<PAGE>
                                                                   Exhibit 10.5


                REVOLVING LINE OF CREDIT MASTER PROMISSORY NOTE

$7,000,000.00                                                    August 15, 2002

     FOR VALUE RECEIVED, the undersigned, BANKERS INSURANCE GROUP, INC. a
Florida corporation (herein, "BIG") and BANKERS UNDERWRITERS, INC., a Florida
corporation (herein, "BUI") (BIG and BUI herein, collectively, "Debtor") jointly
and severally promise to pay to the order of INSURANCE MANAGEMENT SOLUTIONS
GROUP, INC., a Florida corporation, together with any other holder hereof
(herein, "Holder"), the principal sum of Seven Million and No/100 dollars
($7,000,000.00), together with interest thereon from the date hereon at a rate
equal to ten and 75/100 percent (10.75%) per anum, both principal and interest
being payable at Holder's place of business, 360 Central Avenue, St. Petersburg,
Florida 33701, or at such other places as Holder may designate from time to
time, in the following manner:

       Commencing on the first day of September 2002, all accrued and unpaid
       interest shall be due and payable, which shall also be paid on the first
       day of each calendar month thereafter (herein, "Payment Date"). All
       unpaid principal and interest shall be due and payable in full on the
       earlier of: (i) July 31st, 2003; or (ii) the date exactly ninety (90)
       days (or the next business day thereafter) following receipt by Debtor
       of written notice from Holder demanding repayment in full of this Note
       (a "Demand"), which Demand can only be made by Holder at any time
       following the occurrence of a Demand Event (as that term is defined
       below).

For purposes of this Note:

(a)  the term "Demand Event" shall mean:

     (i)   the expiration of an Offer (as that term is defined in the Merger
     Agreement) without any Shares (as that term is defined in the Merger
     Agreement) owned by Public Shareholders (as that term is defined in the
     Merger Agreement) being purchased pursuant to the Offer;

     (ii)  if the Holder shall not have then purchased Shares owned by the
     Public Shareholders pursuant to an Offer, the later of: (A) December 31,
     2002 or (B) such later date on which the Offer is terminated by Holder if
     the Offer is extended beyond December 31, 2002 by Holder;

     (iii) the date of any breach of the Merger Agreement by Debtor or its
     Affiliates;

     (iv)  the date of the termination or expiration of the Merger Agreement.

(b)  the term "Merger Agreement" shall mean that certain Agreement and Plan of
Merger by and Among BIG, Bankers Insurance Company ("BIC"), Bankers Security
Insurance Company ("BSIC"), Bankers Management Corporation and the Holder of
even date herewith.

Events of Default. The above notwithstanding, all principal and accrued but
unpaid interest shall become immediately due and payable by Debtor in any of
the following events:


<PAGE>
     (i)       An uncured default by Debtor under this Note or the Credit and
Security Agreement of even date herewith (the "Credit Agreement");

     (ii)      An uncured default by Debtor under that certain Collateral
Assignment of Flood Book of even date herewith (the "Collateral Assignment"); or

     (iii)     An uncured default by BIG, BIC or BSIC under the Merger
Agreement.

Credit and Security Agreement.  Unless the context shall otherwise require,
capitalized terms not defined herein shall have the meanings assigned thereto in
the Credit Agreement.

Master Note.  This Note is a master note, and it is contemplated that any
amounts evidenced hereby will be advanced from time to time to the Debtor by
Holder in installments, as requested from time to time by the Debtor to the
Holder.

Advances.  It is further contemplated that any amounts advanced under this Note
may be prepaid from time to time by the Debtor. Debtor may receive advances
hereunder at any time, up to a maximum aggregate amount outstanding at any one
time equal to the principal amount of this Note, provided that: (i) Debtor is
not in default under any provision of this Note, the Credit Agreement, or any
other documents executed in connection with this Note or the Credit Agreement,
or any other note or other loan documents now or hereafter executed in
connection with any other obligation of Debtor to Holder; (ii) Debtor is not in
default with respect to its obligations under that certain Collateral
Assignment; and (iii) neither Debtor, BIC, nor BSIC is in default with respect
to their obligations under the Merger Agreement. By reason of such prepayments
hereon there may be times when no indebtedness is owing hereunder, and
notwithstanding any such occurrence, this Note shall remain valid and shall be
in full force and effect as to each subsequent principal advance made hereunder.
Each principal advance and each payment made pursuant to this Note shall be
reflected by notations made by Holder on the grid attached hereto as Schedule
"A", and Holder is hereby authorized to record on such grid all such principal
advances and payments. The aggregate unpaid amounts reflected by the notations
made by Holder on the attached grid shall be deemed rebuttably presumptive
evidence of the principal amount remaining outstanding and unpaid on this Note.
No failure of Holder so to record any advance or payment shall limit or
otherwise affect the obligation of the Debtor hereunder with respect to any
advance, and no payment of principal by the Debtor shall be affected by the
failure of Holder so to record the same.

Advance Obligations.  All advances to be made hereunder shall be made at the
option of Debtor, by providing written notice to Holder of the amount of a
proposed advance. This Note shall be valid and enforceable as to the aggregate
amount advanced at any time hereunder, whether or not the full face amount
hereof is advanced.

Application of Payments.  Each payment on the indebtedness evidenced hereby will
first reduce charges related to this Note owed by the Debtor that are neither
principal nor interest. The remainder of each such payment will be applied first
to the interest then accrued on said principal sum remaining unpaid, and then to
the reduction of such unpaid principal. Principal and interest shall be payable
in lawful money of the United States of America.

--------------------------------------------------------------------------------


                                     2 of 7

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Prepayment. The Debtor hereof shall not incur any penalty upon the prepayment
of all or any part of the indebtedness evidenced hereby.

Interest Calculation. Interest shall be calculated on all amounts advanced
based on the actual number of days said amounts are outstanding. Interest shall
be computed on the basis of a year of actual number of days per year [i.e.
three-hundred-sixty-five (365) days] and charged for the actual number of days
in the payment period.

Maximum Rate. Debtor shall have no obligation to pay interest or payments in the
nature of interest in excess of the maximum rate of interest allowed to be
contracted for by law, as changed from time to time, applicable to this Note
(herein, "Maximum Rate"). Any interest in excess of the Maximum Rate paid by
Debtor (herein, "Excess Sum") shall be credited as a payment of principal, or,
if Debtor so requests in writing, returned to Debtor, or, if the indebtedness
and other obligations evidenced by this Note have been paid in full, returned to
Debtor together with interest at the same rate as was paid by Debtor during such
period. Any Excess Sum credited to principal shall be credited as of the date
paid to Holder. Holder may, without such action constituting a breach of any
obligations to Debtor, seek judicial determination of the applicable rate of
interest, and its obligation to pay or credit any proposed Excess Sum to Debtor.

Collateral. The obligations under this Note and the Collateral Assignment are
secured by and subject to the terms and conditions of the Credit Agreement and
various other loan documents of even date herewith executed by and between
Debtor and Holder, respectively.

Past Due. Time is of the essence hereunder. If any payment hereby required is
overdue for more than five (5) days, the Holder of this Note may, at its
option, and without notice, declare the entire balance of principal then
remaining unpaid to be immediately due and payable, and any failure to exercise
said option shall not constitute a waiver of the right to exercise the same at
any other time. Further, upon an Event of Default, Holder of this Note may, at
its option, and without notice, adjust the interest due on the aggregate
principal amount remaining due and unpaid, together with accrued interest,
upward, to the rate of eighteen (18.0%) per centum per annum, or the Maximum
Rate of interest permitted by law, whichever rate shall be the lesser, which
rate of interest, as adjusted upward, shall be paid on all sums due hereunder
until the said sums have been paid in full, regardless of any payments made by
the maker hereof, and accepted by the Holder, after said option has been
exercised. Upon default in making any payment hereby required, Debtor promises
to pay all costs and expenses, including reasonable attorney's fees (including
the cost of any appeals), incurred in collecting this Note by legal proceedings
or through an attorney.

Remedies. The remedies of Holder herein and in the Credit and Security
Agreement shall be cumulative and concurrent, and may be pursued singularly,
successively, or together, at the sole discretion of Holder, and may be
exercised as often as occasion therefor shall arise. No action or omission of
Holder, including specifically any failure to exercise or forbearance in the
exercise of any remedy, shall be deemed to be a waiver or release of the same,
such waiver or release to be effected only through a written document executed
by Holder and then only to the extent specifically recited therein. A waiver or
release with reference to any one event shall not be construed as continuing or
as constituting a course of dealing, nor shall it be construed as a bar to, or
as a waiver or release of, any subsequent remedy as to a subsequent event.

                                     3 of 7
<PAGE>
Set-Off. In addition to all liens upon, and rights of set-off against, any
monies, securities, or other property of any of the Debtor given to Holder by
law, Holder shall have a lien upon and a right of set-off against all monies,
securities and other property of any of the Debtor now or hereafter in the
possession of, or on deposit with, Holder, whether held in a general or special
account or deposit, for safekeeping, in trust or otherwise, and every such lien
and right of set-off as may be exercised without demand upon or notice to any
Debtor, and the Holder shall have no liability with respect to any of Debtor's
checks or other items which may be returned or other funds transfers which may
not be made due to insufficient funds thereafter.

Exercise/Modification. Neither any failure nor any delay on the part of Holder
in exercising any right, power, or privilege under this Note shall operate as a
waiver thereof, nor shall a single or partial exercise thereof preclude any
other or further exercise or the exercise of any other right, power, or
privilege. No modification, amendment, or waiver of any provisions of this Note
shall be effective unless in writing and signed by a duly authorized officer of
Holder, and then the same shall be effective only in the specific instance and
for the purpose for which given. No notice to, or demand on, any Debtor in any
case shall entitle any Debtor to any other or further notice or demand in the
same, similar, or other circumstances.

Severability. Any provision of this Note which is prohibited or unenforceable in
any jurisdiction shall, as to such jurisdiction, be ineffective to the extent of
such prohibition or unenforceability without invalidating the remaining
provisions hereof or affecting the validity or enforceability of such provision
in any other jurisdiction.

Waiver. Debtor and any other person liable for the payment hereof respectively,
hereby expressly waive any valuation and appraisal, presentment, demand for
payment, notice of dishonor, protest, notice of nonpayment or protest, all other
forms of notice whatsoever, except as set forth herein, and diligence in
collection.

No Waiver. Acceptance of payments marked "payment in full" or "in satisfaction"
or words to similar effect shall not affect the duty of Debtor to pay all
obligations due hereunder, and shall not affect the right of Holder to pursue
all remedies available to it hereunder or under any other agreement between the
Debtor hereof and the Holder, including but not limited to that certain Credit
and Security Agreement of even date herewith.

Jury Trial. DEBTOR AND ANY OTHER PERSON LIABLE FOR PAYMENT HEREOF, BY EXECUTING
THIS NOTE OR ANY OTHER DOCUMENT CREATING SUCH LIABILITY, WAIVE THEIR RIGHTS TO A
TRIAL BY JURY IN ANY ACTION, WHETHER ARISING IN CONTRACT OR TORT, BY STATUTE OR
OTHERWISE, IN ANY WAY RELATED TO THIS NOTE. THIS PROVISION IS A MATERIAL
INDUCEMENT FOR HOLDER'S EXTENDING CREDIT TO DEBTOR AND NO WAIVER OR LIMITATION
OF HOLDER'S RIGHTS UNDER THIS PARAGRAPH SHALL BE EFFECTIVE UNLESS IN WRITING AND
MANUALLY SIGNED ON HOLDER'S BEHALF.

Jury Trial Consideration. Debtor acknowledge that the above paragraph has been
expressly bargained for by Holder as part of the loan evidenced hereby and that,
but for Debtor's agreement and the agreement of any other person liable for
payment hereof thereto, Holder would not have extended the loan for the term and
with the interest rate provided herein.

                                     4 of 7
<PAGE>
Binding. The provisions of this Notes shall be binding upon the heirs,
successors, and assigns of Debtor, except that Debtor may not assign or
transfer its obligation hereunder without the written consent of Holder, and
shall inure to the benefit of Holder, its successors, and assigns.

Governing Law. This Note is to be governed by and construed under the laws of,
the State of Florida, without regard to choice of law provisions as amended,
except as modified by the laws and regulations of the United States of America.

Venue. Debtor hereby consents and submits to the jurisdiction of the courts of
the State of Florida, and, notwithstanding his, her, their, or its place of
residence or organization or the place of execution of this Note, any
litigation relating hereto, whether arising in contract or tort, by statute or
otherwise, shall be brought in (and, if brought elsewhere, may be transferred
to) a State court of competent jurisdiction in Pinellas County, Florida.

Paragraph Headings; Gender and Number. The headings inserted at the beginning
of each paragraph are for convenience of reference only and shall not limit or
otherwise affect or be used in the construction of any of the terms or
provisions hereof. The plural shall include the singular and the singular, the
plural, wherever the context so admits. The masculine shall include the
feminine and the neuter; the feminine, the masculine and the neuter; and the
neuter, the masculine and the feminine.

Documentary Stamp. This instrument was made, executed and delivered outside the
State of Florida, and no Florida Documentary Stamp Tax is due hereon in
accordance with F.A.C. 12B-4.053(33).

Notices. Any and all notices, designations, consents, offers, acceptances, or
any other communication provided for herein shall be given in writing by hand
delivery, by overnight carrier, by registered or certified mail or by facsimile
transmission and shall be addressed as follows:

          As to Borrower:          Bankers Insurance Group, Inc.
                                   360 Central Avenue, 17th Floor
                                   St. Petersburg, Florida 33701
                                   Att: David B. Snyder
                                   Telephone: (727) 823-4000
                                   Telefax: (727) 823-6518

                                   and

                                   Bankers Underwriters, Inc.
                                   360 Central Avenue, 17th Floor
                                   St. Petersburg, Florida 33701
                                   Att: David B. Snyder
                                   Telephone: (727) 823-4000
                                   Telefax: (727) 823-6518

          As to Lender:            Insurance Management Solutions Group, Inc.
                                   360 Central Avenue, 16th Floor
                                   St. Petersburg, Florida 33701
                                   Att: David Howard, President
                                   Tel#: (727) 803-2040
                                   Fax: (727) 803-4093


                                     5 of 7
<PAGE>
     IN WITNESS WHEREOF, Debtor has caused this Note to be signed, sealed and
delivered in its name on the day and year first above written.


                                        DEBTOR:


                                        BANKERS INSURANCE GROUP, INC.
                                        a Florida corporation


                                        By: /s/ David B. Snyder
                                            -----------------------------
                                                  Its Vice President &
                                                      Assistant Secretary
                                                  (CORPORATE SEAL)


                                        and


                                        BANKERS UNDERWRITERS, INC.
                                        a Florida corporation


                                        By: /s/ David B. Snyder
                                            -----------------------------
                                                  Its Vice President &
                                                      Assistant Secretary
                                                  (CORPORATE SEAL)


                                     6 of 7
<PAGE>
                                  SCHEDULE "A"
                             MASTER PROMISSORY NOTE

                            Debtor: Bankers Insurance Group, Inc. and
                                    Bankers Underwriters, Inc.

                            Holder: Insurance Management Solutions Group, Inc.

                      Project Name: Revolving Line of Credit

                   Original Amount: $7,000,000.00

                             As of: 8/15/02

<Table>
<Caption>
                                                                           AMOUNT                                     NET
        MONTH                                AMOUNT                  OF PRINCIPAL          OUTSTANDING          AVAILABLE
       ENDING                           OF ADVANCES                     REPAYMENT              BALANCE             AMOUNT
--------------------------------------------------------------------------------------------------------------------------
<S>                               <C>                              <C>                <C>                <C>
Original Amount                                                                        $7,000,000.00      $7,000,000.00
                                   $0.00                            $0.00              $7,000,000.00              $0.00
                                   $0.00                            $0.00              $7,000,000.00              $0.00
                                   $0.00                            $0.00              $7,000,000.00              $0.00
                                   $0.00                            $0.00              $7,000,000.00              $0.00
                                   $0.00                            $0.00              $7,000,000.00              $0.00
                                   $0.00                            $0.00              $7,000,000.00              $0.00
                                   $0.00                            $0.00              $7,000,000.00              $0.00
                                   $0.00                            $0.00              $7,000,000.00              $0.00
                                   $0.00                            $0.00              $7,000,000.00              $0.00
                                   $0.00                            $0.00              $7,000,000.00              $0.00
                                   $0.00                            $0.00              $7,000,000.00              $0.00
                                   $0.00                            $0.00              $7,000,000.00              $0.00
                                   $0.00                            $0.00              $7,000,000.00              $0.00
</TABLE>









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