Mr Harris, a livestock buyer and seller, discovered what a mess his finances were in only after Bourton had left the country and Westpac bank tried to sell his home by mortgagee auction.
He thought he and his partner had only a $265,000 loan on the home they had bought together in River Rd.
"Our accounts were all over the place and we had no idea what was going on and we had to do something."
Crown prosecutor Rebecca Mann took Mr Harris through dozens of transactions allegedly made by Bourton across his four accounts, including that she had created two home loans totalling $314,000 in the name of Mr Harris' family trust.
The Crown claims Bourton used $98,000 to settle her own purchase of a commercial property in Lake Rd, which almost fell through because she had insufficient.
Ms Mann asked Mr Harris if he consented to Bourton using $29,700 from his cheque account as a deposit on the property. He said he did not.
Mr Harris said he did not discover the alleged fraud until 2007, when a Westpac representative told him the bank intended to sell the River Rd property.
At that time, he was in regular phone contact with Bourton who had moved to Ireland and he asked her about the outstanding money, which he claims she indicated to be around $750,000.
"She kept saying she would sort it out and, as we all know, nothing ever got sorted out."
He and his partner laid a complaint with police in December 2007 and Bourton was arrested in 2009 when she returned from Ireland.
In cross-examination, Bourton's lawyer John Watson questioned Mr Harris over his friendship with the Bourton family and suggested he had been intimate with Bourton, which was denied.
Mr Harris was further questioned over his income tax returns, some of which he admitted had not been filed.
Mr Watson also suggested that Mr Harris was completely aware of what he was signing when he authorised a $100,000 home loan the Crown claims he was tricked into authorising.
During Mr Harris' evidence, Bourton often shook her head and made notes.
The trial in front of Judge Philip Connell is set down for three weeks.