1971 7.5 Mercury Impeller Stuck

[111torrance111]

The water impeller seems welded to the shaft, is there any tips on how to remove without damaging anything else.<br /><br />Also when I look @ the drive shaft it doesn't look centered inside of the impeller housing, but the housing dosent look worn out. Is this normal?<br /><br />I'm a rookie to this site, but it seems like it offers great suppot.

 

[emckelvy]

Re: 1971 7.5 Mercury Impeller Stuck

You'll need to split the brass insert that the rubber of the impeller is bonded to. A very sharp, thin putty knife or thin-bladed screwdriver, sharpened to a chisel-point, should be able to split it. Then you'll be able to drive a tool between the insert and the driveshaft in order to loosen it enough to get it out.<br /><br />BTW the driveshaft is perfectly centered in the lower unit, it's the impeller cup that's offset. This offset is required in order for the impeller vanes to compress on one side and expand on the other, causing pumping action.<br /><br />Besides a new impeller, your impeller key is likely to be buggered-up by the above process, so you might as well pick up one of those, too. Plus an o-ring for the driveshaft where it enters the crankshaft. Check the stainless insert in the pump body, and the stainless pump plate, for wear and replace as necessary.<br /><br />Check the other portions of this site for good FAQ and info on replacing your pump and performing other types of maintenance.<br /><br />HTH and G'luck......ed

 

[111torrance111]

Re: 1971 7.5 Mercury Impeller Stuck

Thanks Ed Mc.<br /><br />I should be able to perform the above task, however I have one more question in regards to the drive-shaft. Shouln't the shaft simply pull out of the lower unit, I don't see any release bolt/screws holding it in?

 

[DHPMARINE]

Re: 1971 7.5 Mercury Impeller Stuck

You have to dissassemble the gearcase to remove the driveshaft.The pinion gear on the bottom of it is held on with a retaining screw and washer.<br /><br />DHP

 

[111torrance111]

Re: 1971 7.5 Mercury Impeller Stuck

Thanks for the information, hopefully when I get the impeller replaced I'll have a nice little engine.<br /><br />Jerry

 

[antti]

Re: 1971 7.5 Mercury Impeller Stuck

Ah, now that saved a bunch of effort for me too, the Johnson shafts apparently just pull out (and this one didn't). Thanks.<br /><br />I have a 9.8 HP 110 where the impellor was also fused. I ended up using a dremel (actually a chainsaw sharpener) to grind back the impellor hub. Once I got about half way along it loosened up enough to slide off. Did it along the key-way so if I went too far, I hit the key and not the shaft itself.

 

[Johnny Ringo !]

Re: 1971 7.5 Mercury Impeller Stuck

Thanks for the information, hopefully when I get the impeller replaced I'll have a nice little engine.<br /><br />Jerry

I had to chisel one of the other day. I think they put the wrong size one on! I measured the drive shaft top, middle and just above the impeller housing and I got .438 every time. So I ordered a .438, WRONG ! ! The driveshaft was .456 inside the impeller housing, so I reordered a .456 and it came and went one easy. They must have pounded the last one on. I found it easiest to chisel down through the keyway where it is thinner. Now I have something out of alignment and can not get the lower unit back up into my Mercury 7.5 ! Always something.

 

[racerone]

Put a little 4 hp together the other day.----Took minutes.----Did you remove gearcase in neutral ?----If so the gearcase is likely in forward now.------Match the shift lever to the lower unit and slide it together.

 

[merc850]

Put anti-corrosion grease on the shaft where the impeller sits and also on the top splines of the driveshaft and the propeller shaft.

 

[roscoe]

There were a couple years and model that came with driveshafts of different diameters. Make sure you get the right part # impeller.
Serial number is needed to order the part.