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Old     (billcallen)      Join Date: Jun 2011       06-21-2011, 10:42 PM Reply   
I know i'm about the millionth person with an overheating issue, but i couldn't find any with a problem at idle. I got the boat out a couple days ago from storage and decided to try summerizing it myself. Got all the plugs in and ended up with one small hose clamp leftover (which i believe is for the heater so i am not to worried about it) Fired it up got no water and overheated. Got into the impeller housing saw the impeller was bad put in a new one, and fired it up with a hose jammed in to the intake on the other side of the vdrive and it ran fine. Headed to the lake today got in no problem ran for maybe 10 minutes got to where i wanted to start wakeboarding and overheated, let sit to cool down started again and it started to cool down got up to speed again and seemed fine. Started wakeboarding no problems until at idle it would overheat then we would start trolling and it would cool down get up to speed for wakeboard and would run great at 160. Stop again idle for a couple minutes and it would heat back up a couple of times it ran fine at idle but the majority of the time it overheated any suggestions? Thanks
Old     (moto817)      Join Date: Jan 2011       06-22-2011, 1:54 AM Reply   
Did you clean the rubber impeller parts out of the downstream equipment on your cooling system ?. At higher RPMs there could be enough pressure to get cooling water by the obstructions. What motor, Is this a closed cooled or freshwater cooled motor ?
Old     (billcallen)      Join Date: Jun 2011       06-22-2011, 4:25 AM Reply   
Hey i haven't really looked for things downstream yet i thought all parts of the impeller were accounted for but i guess that is my logical first step. The motor is a Merc 5.7 black scorpion, it is freshwater cooled. Also while out i had a little bit of squeaking from the belt intermittently at idle, i guessed it was just the old belts get some water on them and they squeak but could this have anything to do with it? Did i tension the belt wrong when i put it back on?
Old     (kdr)      Join Date: Feb 2003       06-22-2011, 5:02 AM Reply   
I'd look at the impeller again. When I had one go on me, I only noticed it at idle. When the boat was moving, enough water was being forced into the cooling system to make the temp go down. As soon as I would slow down, the temp would shoot up.
Old     (sidekicknicholas)      Join Date: Mar 2007       06-22-2011, 5:39 AM Reply   
When the boat was moving, enough water was being forced into the cooling system to make the temp go down. As soon as I would slow down, the temp would shoot up.
+1.... check it again
Old     (05sante)      Join Date: Jun 2011       06-22-2011, 5:40 AM Reply   
Sounds like you have a vacuum leak somewhere. At idle there isn't enough vacuum to pull enough water through but as engine speed increases the vacuum builds and it starts circulating enough water to cool it back down.

Check all your hose clamps, water strainer gasket, etc. The fact that you have a leftover clamp should be the red flag.
Old     (sidekicknicholas)      Join Date: Mar 2007       06-22-2011, 5:51 AM Reply   
What kind of boat is it?
Sounds like you have a vacuum leak somewhere
Our older Nautique had a fresh water filter on it (worthless) and it had a tiny tiny crack that caused a vacuum leak.... we just ended up removing the stupid little thing
Old     (humboldt9)      Join Date: Jun 2004       06-22-2011, 10:09 AM Reply   
+1 for checking for downstream for debris. I'd also check to make sure you have the impeller going in the correct direction as well.
Old     (ottog1979)      Join Date: Apr 2007       06-22-2011, 10:29 AM Reply   
+2 for downstream debris. I had the same problem 18 months ago on my Sanger with 350 Mag engine. At idle, it got hot. But at speed it seemed to be fine. The impeller had lost a few blades. They headed down-stream and were jammed up on the filter on top of the tranny. Just follow the hose from your water pump and you'll find it.
Old     (chexi)      Join Date: Jul 2009       06-22-2011, 10:31 AM Reply   
So that we are all clear on terminology, isn't "fresh water cooling" a closed loop system and "raw water cooling" an open loop system? It's easy to call a raw water system "fresh water", because you use a raw water system in fresh (as opposed to salt) water. So which does the OP have, a fresh water or raw water setup?
Old     (chexi)      Join Date: Jul 2009       06-22-2011, 10:32 AM Reply   
I meant, easy to mistakenly call...
Old     (billcallen)      Join Date: Jun 2011       06-22-2011, 12:40 PM Reply   
Will probably go ahead and take the impeller off again today and take another look at it. The boat is a 05 Calabria Pro-V. Where is the water strainer, is that the filter in line right after the V-drive before the impeller? Made sure to bend the new impeller when i put it in so the blades were going the same direction as the old one threw some grease on as a i put it in for good measure. I'll definitely check the fliter on top of the tranny good place to start i guess. Scott you are correct it is a Raw water cooling system my mistake. Thanks for the responses i'll see what i can find this afternoon
Old     (chexi)      Join Date: Jul 2009       06-22-2011, 1:37 PM Reply   
You should have a water strainer somewhere between the impeller pump and the thru-hull intake. At lof of vaccuum leaks are due to the strainer bowl not being on tight or the flat gasket being missing. People often lose this gasket when putting it back together in the summerizing process.
Old    alanp            06-22-2011, 1:56 PM Reply   
im having the same damn problem. ive done everything checked for vacuum leaks, removed every hose to check from blockage and check the impeller a million times and verified it was on correctly with the dealer. yesterday i dropped it off at the mechanic's. im over it.
Old     (billcallen)      Join Date: Jun 2011       06-22-2011, 11:47 PM Reply   
So we pulled the impeller out again today looked fine still looking new had some of the grease still on that we started with, pulled the line from the impeller to whatever the first hose clamp is (i'm assuming trans cooler) found a few piece of old impeller stuck to the screen, got them all pulled and put everything back together. Went to fire it up from the hose stuck into the line between the water strainer and the impeller, and had an initial suck of water then nothing waited 30 seconds or so and got nothing out of the exhaust and shut it down as it was starting to get hot. Pulled the line for the intake to the water pump and had steaming hot water there. Should i assume that the water pump is bad? Had it replaced about 2 years ago, but i pulled the thermostat off and did a boil test on it and it opened at 160* so i'm assuming it is fine. Any suggestions? thanks
Old     (chexi)      Join Date: Jul 2009       06-23-2011, 11:44 AM Reply   
I realize this is a stupid question, but are you absolutely certain the hose was on and not kinked somewhere? The scenario you describe sounds impossible if the hose was on and there was no blockage on the input side.
Old     (will5150)      Join Date: Oct 2002       06-23-2011, 12:08 PM Reply   
are you sure youhave the impeller housing oriented properly? Some of these can be mounted in two different orientations and it won't draw water- went through this on my Tige a few years ago. I reseated the impellar housing and it worked great.
Old     (billcallen)      Join Date: Jun 2011       06-23-2011, 12:41 PM Reply   
Hose was on stuck in to the intake hose for the impeller and had plenty of water flowing to impeller, my impeller housing can only go on one way as there is a bolt on the top that holds it to another bracket on the motor besides the two bolts that hold the impeller housing to the block, I will check again though just to make sure. have no idea as to the problem at this point
Old     (bftskir)      Join Date: Jan 2004       06-23-2011, 1:12 PM Reply   
you had mentioned a belt making is probably too loose, tighten the belt.
Old     (moto817)      Join Date: Jan 2011       06-23-2011, 1:16 PM Reply   
Just remembered we had this problem with my buddies nautique a few years back and the issue was that they gave us an impeller that was a slight bit shorter than the right one that we took out. Double check your impeller dimensions to be the same as the one you took out and that it is the correct replacement part. If it is not sealing on one side then it would be hard for the pump to pull suction until you hit higher rpms
Old     (chexi)      Join Date: Jul 2009       06-23-2011, 4:02 PM Reply   
I know that on older Nautiques there are 3 bolts, and they can go in upside down, and if they go in upside down, you get no water going to the engine.
Old     (billcallen)      Join Date: Jun 2011       06-23-2011, 4:22 PM Reply   
the imeller we took at was to warn for me to get any information out of it how do i know what impeller needs to fit in there? The impeller housing is a six bolt system for just to hold together, and 2 for going through and mounting to bracket. (and one more to hold to bracket on top of impeller housing) The one we put in seems fine enough very tight fit going in fins have a very good bend to them once inside the housing, i believe its the water pump will be taking that off next. Any other suggestions?
Old     (billcallen)      Join Date: Jun 2011       06-23-2011, 6:07 PM Reply   
Also new impeller was same length as old one if thats what you were meaning sorry i miss read that. We got the water pump out and all looked fine got some new gaskets put on. Waiting for tomorrow morning for a new thermostat kit to put that back together and try again. My next guess is to check the timing. I'm just still baffled on why i couldn't get any water coming out of the exhaust.
Old     (humboldt9)      Join Date: Jun 2004       06-23-2011, 8:40 PM Reply   
Keep us updated on this one. From what you're describing it doesn't sound like a thermostat issue. As mentioned above it sounds like a vacuum leak or some type of blockage. When you pulled the old impeller debris does it match what was missing from the impeller (like putting a puzzle back together)? Are you sure the serp belt has enough tension at idle, you mentioned you had some squeaking from the belt?
Old     (billcallen)      Join Date: Jun 2011       06-24-2011, 10:30 AM Reply   
So the debris that i got out of the screen from the old impeller was more than i had for the bad impeller and nothing was off of the new impeller, so i'm guessing the old owner toasted an impeller and didn't look for anything. This morning got the thermostat back on new gaskets and stat, also new gaskets for the water pump. Put all back together stuck hose in and turned water on, and tried to fire up boat. There was an initial suck of water down the line and then it seemed like it wasn't sucking any more. No water out the exhaust, made sure the belt was tight. Assuming i have a leak in my impeller somewhere saw in another forum that was some guys issue with his, so i guess i'm back to breaking the impeller pump again.
Old     (billcallen)      Join Date: Jun 2011       07-13-2011, 11:30 PM Reply   
Got some work in on the boat again today and thought i had it working just fine got it fired up no heating up but wasn't getting water out the exhaust reved up a little bit to about 1200RMPS got water out the exhaust boat heated and then cooled down to 160* exactly as it should have. Slowed the motor to 1000 RPMs everything still fine water out the back backed the water even down to 800 motor was still alright but gauge was starting to flirt with a higher temperature. Dropped the boat to idle at 600 RPMs and big suprise no water getting sucked in and overheated. I am just wondering if maybe i could just bump the idle up a little bit is that low by regular standards? Or is this just more signs that it points to an air leak? I have removed and checked and tightened all hoses between the water intake and the impeller haven't seen any leaks or water coming from the engine. Is there any good way to check for an air leak any other suggestions? I think the boat is headed to the dealership the next oppurtunity but i don't know what i'll be able to get it there.
Old     (bftskir)      Join Date: Jan 2004       07-14-2011, 7:30 PM Reply   
did you tighten the belt ?
600 rpms is about right for idle faster will cause you troubles.

kinda mysterious problem you got here
Old     (mikeski)      Join Date: Aug 2003       07-16-2011, 11:40 PM Reply   
like all the others have already told you, most likely it's the impeller, a leaky strainer or both. I still have the one from my 1995 on a shelf. I bypassed it one weekend after replacing the impeller 2 times. The cause was the strainer. Same issue, idle overheating.
Old     (bradb)      Join Date: Oct 2003       07-17-2011, 6:36 AM Reply   
I had a problem like this a few summers ago with my nautique. Turned out to be a blockage in the water jackets of the exhaust risers. At speed it would force enough water through, but at idle it couldn't. It was rusty bits that had flaked off the inside of the exhaust risers.
My mechanic told me to remove my exhaust hosing (hose & clamps off the end of the exhaust risers) and you will see an outer jacket where the water comes through. Talk a wire clothes hanger or something and push any debris back down into the exhaust riser. Then, flush the riser through the drain plug on the riser. Fill with water a few times (by starting the boat up) and drain the risers again.
Good luck tracking down your problem,


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