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

[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.

[doubelsnaggle]

I notice that my pump is loosely mounted. I mean not loose. But I can twist it a little bit.

[boatwakes]

Let us know after you try the spare because: the crank mounted johnson pump is also used by volvo penta marine as well as their belt driven unit. However, Volvo issued a TSB regarding impellers because the drive for both pumps was the same but the internal pump housing longitudinal dimensions on the crank pump were slightly greater than the belt driven pump. Therefore when people would buy the impeller and not know about the difference, the crank pumps would all have the same issues you're having at start up. The impeller must seal with the faceplate in order to create suction and pressure and the slight difference in impeller length will cause the same problem. From your pictures the impeller looks slightly recessed in the housing. What model number is that impeller?

[doubelsnaggle]

This is the blue one that I installed.

http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

I did notice that there is a difference in the depth of the impeller front and back. If that makes sense. But it doesnt say which is which on the actual impeller. I assume there is a right and wrong way to put it in. Im going to compare it to the black one and get back to you all.

[Rafterman]

I am having the exact same problem - overheat, let it sit, fire up again and temp is maintained at 175. When I replaced my impeller this season it was only misshapen, it had not come apart.

[Rafterman]

Also, I am using the stock recommended impeller (black).

[doubelsnaggle]

Yours overheats right at launch?

[Rafterman]

After I was under power for about 10 min (happened today). All of a sudden temp just shot up. I immediately shut the engine down. About 15 min later I started up and temp went right back up. Another 15 min I decided to start it for short term to start heading for shore and temp began rapidly falling then settled at 175. It took me about 20 min to get to shore and I did not get above 175.

[doubelsnaggle]

In comparing my two impellers. The blue one has a large indent in the middle around the core that the black one does not. The black one is an actual Johnson impeller. Plus the teeth are much bigger on the spline inside the johnson impeller. Im thinking there are some wacky impellers out there. I wanna bet that when I put the black johnson in the pump, it will be fine.

[Rafterman]

Please let me know how it works. I have seen this same issue in other threads but no definitive answers. This thread is the first I have seen that there may be slight variances in impellers claiming to be the correct part #. I am going to double check mine and make sure it is a Johnson and not a no-name brand.

[doubelsnaggle]

I may be able to test the theory out tomorrow. Depending on the wind.

[boatwakes]

707.jpg One of these gauges will help too. Again, it doesn't matter which way you put the impeller into the pump, it will work the same. The shorter impeller will not make an immediate seal with the wear plate and cause the overheat from lack of water flow.