The fast development and the huge number of existing web services have raised the problem of the urgent need for matchmaking mechanisms. However state-of-the-art matchmakers are unsuitable for locating web services that use different ontologies. This aspect is important since it is not realistic to assume that Web services will always be defined by the same ontology, as the Web service requester and provider operate independently, each defines their own ontologies to describe their services. This is an emergent research issue that has not been well addressed. This work is a contribution to achieve semantic interoperability in a multi-ontology environment. This paper describes a Web service multi-ontology matchmaker for SAWSDL services, called SAWSDL-MOM which locates web services that use different ontologies. The matchmaker engine incorporates a novel partial ontology alignment algorithm with syntax, linguistic and original structural matchers. In determining the 1:1 mappings the Hungarian algorithm is used. Finally a matchmaking strategy is utilized in finding the score of each service. Experimental evaluation and comparison provide strong evidence that SAWSDL-MOM can significantly improve results, achieve better interoperability and scalability.