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Raw water pump works in driveway...not in lake???

Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Boat Maintenance
Forum Discription: Discuss maintenance of your Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=51641
Printed Date: January-15-2025 at 10:00am


Topic: Raw water pump works in driveway...not in lake???
Posted By: jackkloepfer
Subject: Raw water pump works in driveway...not in lake???
Date Posted: June-25-2024 at 3:57pm
Hello, all.  Running a GT-40 in a '96 super sport.  In my driveway...detatced water filter...clamped a hose to the water intake...placed other end of said hose into a bucket on the ground next to my boat + trailer.

all good.  Sucked up about 10 gallons of water...temp stayed at 120, and I felt the impeller housing to ensure it was cool-to-the-touch.


Then took her to the ramp.  Launched.  reversed back about 40 yard.  Temp started to climb past 120...130...140....oh S****!!!

felt the impeller housing...super hot.


Any idea why I'd be able to pull water just fine from a bucket...but not from the lake?


Replies:
Posted By: Wilhelm Hertzog
Date Posted: June-25-2024 at 4:43pm
Clogged thru-hull intake grate and/or strainer?

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1982 Ski Nautique PCM351W RR II Velvet Drive 10-17-003 1:1 II PerfectPass Stargazer
Do not go gentle into that good night. Rage, rage against the dying of the light.

Posted By: RealDeez
Date Posted: June-25-2024 at 6:21pm
By intake, do you mean the intake side of the RWP, or some other location?  You may have bypassed some potential leak locations.


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Lake James, IN
93 Sport Nautique

Posted By: LooseScrew22
Date Posted: June-25-2024 at 8:35pm
My '95 SN (not a GT40) came with a hose adapter inline after the strainer, but i added a ball valve so i can control the water from flowing out the intake. I leave the valve open on starting then shut it off most of the way when running.  My temp stays at 160 degrees. I expect your intake is blocked somewhere or your impeller crapped out

Posted By: Jonny Quest
Date Posted: June-25-2024 at 11:24pm
Sounds like you fried your impeller.   Time for a new one.  If the impeller housing is hot…impeller is toast. 

Your raw water hose should have a bit of a “downhill“ run to The impeller.  That helps maintain prime so that the impeller has water to maintain a suction seal.  Almost like a P trap in a sink drain.  

JQ


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Current
2003 Ski Nautique 206 Limited

Previous
2001 Ski Nautique Open Bow
1994 Ski Nautique Open Bow

Aqua skiing, ergo sum

Posted By: MrMcD
Date Posted: June-26-2024 at 2:38am
Maybe when you re installed the filter after your bucket test the hose did not seal completely.  If the hose allows air to be sucked in the pump will never suck water.   

JQ is correct, after running your pump dry and getting it hot the odds are very good the impeller fell apart.   If it did, you will need to search all the coolant lines till you find all the missing parts of the old impeller.  If parts of the old impeller are in your system you will have cooling issues till you dig them out.

Almost all of us have done this or been there when a friend did it.  I doubt any of us did it twice though.

I was 25 when I bought my first Nautique, a 1978 purchased in 1982, at that age I flat out loved the sound of the engine firing up with the straight pipes and no mufflers.  Fired it up several times just to hear it before taking it to the water the first time to find out I had wiped out my impeller.  Lesson learned.

Read up on adding a TimmyT to your boat cooling system, it is much easier than a bucket for driveway tests.


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