Removing impeller housing and solving overheating

I have a 1985 OMC (GM I believe) 4cyl 3.0l engine with an OMC stringer outdrive. The model number on the outdrive is 983486 and the sn is 1401147.

This is kind of a two part question. First, I am trying to install a water pump kit in the outdrive upper gearbox. I have replaced the impeller before and it was cake, this time I am trying to remove the impeller housing and it won't budge. I have looked at many diagrams and pictures trying to figure out if it is attached by anything else other than the 4 bolts that hold the whole pump together and I can't seem to find anything. Is there anything else that holds the impeller housing in that I am missing, and if so, how would I remove it? My other thought is that it could have possibly corroded or rusted in there and is just stuck, any recommendations on how to remove it if that is the case?

Second, the reason I am replacing the impeller, housing, etc. is because at plain the boat is overheating but at idle it is not. The exhaust manifold and gooseneck are either new or very clean, and I have blown air and water through all of the hoses so I do not believe they are clogged, but I am going to try again. After doing some research and talking to a mechanic, I have come to the conclusion that exhaust might be leaking into the water pump or the pump might not have enough pressure because of a leak. If that is the case, what seals would need to be changed. This thread also basically explains the exact same problem I am having, but with a different engine.
http://forums.iboats.com/showthread.php?t=420685&highlight=omc+impeller+housing

Thanks for your help, it is greatly appreciated because I am going a little crazy.

Re: Removing impeller housing and solving overheating

anyone?

Re: Removing impeller housing and solving overheating

are you replacing the housing as well? Tap it lightly with a ball peen if you can. Use 2 screw drivers and try to pry it out. Chances are if it is metal it is corroded together. If I am not mistaken you can purchase a housing with the impeller in a kit?
Get a tub of water and place it under the outdrive, be sure the intake holes are covered with water and run the engine look to see how much water is being pushed out of the exhaust.
Have you considered a thermostat or a weak water pump. ( not the sea water pump). Pull the thermo and heat the water in a cup to 160 and see if it opens quickly.
Let me know the results.

Re: Removing impeller housing and solving overheating

Ok, getting the housing out was horrible... I don't think it had every been replaced in 24 years. I got it out by taking big lag bolts and created threads in the bolt holes. With that I got enough leverage and ended up dropping out the entire bearing housing and everything down with the impeller housing still stuck tightly in there. After a lot of liquid wrench and setting the bearing housing edges on a vice and tapping the impeller housing out from the back, it finally came out.

I also finally figured out the overheating problem. The thermostat was new and the engine water pump was replaced last year. Anyway, the o-ring around the impeller housing wasn't seated correctly and the housing had a small chip in it so exhaust was either getting sucked back into the impeller, or it simply couldnt build up enough pressure to push water through the engine. I replaced everything to do with the impeller and resealed everything I could find with some gasket goo stuff. It runs great now and I am really excited. Thanks for the help!

- Jacob