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Yes, if it is a Qualified Joint Venture, you can do an 85/15 split.  Leave the current Schedule C on your return, rename it or add your name as a suffix so you can tell them apart.   Then add a 2nd business/Schedule C and make your wife the owner of that one.    You will need to split, according to your agreement, the income and expenses.  

TurboTax will include both Schedule Cs and Schedules SE-T and SE-S (self-employment tax for taxpayer and spouse).   Each Schedule C represents a different business, so if you have vehicle expense or home office expenses, like all other expenses, those have to be split up, so you may need to report the same office or same vehicle on both returns.   Don't duplicate amounts; be careful to ensure you are dividing the expenses and not doubling them.   

• The couple must share net income and deductions in the same proportion as each spouse’s interest in the business. Their respective percentages of the business are determined by the partnership agreement.
• There must be no other partners in the business.
• Both spouses must materially participate in the business.
• Each spouse must include a separate Schedule C reflecting his/her share of the income and deductions on their joint tax return.
• Each spouse must include a separate Schedule SE that shows that spouse’s self-employment income with their joint tax return.
• If the business has employees, then one of the spouses must be designated as the party responsible for reporting and paying employment taxes for those employees.

There’s no formal election required to file as a Qualified Joint Venture. If you qualify as a QJV, you simply include Forms Schedules C and SE with your personal tax return instead of corporate or partnership tax returns. Unless you have employees, there is no need to apply for an Employer Identification Number (EIN).