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                                                                     EXHIBIT 5.1
 
                  [Letterhead of Fulbright & Jaworski L.L.P.]
 
   
April 23, 1998
    
 
EVI, Inc.
5 Post Oak Park, Suite 1760
Houston, Texas 77027-3415
 
Ladies and Gentlemen:
 
   
     We have acted as counsel for EVI, Inc., a Delaware corporation (the
"Company"), in connection with the registration under the Securities Act of 1933
(the "Act") of up to 50,200,112 shares (the "Shares") of the Company's common
stock, $1.00 par value, pursuant to a Registration Statement on Form S-4 (the
"Registration Statement") filed by the Company with the Securities and Exchange
Commission. The Shares are to be issued in connection with the proposed merger
(the "Merger") of Weatherford Enterra, Inc., a Delaware corporation
("Weatherford"), with and into the Company pursuant to an Agreement and Plan of
Merger dated as of March 4, 1998, as amended by Amendment No. 1 dated April 17,
1998, and Amendment No. 2 dated April 22, 1998 (the "Merger Agreement"), by and
between the Company and Weatherford.
    
 
     In connection therewith, we have examined originals or copies certified or
otherwise identified to our satisfaction of the Registration Statement, the
Merger Agreement, the Restated Certificate of Incorporation of the Company, the
By-laws of the Company, the corporate proceedings with respect to the Merger and
the proposed issuance of the Shares and such other documents and instruments as
we have deemed necessary or appropriate for the expression of the opinions
contained herein.
 
     We have assumed the authenticity and completeness of all records,
certificates and other instruments submitted to us as originals, the conformity
to original documents of all records, certificates and other instruments
submitted to us as copies, the authenticity and completeness of the originals of
those records, certificates and other instruments submitted to us as copies and
the correctness of all statements of fact contained in all records, certificates
and other instruments that we have examined.
 
     Based on the foregoing, and having regard for such legal considerations as
we have deemed relevant, we are of the opinion that the Shares proposed to be
issued by the Company in connection with the Merger have been duly authorized
for issuance and, when issued in accordance with the terms of the Merger
Agreement, will be validly issued, fully paid and nonassessable.
 
     The foregoing opinion is limited to the federal laws of the United States
of America and the General Corporation Law of the State of Delaware, and we are
expressing no opinion as to the effect of the laws of any other jurisdiction.
 
   
     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to our firm under the caption "Legal
Matters" in the Joint Proxy Statement/Prospectus contained in the Registration
Statement.
    
 
                                            Very truly yours,
 
                                            
                                            By:  /s/ FULBRIGHT & JAWORSKI L.L.P.
                                              ----------------------------------
                                              Fulbright & Jaworski L.L.P.