John McGlynn, who founded the Airlink Group of car parks, said he had wanted to see a “devo max” option on the ballot paper in the historic vote.
In the absence of such an option, he said he had “no choice” but to vote for independence.
Mr McGlynn, who is on the board of Scottish Enterprise, described himself as being a “lifelong Conservative, a person who helped fund the party with donations”.
But he insisted that the referendum is “not about any one political party or any one political leader”, arguing instead: “It’s all about self-determination and whether or not you believe decisions about Scotland’s future are better taken in Scotland or in London.
“It’s about our nation, our tomorrow, our people. It’s about what we can do rather than what others will let us do.
“As a devo max advocate I have come to the conclusion that I have been left with no choice.
“So, in less than 100 hours, I look forward to awaken to the dawning of a new Scotland, a country confident enough in itself to face the next 100 years and beyond as an independent nation.
“I will be voting for a positive future for Scotland; one in which Scots will decide what’s best for them and how to deliver wealth and prosperity for all in Scotland. That’s why I’m voting Yes.”
The businessman said: “As long as two years ago I predicted the absence of devo max on the ballot paper would lead to people - who really wanted devo max - voting for independence, as the status quo was frankly the worst of all options.
“In the last week Better Together, in a last-gasp attempt to kill off independence, has resorted to making promises that look akin to devo max. But it’s too little too late.”
With former prime minister Gordon Brown spearheading the drive for further devolution with an accelerated timetable for new powers to be delivered to Holyrood, Mr McGlynn added: “To add insult to injury this message of jam tomorrow has been delivered by former prime minister Gordon Brown, the man who made the wrong calls on so many big decisions in his time at the Treasury and subsequently inside No. 10 while holding the most powerful office in the land.”
He also hit out at the pro-UK campaign, saying: “They say voting for independence is the biggest risk we could take.
“I would respectfully disagree because their endlessly negative Project Fear has failed. Most Scots - including me - realise the status quo is the worst of all options.”
A spokesman for the Scottish Conservatives said: “As a regular cheerleader for Alex Salmond this comes as no surprise from Mr McGlynn, who has not been a donor or member of the party for three years.”