@Matheus Santz, you are correct!! When using multiple datasources, it is always a best practice to annotate the @Transactional with the TransactionManager reference.
TransactDataSourceConfig.java
package com.spsllc.config;
import javax.sql.DataSource;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import org.springframework.transaction.TransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import com.zaxxer.hikari.HikariDataSource;
@Configuration
@EnableTransactionManagement
public class TransactDataSourceConfig {
    
    @Bean
    @ConfigurationProperties("spsllc.datasource.transactdb")
    public DataSourceProperties transactDataSourceProperties() {
        return new DataSourceProperties();
    }
    @Bean(name = "transactdbDS")
    @ConfigurationProperties("spsllc.datasource.transactdb.configuration")
    public DataSource transactDataSource() {
        return transactDataSourceProperties().initializeDataSourceBuilder().type(HikariDataSource.class).build();
    }
    @Bean
    public JdbcTemplate transactdbJdbcTemplate(@Qualifier("transactdbDS") DataSource dataSource) {
        return new JdbcTemplate(dataSource);
    }
    @Bean
    public NamedParameterJdbcTemplate transactdbNamedParameterJdbcTemplate(@Qualifier("transactdbDS") DataSource dataSource) {
        return new NamedParameterJdbcTemplate(dataSource);
    }
    @Bean(name = "transactTransactionManager")
    public TransactionManager transactTransactionManager() {
        return new DataSourceTransactionManager(transactDataSource());
    }
}
SearchLogRepository.java
package com.spsllc.repository.transactdb;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.namedparam.BeanPropertySqlParameterSource;
import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
import org.springframework.jdbc.support.GeneratedKeyHolder;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;
import com.spsllc.domain.SearchLogEntry;
import lombok.extern.slf4j.Slf4j;
@Repository
@Slf4j
public class SearchLogRepository {
    @Autowired
    @Qualifier("transactdbJdbcTemplate")
    JdbcTemplate jdbcTemplate;
    @Autowired
    @Qualifier("transactdbNamedParameterJdbcTemplate")
    NamedParameterJdbcTemplate nmParamjdbcTemplate;
    @Transactional(transactionManager = "transactTransactionManager")
    public void insert(List<SearchLogEntry> entries) {
        String sql = "INSERT INTO search_log(member_id, weekof_metadata, week_begin_date, " +
                "week_end_date, activity_date,type, name, contact_person, contact_type) " +
                "VALUES(:memberId, :weekofMetadata, :weekBeginDate, " +
                ":weekEndDate, :activityDate, :type, :name, :contactPerson, :contactType);";
        GeneratedKeyHolder generatedKeyHolder = new GeneratedKeyHolder();
        int index = 0;
        for (SearchLogEntry e : entries) {
            nmParamjdbcTemplate.update(sql, new BeanPropertySqlParameterSource(e), generatedKeyHolder,
                    new String[] { "search_log_id" });
            Integer id = generatedKeyHolder.getKey().intValue();
            e.setSearchLogId(id);
            log.info(e.toString());
            index++;
            /** uncomment to test the rollback
            if(index > 5)
                throw new RuntimeException("Testing @Transactional commit/rollback behavior");
             */
        }
    }
}