PDA

View Full Version : Odd Cooling Problem...Low flow?? ***!!


learjet2230
05-21-2012, 07:42 PM
So after about 3 months downtime doing a "mini-resto" (http://mastercraft.com/teamtalk/showthread.php?t=46123) I got the fever as I watched my neighbor idle out in his Malibu and said thats it I'm gettin this damn thing in the water. I went out did everything I needed to get this thing water ready, including put in a new impeller. I did the ol' 5 gallon bucket trick and leak checked everything, multiple times!!! I also noticed how my hose was having a hard time keeping up with the demand of the boat at idle. So I had to essentially fill the bucket to the top...start boat and then shut off maybe a minute or so later and repeat. So I know this thing was suckin!!! Hook hose back up, drop boat, do a few test runs, do some carb tuning. And during all this I notice the risers are hotter than Hades.....with the boat at idle. I always remember being able to lean on these and touch them (with boat runnin, if off they heat soak and get real hot). So I bring the RPM's up a bit and they begin to cool down...not a lot, but to where you can keep your hands on them for a min or two. Let the boat idle again....and they get smokin hot again. Looking at the temp gauge...all is normal....160 Tstat....temp ranges from 140-160 depending on throttle etc. Next thing I did was pull the pipe plugs out of the risers...and...NO WATER!! Started boat and after about 5 seconds...a spray of water...not a rolling stream that I seem to remember when I put the manifolds and risers on about 4 yrs ago. After some head scratchin, we decide to take the boat out for a family jaunt. We get about 30 min from the house and the bearings in the raw water pump decide to let loose...i mean grinding, screeching, and smoking. I thought I was on fire. Pop the hatch...make an assessment and start dumpin water on the bearing area of the RWP. Now I'm think what the hell does this have to do with a low flow problem? We idled back peridically dumping water on the bearing...but it never got hot again. So we monitored it every minute or two after being under power and it was fine. Again boat never overheated. Boat is currently on trailer torn down. Here is a list of things I have checked. I have a feeling this is two problems not related...parts on oreder...thoughts??

Tstat opens at 160 in pan of water (im replacing it anyway)
Raw Water Pump is removed..bearings are shot (I think its original...new pump ordered)
Circ pump is 4 years old, its off, no anomolies..looks good
Block is clear...reverse flushed it...few small chunks, nothing abnormal

So the RWP is shot...bearings just said im done...no biggie, but why am I losing water flow. Again I have an idea but I want to hear thoughts and opinions first as not to sway your thinking.
Cheers

mikeg205
05-21-2012, 07:55 PM
Getting air int he system somehow...something got old rusted and is preventing suction?

Nvrgvup
05-21-2012, 09:00 PM
Like said it may be an air leak. Maybe the pump bearing is leaking air in. Darn vacuum leaks are tough to find. Check all hoses everywhere, clamps, strainer in the hull and the screen in the trans cooler. Clean and replace anything suspicions. All the hoses on mine were wire wound. At a minimum the hoses under vacuum and tight bends have to be wire wound so they don't collapse.

Maybe try connecting a garden hose on the outlet of RWP to the engine and see if you have good flow into the manifolds and out the rear with the engine off. If you can get enough flow out of your garden hose you could run it like this w/o the RWP to try to eliminate some things. Just watch your temps.

If you have a 351 make sure to put the RWP in the correct orientation. Spoken from experience, easy to get the top and bottom swapped.

mikeg205
05-21-2012, 09:27 PM
Is there any preventative maintenance that can be done to avoid catastrophic failure like that?

learjet2230
05-21-2012, 09:44 PM
Like said it may be an air leak. Maybe the pump bearing is leaking air in.

Isnt the seal on the pressure side of the pump? If it were an air leak it would have to be between intake to RWP...agree?

learjet2230
05-21-2012, 09:47 PM
Is there any preventative maintenance that can be done to avoid catastrophic failure like that?

Got me...i figured it was either a bushing or sealed bearing....

Nvrgvup
05-21-2012, 09:57 PM
On the RWP? Tough to tell. You now have me thinking about my bearing. I like to have good hoses with these really nice german hose clamps I found. Check the screens and filters regularly. I commonly find some form of seaweed in the trans cooler screen.

On the older Sherwood RWP's like on my 351W there is a brass plate between the two halves of the housing that periodically needs replaced if it is grooved. Behind that brass plate debris and scale can accumulate around the shaft bearing.

Watch for drips, noises, and I like to give things the shake, wiggle, spin and feel test.

During layup it is also a good idea if possible to loosen the tension on the drive belts. However I have to leave myself a note on this so I remember in the spring to tension them up.

Nvrgvup
05-21-2012, 10:10 PM
I see your point. I don't know how the bearing would leak.

Sherwood has a great tech guide for the pump here:

http://www.sherwoodpumps.com/FileAttachments/Marine-Distribution/en-us//Literature/MPG_3047_09959_TECH.pdf

Worthing skier
05-22-2012, 09:16 AM
Hi there


Have you had a close look at the raw water main shaft to flange fitment.
This should be an interference fit .
I have seen this spin before hence the raw water pump will not be turning at engine speed .
This can be caused by poor alignment of the raw water pump and also premature failure of the bearings .
If this is the case you can get your local machine shop to re bush the front crank flange and press in the shaft .

good luck

Kevin

EricB
05-22-2012, 02:28 PM
The RWP can draw air vs. water. This can contribute to your flow problem. Since your RWP has now gone south, install the new one and re-test. I do not think you need to go much further than your old failed RWP. The reason is that is what happened to mine too.

TRBenj
05-22-2012, 02:44 PM
Agree that the RWP could very well have been the culprit. Pulling air past the seal will cause the engine to overheat- though more commonly at speed than at idle. Do double check all of the hose connections between the pick up and the RWP though. Make sure the clamps are TIGHT.

learjet2230
05-22-2012, 07:22 PM
Yep...I think she was sucking air somewhere....now after thinking this through, I never checked the hose clamp at the cooler after hooking it back up. Im pretty sure I secured it but I cant be 110% sure I cranked on the clamp. So...I have a brand new RWP coming along with a thermostat and all new gaskets for the Circ pump, etc. Supposed to be here tomorrow. I'd rather it happen this past weekend than on Mem day weekend. keep ya posted.......cheers

learjet2230
05-23-2012, 08:36 PM
Well...new RWP and bracket, new Circ pump gaskets, new Tstat and gaskets. Checked and tightened all hose gaskets. Had great flow....and...the new Thermostat wouldn't open. Boat got up to 190 at idle and sat there and the thermostat housing was stone cold!! I was like...you gotta be freakin kidding me! I put the old one back in and she wont go over 150 at idle. If I shut the boat off and let it heat soak gauge shows 160ish and housing gets warm, so I know the old one is opening. Risers are warm at idle and seem to be ok. I may change the riser gaskets just to be on the safe side. I will be calling SkiDim first thing in the AM and raising the issue.

Table Rocker
05-24-2012, 12:01 AM
Well...new RWP and bracket, new Circ pump gaskets, new Tstat and gaskets. Checked and tightened all hose gaskets. Had great flow....and...the new Thermostat wouldn't open. Boat got up to 190 at idle and sat there and the thermostat housing was stone cold!! I was like...you gotta be freakin kidding me! I put the old one back in and she wont go over 150 at idle. If I shut the boat off and let it heat soak gauge shows 160ish and housing gets warm, so I know the old one is opening. Risers are warm at idle and seem to be ok. I may change the riser gaskets just to be on the safe side. I will be calling SkiDim first thing in the AM and raising the issue.You can test the new thermostat in a pan of water on the kitchen stove and see what it is doing.