Overheating problems

[rlrobian]

I overheated my engine and I am trying to correct all that I messed up. The boat is a 1988 Century Fury with a Mercruiser 120 and a MR outdrive. The impeller is toast (may have been the original cause). The guide tube from the impeller housing to the water line melted. The housing for the impeller looks good, but will be replaced with a new impeller kit. I found (dug out) remnants of the exhaust water shutters in the cavity in front of the prop.

I am trying to get to the remains of the water shutter in the exhaust down pipe. I have removed the four hose clamps and freed the rubber tube. However I cannot figure out how to removed the tube from the two cast iron portions of the exhaust. It would look like I have to remove the exhaust elbow. There appears to be enough room to allow the elbow to pivot to the stern and pull from the rubber tube, thus allowing access to the lower tube and the remnants of the water shutters. I removed the two bolts holding the elbow to the water jacket but it will not come loose. I have whopped it with a 5 lb sludge and it will not move.

Questions: Am I going about this right ( I cannot find a write up in any of my manuals on how to remove the water shutter). I have read differing opinions of the risk/benefit of water shutters and I plan on replacing it.

Thanks for your help.
RL

 

[Condor1970]

My 1989 3.0L is the same. My muffs fell off when testing the engine, so I defintiely feel your pain. To get the lower exhaust off, and get to the shutter, I had to remove the exhaust elbow on top of the engine first. If you remove all the bolts, it may still be very stuck on there. That gasket will get very glued on over the years. After removing the bolts, I used a chisel on the side with a hammer, and gently tapped around the edges until it broke free. Keep in mind, you WILL NEED a new gasket for this, no matter what. So, order a couple of them, and keep one as a spare.

After removing the top elbow, use you chisel to scrape off all the gasket material from the elbow and the exhaust manifold. You need a very clean surface to install a new gasket that won't leak exhaust or water into your boat.

Also, if your guide tube was melted, I would not trust the pump housing at all. My pump housing was warped slightly from the heat, and I didn't even overheat my engine enough to harm the exhaust shutter like you did. Luckily, mine was still in good shape. Actually looked like new. I replaced it anyway, since I had it apart.

If I were you, spend the extra $40 and get a full pump kit with top and bottom housings, and replace the entire thing with new seals and gaskets everywhere.

 

[Fishermark]

I agree it sounds like the elbow is simply stuck. Instead of hitting it with a sledge hammer or using a chisel. I would recommended getting a 2X4 or something similar that you can use to leverage it off. It will be a good opportunity to see what condition the elbow and manifold are in anyway.

 

[Condor1970]

oops

 

[Condor1970]

I wouldn't use anything that puts a lot of leverage on that cast elbow. I know it is very strong, but you never know what could happen if you try to "pry" it off with a 2x4. Use the right tools for the right job. Please!!!

If you've ever watched mechanics remove exhaust manifolds on an engine, they will do the same as I described. If tapping it with a mallet won't break it free, then working around the edges with a chisel that cuts into the side of the gasket is usually best. Here is a simple description with pics to show that mechanics readily use a chisel to break free stuck gaskets and clean the gasket surfaces on the engine block of old residue to prep for new gaskets.

When using a chisel to do this, DO NOT pry with the chisel to try and pop the elbow off. Just tap it straight into the side of the gasket to wedge it between the elbow and the manifold, then jiggle it loose and move it to another spot, and tap it in it again, working around the edges, until the whole thing comes loose.

http://www.wikihow.com/Replace-an-Ex...anifold-Gasket

You can also spray around the edges of the gasket with some WD-40 to penetrate and soften the gasket material, as it is not a metal crush gasket.

 

[rlrobian]

Condor1970, thanks. While driving to work I started thinking about using a chisel. I seem to recall doing something like that years ago to get a stuck thermostat cover off. I will try it this weekend, and let you know.
Thanks
RL

 

[rlrobian]

A couple of good whacks on a chisel and it popped right off. The rubber bellows came off. NO WATER SHUTTER. Removed the next piece of iron piping and the rubber bellows below that. (Space is getting real limited about now.) Found what was left of the shutter. Just the center cross bar in place and in good shape. Used an inspection camera, from HF, and was able to check the rest of the exhaust plumbing to the gimbal housing. I could find no shutter pieces. Removal of the cross bar (with the rubber off looked to be in good condition) was not going to be a very simple task with the amount of space I have to work in. Final decision, leave it in place, go without the shutter and put her back together. I will verify that none of the shutter is in the outdrive. Put a new pump kit in and test. Thanks for your help.
RL