2004 22V MP 5.7 Engine. Weird cooling issues...

[doubelsnaggle]

Engine overheats every time we launch. Let the engine cool off, then start it and the temp will come down and steady to 175 for the day.

Replaced bad impeller.
Replaced thermostat.
Flushed out the inline coolers.
Flushed out the pump.

Still overheats after launch.

The little pump that sticks off the front of the engine (the one with four little bolts on a plate and a rubber impeller under that plate) is the raw water pump, correct?

Please, any comments or help is greatly appreciated.

[doubelsnaggle]

Yes, it was. But I flushed it all out Im fairly sure. The output side of that pump is a cooler and it would have blocked most of the pieces, I flushed all the hoses backwards.

[chpthril]

So it only overheats on the initial launch? What temp does it get up to before you deem its running hot and shut it down to cool? Runs fine the rest of the day? What temp thermostat did you put in? 175* seems a tad high for an open cooling 5.7L. Im thinking its a problem with the raw water pump sucking air and not priming. Thats my gut right now.

[doubelsnaggle]

That was another persons feeling as well.

We shut it off at 220. Engine is too hot to touch. Risers are too hot to touch and faint smoke from cooking off exterior oils.

Yes, unless you let the boat sit for a couple hours then it may do it again, maybe not. I put in the stock thermostat, whatever that is.

I guess next test would be to launch and pull the output hose of the pump and see if it primes itself or not.

What is there between the raw water strainer and the pump? Vdrive and? Is there a screen inside the vdrive?

[chpthril]

Water flow will come in the pickup, go through the V-drive, which is just an open cavity on the Walter IIRC, then on to the transmission cooler before entering the raw water pump. The trans cooler can trap lake debris, but this would result in an overheating problem either any time the engine was running or when at higher RPMs do to decreased flow.

[Ruger761]

When you first back the boat in (before it gets hot) and start it, pull one of the winter plugs out on the side of the block see if your getting any water into the block is the easiest way to check. If your not priming up, you might have toasted another impeller running dry. Also if you twisted the impeller the wrong direction installing it, it will rip the fins off as soon as you start the engine.

Some route from the v-drive to the raw water then to the transcooler before intering the engine circ pump. If you shreaded the impeller you need to pull the exit hose off and follow it all the way to the engine making sure you got all the rubber out.

[Ruger761]

If he had shredded the impeller again it wouldn't cool the engine on the restart. I seem to remember some say that an impeller can distort the shape of the raw water pump housing and it is best to replace the entire housing.

Woops I missed reading that one. TeamAllen is right on the money and it can destort the housing.

[bryancm]

Might be totally obvious, but the belt is plenty tight right? You can see the impeller pulley turning? I just ask because I've seen a situation where the belt was just not tight enough to get that thing spinning at first start.

[doubelsnaggle]

I just pulled the new impeller I put in to check it. Here are the pics. Found one more piece of the old impeller. But its not enough to block anything.

The old impeller shredded, because it was really old.

Belt is perfect.

This blue impeller is one of the more expensive ones that allows 15 minutes of run dry. So its not easily destroyed.

Im going to try back flush through the vdrive.

How does this pump prime itself? Does it dry prime every time you start the engine?

photo 1.jpgphoto 2.jpgphoto 3.jpgphoto 4.jpgphoto 5.jpgphoto.jpg

[Ruger761]

The pump is designed to dry prime. It will typically hold water in the housing and intake hoses though after you dewinterize, especially with a v-drive. Did it have any water in it when you pulled it apart and pulled the hoses off?

[boatwakes]

Is the o-ring installed? I don't see it in the pics. It goes in the groove around the housing.

[doubelsnaggle]

Yep oring was installed.

No, no water spilled out. Not even when I pull the hoses off the pump. Is there a check valve somewhere? I do seem to remember that a lot of water drains out the strainer when the boat is on the trailer.

[Ruger761]

No there shouldnt be any check valve. You should have had some water in the hoses maybe not 100% full but at least say 50% full depending on how they lay with the hull and engine.

What color impeller did you have before blue or black and did you ever have any issue before? If the hoses are clear with no left over rubber in the, Im starting to wonder if the improved blue material isnt working well in your pump housing.

[doubelsnaggle]

There was a black one before. Im going to install the spare black one I have and see if there is a difference.

[Ruger761]

Im wondering if the blue compound isnt creating a good enough seal under the inital start up, cooler condition, then after it finally gets hot enough it softens some and finally creates a good enough seal to prime the pump up. We have issues with different oring compounds on our tools depending on what the inital temperature is. I bet the black one will solve your issues.