Mayville Engineering Company, Inc. Schedule 13G discloses that Portolan Capital Management, LLC beneficially owns 1,465,004 shares of common stock of Mayville Engineering Company, Inc. The filing also lists George McCabe as the Manager with identical voting and dispositive power. The reported ownership equals 5.92% of the class as shown on the cover page.
The filing provides the reporting persons' principal business address and CUSIP 578605107, and is signed by George McCabe with a signature date of 05/28/2026.
Positive
None.
Negative
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Insights
Portolan reports a 5.92% beneficial stake via its manager, George McCabe.
The filing is a routine Schedule 13G disclosure showing 1,465,004 shares held by Portolan Capital Management, LLC with sole voting and dispositive power stated in the cover rows. The record includes the reporting entity's address and the issuer CUSIP 578605107.
Holding size is stated as 5.92%; timing and cash‑flow treatment are not described beyond the signature date 05/28/2026. Subsequent filings would show any change in position.
Filing attributes ownership to an investment manager and its manager as an indirect holder.
The statement clarifies that Portolan acts as investment manager for various clients and that Mr. McCabe holds indirect beneficial ownership through his managerial role. Item 6 notes no other single person's interest exceeds five percent among underlying clients.
Disclosure aligns with passive/beneficial‑owner reporting practice; the filing does not claim activist intent or changes to prior holdings.
Key Figures
Shares beneficially owned:1,465,004 sharesPercent of class:5.92%CUSIP:578605107+1 more
4 metrics
Shares beneficially owned1,465,004 sharescover page figures for Portolan Capital Management, LLC
Percent of class5.92%Row 11 on the cover page
CUSIP578605107Issuer common stock CUSIP on cover page
Signature date05/28/2026Signed by George McCabe
Key Terms
Schedule 13G, beneficially owned, sole dispositive power, sole voting power
4 terms
Schedule 13Gregulatory
"Item 1. (a) Name of issuer: Mayville Engineering Company, Inc."
A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.
beneficially ownedfinancial
"This statement is being filed with respect to the shares ... beneficially owned directly by Portolan Capital Management, LLC"
Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.
sole dispositive powerfinancial
"7 | Sole Dispositive Power 1,465,004.00"
Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.
sole voting powerfinancial
"5 | Sole Voting Power 1,465,004.00"
Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
Mayville Engineering Company, Inc.
(Name of Issuer)
Common stock, no par value
(Title of Class of Securities)
578605107
(CUSIP Number)
05/20/2026
(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
Rule 13d-1(b)
Rule 13d-1(c)
Rule 13d-1(d)
schemaVersion:
SCHEDULE 13G
CUSIP Number(s):
578605107
1
Names of Reporting Persons
Portolan Capital Management, LLC
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
1,465,004.00
6
Shared Voting Power
0.00
7
Sole Dispositive Power
1,465,004.00
8
Shared Dispositive Power
0.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
1,465,004.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
5.92 %
12
Type of Reporting Person (See Instructions)
IA
SCHEDULE 13G
CUSIP Number(s):
578605107
1
Names of Reporting Persons
George McCabe
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
UNITED STATES
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
1,465,004.00
6
Shared Voting Power
0.00
7
Sole Dispositive Power
1,465,004.00
8
Shared Dispositive Power
0.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
1,465,004.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
5.92 %
12
Type of Reporting Person (See Instructions)
IN
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
Mayville Engineering Company, Inc.
(b)
Address of issuer's principal executive offices:
135 S. 84th Street, Suite 300, Milwaukee, WI, 53214
Item 2.
(a)
Name of person filing:
This statement is being filed with respect to the shares Common Stock of the Issuer beneficially owned (1) directly by Portolan Capital Management, LLC, a registered investment adviser, in its capacity as investment manager for various clients, and (2) indirectly by George McCabe, the Manager of Portolan Capital Management, LLC. Portolan Capital Management, LLC and Mr. McCabe are sometimes individually referred to herein as a "Reporting Person" and collectively as the "Reporting Persons."
(b)
Address or principal business office or, if none, residence:
The address of the principal business office of each of the Reporting Persons is 2 International Place, FL 26, Boston, MA 02110.
(c)
Citizenship:
Portolan Capital Management, LLC - DE
Mr. McCabe - USA
(d)
Title of class of securities:
Common stock, no par value
(e)
CUSIP Number(s):
578605107
Item 3.
If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)
An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)
An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)
A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)
A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
(k)
Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.
Ownership
(a)
Amount beneficially owned:
The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated by reference herein.
(b)
Percent of class:
The information required by Item 4(b) is set forth in Row 11 of the cover page for each of the Reporting Persons and is incorporated by reference herein.
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
The information required by Item 4(c) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated by reference herein.
(ii) Shared power to vote or to direct the vote:
0
(iii) Sole power to dispose or to direct the disposition of:
The information required by Item 4(c) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated by reference herein.
(iv) Shared power to dispose or to direct the disposition of:
0
Item 5.
Ownership of 5 Percent or Less of a Class.
Not Applicable
Item 6.
Ownership of more than 5 Percent on Behalf of Another Person.
If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required.
Various persons have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the Common Stock of Mayville Engineering Company, Inc. No one person's interest in the Common Stock of Mayville Engineering Company, Inc. is more than five percent of the total outstanding Common Stock.
Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
Not Applicable
Item 8.
Identification and Classification of Members of the Group.
Not Applicable
Item 9.
Notice of Dissolution of Group.
Not Applicable
Item 10.
Certifications:
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.
SIGNATURE
After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.
What stake does Portolan Capital report in Mayville Engineering (MEC)?
Portolan Capital Management reports beneficial ownership of 1,465,004 shares, representing 5.92% of Mayville Engineering's common stock as stated on the cover page. The disclosure attributes sole voting and dispositive power to Portolan.
Who is listed as the reporting person for the MEC Schedule 13G?
The filing lists Portolan Capital Management, LLC as the reporting entity and George McCabe as Manager. Portolan is identified as a Delaware entity and Mr. McCabe as a U.S. citizen with managerial authority over the reported shares.
Does the Schedule 13G say Portolan acts for specific clients?
Yes. The statement says Portolan holds the shares in its capacity as investment manager for various clients. Item 6 notes that no single client's interest exceeds five percent of the class, per the filing language.
What voting and dispositive powers are reported for the MEC shares?
The cover rows show sole voting power of 1,465,004 shares and sole dispositive power of 1,465,004 shares for Portolan Capital Management, LLC, with 0 shared voting or dispositive power listed.
When was the Schedule 13G for MEC signed and what CUSIP is shown?
The filing bears signatures by George McCabe with a signature date of 05/28/2026, and lists CUSIP 578605107 for the issuer's common stock class on the cover page.
