470 impeller, new style, won't tighten

[natemoore]

I was putting the impeller back on today when I started having self-doubts about it touching the front cover on the back side, so I took the impeller off again to get another look at the backside of the impeller and the inside cover.

Then I noticed some aluminum powder on the threads. Apparently, I misthreaded the impeller even though I started it by hand and it went on straight.

Now I can hand tighten it all the way on without the torque wrench.

1) Does this impeller rely on tapered threads to keep it tight on the stud?

2) This is a $70 part. What do you think about the idea of me using a large round punch to slightly bend the last three threads of the impeller to create some friction, then using Loctite 271 (red) for added measure?

The manual says use no Loctite on the impeller, but I'll worry about that if/when I ever have to take it off again.

The manual also specifies 15 lb-ft of torque, so apparently it doesn't take much to keep the impeller snug on the stud.

 

[natemoore]

Re: 470 impeller, new style, won't tighten

Upon closer inspection, it looks like the impeller will bottom out on the camshaft before it hits the front cover, and the LH thread will keep it tight, so I guess I've answered my own question.

However, the impeller was hard to get off the stud to begin with, and it was equally snug putting it back on, I assumed it had tapered threads and the torque setting of 15 lbs-ft would set it at the correct height on the stud....which sounded screwy to me....but it's a Mercruiser.