Mercury 500 water pump replacement questions the

[Kanook]

I just picked up an old ‘65 Fiberform with a Merc 500 thunderbolt. I’m going through the lower end replacing the water pump and have some questions. My stock pump and the replacement pump both have a raised tube for the outlet water to the engine and both are internally tapered and also have a groove missing from the side. (See pictures) Are there any seals that help seal the pump to the copper pipe or is it just designed to pressure fit? And what’s the purpose of the slit up the side? There was nothing in that upper section when I pulled the original off but I’m also discovering that a previous owner half assed a lot on this motor. And second part. On the impeller side of the same passage my original had a long rubber insert and a small plastic piece that sealed against the main pump gasket. The new pump has these same pieces and I’m wondering if these were installed correctly and if that’s how I put the new one together? Thanks in advance for any info.

 

[Kanook]

Here are the pieces I was referring to.

 

[merc850]

The long piece goes into the outlet - taper facing up, the round piece looks like the slinger which goes on the driveshaft after the pump is assembled. Push it down until it's just above the pump housing but not touching. You'll also need the long plastic piece that guides the water line into the pump Nr.35 in diagram. Use some grease on the WT seal to make the water tube slide in easier.

 

[Kanook]

Thanks. These older pumps don’t seem to use that plastic riser like the diagram you posted shows. That’s why I was a little concerned on how well the pump will seal to the copper pipe. And that small part is too small for the slinger and is hard plastic. I did get the larger rubber slinger in the kit though.

 

[Kanook]

So I’m getting this figured out slowly. The parts diagram makes it look like both the rubber sleeve and the plastic washer may go on the inside of the pump and that’s how it was when I dismantled the pump. However the online service manual shows that the plastic washer and rubber sleeve go on the outside and inside the small riser built into the top of the pump. Makes more sense and probably explains why I wasn’t pumping sufficient water.

 

[merc850]

Yeah I posted the wrong LU image, the plastic piece does go below the WT seal.

 

[Dionw]

So I’m getting this figured out slowly. The parts diagram makes it look like both the rubber sleeve and the plastic washer may go on the inside of the pump and that’s how it was when I dismantled the pump. However the online service manual shows that the plastic washer and rubber sleeve go on the outside and inside the small riser built into the top of the pump. Makes more sense and probably explains why I wasn’t pumping sufficient water. View attachment 271388

Hi mate, just wondering, where did you find the online manual? I have a thunder bolt 500 50hp and can't find one for parts