miller19j
Leo
  
Solvang
Posts: 1,888
APPD 0.22
Post Rank: 34
Boat with an Engine Cover
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Posted: Jan. 22 2003,10:22 am |
Post # 1 |
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I thought that I would share with you what I learned about rebuilding my
jet in case you decide to do yours.
First of all don’t buy a Berkley factory tuned impeller! The claims
about balancing and tuning they make are false. It is basically an
impeller that they have someone hit it with a flap wheel and spray some
paint on.
I found that mine was .005 out of round and .002 off on the front
surface and the wear ring was .003 undersized from what was advertised.
. This doesn’t seem like much until you start to do a tolerance stack
up. The clearance of the wear ring is about .015 per side and the bowl
bearings have .003 slop in them so if you add up all the potential you
could have a clearance between your impeller and wear ring of .004. An
average piece of paper is .002 thick so that would be the clearance of
two sheets of paper.
The next thing that I found that was off was the clearance between the
front surface of the impeller and the suction piece. I have been told by
jet rebuilders that this is the most critical dimension. It should be
.025- .030 mine was .150 that is incredibly off!
(set up in the lathe for measuring)
So some second machining is required! If you just buy the parts and
bolt them together you won’t have good results.
All of these are easy to set if you have access to a lathe and some good
measuring tools. I would recommend buying a standard impeller setting
the tolerances and cleaning it up with a flap wheel and balancing it.
Then use the money you saved to have the part reanodized when you are
done. If you do not have access to a Lathe you can have a Machine Shop do it for you I would be surprised if the work cost you more than $50. Make sure that they set the clearances with the impeller in the shaft as shown in the picture below.
(Truing up wear ring and setting clearances)
You will also need access to a press to press on a new main bearing and
seal sleeve (a machines shop could do this if you don’t have a press). I
made a few pieces of tooling to drive the bowl bearings in and some of
the seals but you could do it with a punch if you are careful. The impeller nut it 1 13/16 you will probably need to remove it with a deep socket and impact wrench because they are usually frozen on. I made mine out of a cheap socket from harbor freight, some steel pipe, and a few welds. It cost me less than $5 in parts. I would bet that you could also rent one from a tool rental place as well.
I did some flowing of my bowl to improve flow. I broke down the trailing
edges of the vanes with a carbide burr in a die grinder and then used a
flap wheel to polish the veins as far in the bowl as I could reach.
After that I had the bowl powder coated. The resulting surface is
incredibly smooth.
In general the pump rebuilding is pretty simple if you have access to
some machine tools you can make it just as good or better that it would
come from any pump rebuilder. If you buy the basic rebuild parts it
would cost you about $300 this would give you every seal, bearing, new
impeller, new wear wring, and gaskets. Basically a new jet. If your impeller is serviceable it would be about $150 less. Add about $150 for powder coating (if you want to go that route) and your time and you are set.
Sorry for the novel but I hate to see people spend good money to have
something done that they could do themselves.
I would recommend Buying the book “Marine Jet Drive” you can get it at amozon.com and it will walk you through the basics of jet pump rebuilding.
Hey Sleek Bite Me!
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