Elon Musk has a lot riding on his plan to merge Tesla Motors Inc. with SolarCity Corp. -- including a big chunk of his $8.3 billion fortune.

He may be better off just giving up on the debt-ridden solar-panel installer and focusing on turning Tesla into a profitable enterprise. But Musk has a long history of throwing his money after his grand visions, like weaning the world off fossil fuels and colonizing Mars, sometimes running very low on cash and coming close, by his own admission, to personal bankruptcy.

“He’s got guts, I’ll give him that,” said Ross Gerber, chief executive officer of Gerber Kawasaki Wealth & Investment Management, which has a $5 million position in Tesla and has recently been selling shares. “He really pushes it out on his companies, but Elon could implode.”

As it is, only about 4 percent of his net worth is tied up in SolarCity, of which he’s the chairman and largest shareholder. The company has been burning cash at a prodigious rate and, according to regulatory filings, is getting closer to defaulting on its $3 billion in debt. If the proposed acquisition by Tesla doesn’t come to pass, and SolarCity burns out, Musk will take a relatively minor hit.

He suffered one Thursday, when his fortune, on paper, shrank by $779 million, according to the Bloomberg Billionaires Index. That was due to two factors: drops in the companies’ stock prices; and Wednesday’s regulatory filing showing he has put up an additional $489 million of his Tesla and SolarCity stock as collateral to secure personal borrowings. The pledged shares are stripped out of his total net worth calculation because they’re not immediately available to him. The borrowing is for personal liquidity; he doesn’t even accept the $37,584 minimum-wage salary Tesla is required to pay him.

The bigger threat to Musk’s bank accounts would come from SolarCity dragging down Tesla in a combined company. He has half of his money in the electric-car maker, of which he is CEO; about 46 percent of his value is in his closely held rocket-launch company Space Exploration Technologies Corp. (SpaceX, as its known, suffered a setback Thursday when its Falcon 9 rocket burned up on a launch pad, destroying itself and an Israeli communication satellite.)

Though the prospect of a merger has been controversial -- with some analysts and investors viewing it as a costly bailout of SolarCity -- Musk has said he is as committed as ever to seeing it through. He’s said customers will benefit from one-stop shopping and installation of solar panels, energy storage and electric-car charging. Many shareholders are behind him.

“A lot of the longer-term investors, while they aren’t extremely enthusiastic about the SolarCity deal, still stand by Elon and what he’s trying to achieve,” said Ben Kallo, an analyst with Robert W. Baird & Co. “Typically investors like to be paired with management teams that have big stakes in their companies.”

Tesla made a bid to acquire SolarCity in June, and a two-person committee of the SolarCity board approved the all-stock offer, now valued at $2.3 billion. The Securities and Exchange Committee must review documents related to the offer that shareholders will receive, to ensure there’s adequate disclosure and general compliance with securities laws. Then the matter will be put to a vote by shareholders of both companies.

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