Merc 500 Water Pump Base REALLY STUCK

[cmayhle]

I have recently been working to rebuild my circa 1976 Merc 500, 50 (Serial 4418971) water pump. When I took it apart, as expected the impeller was old and thrashed. I should say that I have owned this motor for about 12 years, and I run it every year but only for about 2 hours a year, so it has had very little use from me. I didn't really see bad things happening to the pump base, but since I had purchased an entire pump rebuild kit and have seen others here suggest to do the whole thing at this age and interval, I decided to replace everything. Well, the pump base is absolutely fused into the seating port. I started with using every normal pry technique (Per the service manual and posts here suggestions) but couldn't budge the base. Over time, I have used increasing amounts of force and persuasion, and now the pump base is mostly broken away, but still absolutely fused into it's seating (See attached photo). I have been careful with the drive shaft, it still freely rotates, and although one of the oil seals has been broken out of the base and removed, you can see the other oil seal still in the pump base. It also is not jammed, in fact it will move and partially rotate in the base, so I know for sure the problem is in the actual perimeter/O-ring seating of the pump base. I have drained and opened the lower unit of gear case oil, and have applied heat to the surrounding casting via a paint heat-gun to warm everything up short of any open flame. Still will not break loose. I don't know what else to try to get the remnants of this base out of there! Any suggestions will be greatly appreciated!

 

[carholme]

Re: Merc 500 Water Pump Base REALLY STUCK

Did you remove the Flushing screw, the larger one located aft of the Vent screw?

Gerry

 

[cmayhle]

Re: Merc 500 Water Pump Base REALLY STUCK

I have gleaned from the service manual and parts diagrams that some of these motors were equipped with flush plugs and some were not. It appears this one is not, as there are certainly no other screws or mechanical penetrations into the gear case casting on either side.

 

[DSMBoater]

Re: Merc 500 Water Pump Base REALLY STUCK

i have a merc 650 that did the same thing. I basically had to use a small hammer and chisel and very carefully chisel away all the plastic to get it out. Took about an hour but I didn't see any other way to do it. Mabe put some lube around the base and let it sit, to loosen it up if at all possible.

 

[cmayhle]

Re: Merc 500 Water Pump Base REALLY STUCK

Thanks for that DSMBoater, that is about where I am at with this.

Does anyone suppose if I took this to an outboard service shop they would have some kind of special puller to deal with this kind of issue, or would they basically just have to dig it out piece-by-piece also?

As far as some kind of substance around the perimeter to try to soften up the bond, what would be the best choice for this situation?

Thanks!

 

[cmayhle]

Re: Merc 500 Water Pump Base REALLY STUCK

Just an update on my water pump base removal, in case any of this information may be useful to someone else that finds this thread.

You can surmise from the photo what it took to finally get the base out of it's seat. It had to be carfully carved out with wood chisels for the most part. The largest intact piece with the seating ring finally popped out. I had used some PB Penetrating Catalyst over several days, and with the help of a narrow and stout parting tool I was able to break it loose.

If I had it to do over (And I hope I never do) I would use the Penetrating Catalyst sooner in the process. I really think it helped to finally soften up the fused base-to-casting connection and allowed the tool (Biting into the plastic at several places) to finally break it loose. I really think this water pump base had never been removed from the gear housing casting since it was installed in 1976.

Thanks again to those offering assistance and ideas.