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gcarter
05-31-2004, 07:33 PM
My '86 Minx has the original Alpha drive w/integral water pump.
My plan entails removing the drive pump and replaceing it witha engine driven seawater pump and a transom water pickup.
My problem is the shaft driving the pump impellor has a "chord" type key to drive the impellor. This key is approx 1.13 long X .44 wide X .13 chord thickness and weighs < .25 oz or <5 gr (the minimum of my wife's cooking scale). If I had to guess, I'd say about 1/2 of those.
Now I'd like to ditch the key but I'm concerned about balance. One alternative woulod be to cut down the old impellor to th e fiberglass core and "glue" it and the key to the shaft.
Oh yeah, the shaft diameter is .875".
I haven't done any engineering for 17 years or about the time I started my business. I need some help! :redface:
Photo #2 is the lower unit shaft with the flat and photo #1 is the key.
Please help;
George

BUIZILLA
05-31-2004, 08:18 PM
George, your balance concern is a non-issue. Don't worry about it.

J

pmreed
05-31-2004, 08:27 PM
George,
If you're looking for concensus, BUIZILLA is exactly right. You are talking an about a practically insignificant mass with a lever arm of less than 1/2 inch. It wouldn't bother you at 10K RPM, much less the 3 or 4K rpm the shaft'll be turning at WOT.

Phil

Greg
05-31-2004, 08:39 PM
I am considering on doing the same on my Alpha someday. I heard somewhere that the Alpha uses the cool water passing through it for inner cooling and also that some people leave the impeller in and use it to power a drive shower. Or am I just all wet?

gcarter
05-31-2004, 08:50 PM
Greg, I'm leaving everything open. Water will still circulate through the drive as it currently does, just no impellor. I'm also useing a drive shower. Additionally, I've made a water hose blocking plate for the gimbal housing, similar to the exhaust blocking plate. There will be no water hose.
Thanks Jim and Phill, I appreciate your input. Makes my job a lot easier.

George :biggrin:

mphatc
05-31-2004, 08:50 PM
While were discussing your lower unit :umbrella: what did you use for paint on that? It shines deeper than new!


Mario

MOP
05-31-2004, 08:52 PM
Very true is does help to cool the drive, capping the flow is the wrong thing to do. I have posted on taking the water and running out onto the upper cap, a bilge pump fitting put just above the drive does the trick gives you a free drive shower with none of the is there or is there not drag from a shower pickups. Under way you would be very surprised just how much water is forced through from the drives intakes.

gcarter
05-31-2004, 09:08 PM
Thanks Mario, that was a lot of work.
Several months ago I asked how to cosmetically restore my drive, and Rootsy explained the process. There is a thread I started on the subject.
Anyway I took it to bare metal, primed it with R-M EP789 epoxy primer, which has a lot of zinc chromate in it, filled and sanded it smooth. I finished sanded the primer with 800 wet. Before stripping my drive looked like a cow patty, and was badly coroded.
The paint is R-M UNO-HD ebony black. This paint has so much solids in it, it doesn't look like a part painted with shiny paint. Instead it looks like a part molded in a solid plastic of a particular color. The lower is as it was sprayed, no rubbing.

George