check that the gasket is installed correctly. I don't remember if my '99 has a strainer or not. I guess I would have to put down my beer and go outside and check.
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92 SN - Owned since 93
99 Pro Air 89 SN - Went to live on a lake in Texas 75 Donzi 16 - Sold in 93 |
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PLBC
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Joined: January-25-2006 Location: United States Status: Offline Points: 568 |
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Posted: August-12-2022 at 11:58pm |
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Sucking air somewhere. Triple check connections and gaskets
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3750 |
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Posted: August-13-2022 at 2:16am |
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I will offer another possible issue. I did this myself so I know it is easy to do.
The Water Pump can be installed 180* off. One way you have perfect suction and water delivery. Turn it the other way and you get ZERO water intake. It overheats very quick. There is a Screw on the side of the pump, I think it hods in the Cam plate inside, it has been reported on here many times but the plug either faces your engine or it faces away from the engine block depending on standard rotation or reverse rotation. A 1999 GT40 with a 1.23:1 Transmission is a standard rotation engine. My mind must be going because it has only been about 3 years since I did this mistake and I need to look up the orientation. Trust me, the pump looks the same and hooks up the same in both installations. The good news is you can flip it back over and be done in about 10 minutes. Edit: Can't believe I had to go look this up after the trouble it caused me but here you go: 1.23 gear boxes use a Left Hand Standard Rotation Engine with a Right Hand Prop This combo has the Screw on the Raw Water Pump facing IN towards the Engine Block. The Older Boats with a Right Hand or Reverse Rotation engine the Raw Water Pump Screw needs to face Out away from the engine block.
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gun-driver
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Posted: August-13-2022 at 5:47am |
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when you said you checked with a bucket where was the hose attached, bottom of the pump?
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KENO
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Posted: August-13-2022 at 7:01am |
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Since most people who do the yearly impeller change do it at the beginning of the season, were you changing the impeller mid season because everything was just fine and you felt like changing it or were you having cooling issues and decided to change it?
Since you asked in earlier posts, the thermostat or the circulating pump have no effect on the raw water pump's ability to draw water and the transmission oil cooler is after the strainer in the pump suction path on your boat If everything was good before you took it apart, I'd take it apart again and check things out. You do it every year, you're probably good at it.  Paper gasket and O ring both in place ?
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Skifunseeker01
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Posted: August-13-2022 at 8:53am |
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Thanks for the advice- I'll go and recheck everything again. Maybe a loose hose clamp or something causing a leak. I did the change the impeller because the boat was heating up after a set. It would cool back down when running but it never used to do this- it always ran at 160 then bump to 190 after sitting. We have had a lot of weeds floating around due to the extreme hot weather so I thought it might have sucked something up. Our lake is under assault from Hydrilla.
For Keno- yes to the paper gasket and O ring. I'm guessing that it would be rare for the tranny cooler could get blocked. Should I remove it and look for obstructions if no joy after looking over all the intake hoses. I'll give a follow up after I spend my day searching this out.
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JDD33
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Joined: October-20-2012 Location: Natick, MA Status: Offline Points: 499 |
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Posted: August-13-2022 at 9:48am |
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Sound similar to a problem I was having earlier this year on my ‘85 BFN. Changed the impeller in the spring and she ran well for about a month then started having issues with the temp creeping up and finally it wasn’t cooling or sucking any water. Checked everything including another new impeller and some intake hose that we thought might be collapsing.
Does the back of your pump body get hot when the engine is running on the bucket? If you remove the belt and move the pulley and shaft of the pump does the main shaft move side to side in the area where the bearings are? The final conclusion to my over heating issue was that the bearings in my pump are wearing out and need to be replaced. With TOO MUCH belt tension it caused the shaft and impeller to be cocked in the pump housing and not allowing the pump to pull water. If you were to try light tension on the belt ( enough that it doesn’t squeal) this might help get you pumping again. This is what I did on my boat and it has been cooling fine all summer, I will be rebuilding the pump over the winter. Best of luck! John
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Old school goin back to school!
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KENO
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Posted: August-13-2022 at 11:07am |
Just take off the inlet hose and look in the cooler, no need to remove it. If the strainer is doing it's job, there should be no junk in the cooler And you can check that the clamps are tight on the cooler inlet and outlet hoses.
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Skifunseeker01
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Posted: August-13-2022 at 12:57pm |
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That's exactly what is happening. Still not sucking but after a minute of running the backside of the pump is hot. I'll back it off but I saw a Sherwood RWP on EBay for $240 while on Nautique parts a rebuild kit was $320 and YOU had to do the repair.
I thought it must be the heat exchanger because I checked the rest of the water hose from the exchanger back to the intake in the hull and that was clear and replaced a portion of hose that was a little old. I'll back off the tension and see if that does it. Time to get a new RWP I guess. |
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KENO
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Posted: August-13-2022 at 5:13pm |
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Running a perfectly good pump for a minute with no water flow through it will make the housing hot, so I wouldn't be too quick to jump on the pump bearings as the problem.
Do it enough and that new impeller isn't new or good anymore
You did something to it that turned a pump that worked, into one that doesn't work What did the impeller you took out look like?
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Skifunseeker01
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Posted: August-14-2022 at 7:50am |
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The impeller looked okay- some minor wear but no pieces missing. The replacement is turning because the back of the RWP is getting hot. There isn't any water dripping from the pump or supply lines and I can't find any loose connections.
The only thing I haven't removed is the heat exchanger- so there must be an obstruction in that because the rest of the line is okay. Water should pass through it easily- so that is my project today. Any advice on what it should look like or how the water should flow through it. I did take the intake hose from the strainer off and looked and poked my finger in there- it felt like a screen was in there but nothing else. It is plastic- I was surprised- maybe the heat did some damage to it.
The pump does have a slight squeal when it starts up. The boat has 900 hrs on it- almost all skiing. Maybe the RWP bearings are worn, and it isn't sitting properly causing the heat. I have owned this boat for 15 years and it has been the most reliable piece of kit I own. I just can't figure this one out but certainly appreciate all the suggestions. |
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KENO
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Posted: August-14-2022 at 9:07am |
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I'd hook a length of 1 inch ID hose directly to the pump suction and let it suck from the bucket and see what happens.
Fill the hose with water as much as you can to make sure the pump is primed That would rule out any issues on the suction side of the pump or maybe show that you have an issue on the suction side. The transmission oil cooler has a plate with a bunch of small 1/4 inch or so holes when you look in the inlet or the outlet. It's all metal/ Water goes through those holes(tubes) and the transmission fluid is in the shell side flowing around the tubes If you take the outlet off of the cooler you can pour water in the inlet and it'll come right back out the outlet into the bilge No need to remove it from the engine or unhook the transmission fluid hoses. Shine a flashlight in one end and you'll see light at the other end. If your strainer stopped weeds etc, there's not much chance the cooler is your problem.
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Skifunseeker01
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Posted: August-15-2022 at 10:02am |
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Yesterday I pulled the pump off again. It is definitely the bearing on the flywheel pump. I'd like to thank everyone for the great advice and observations- I learned more about the cooling system in the last four days that in the previous 15 years. This is such a great place for SN owners!
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KENO
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Posted: August-16-2022 at 7:55am |
I guess you must mean the raw water pump
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Skifunseeker01 wrote: