Ambitious investors with an appetite for risk may be willing to take a bet on stocks other investors wouldn't buy in their wildest dreams. But sometimes, that risk-taking can lead to big gains, whether it's with a company whose future is in question or one that has an uphill battle against competitors. 

We asked three of our contributors which stocks they would recommend for the risk-taking, ambitious investor, and Enviva Partners LP (NYSE:EVA), Boeing Co (NYSE:BA), and 8point3 Energy Partners (NASDAQ: CAFD) rose to the top. Here's a look at why they could be big winners long term. 

Airplane flying above the clouds at dusk.

Image source: Getty Images.

The end might be in sight, but the payouts are huge

Brian Stoffel (Enviva Partners): It's not often that I suggest a stock whose future is in question, but in Enviva Partners I've found one such company. Enviva is a leading worldwide provider of -- of all things -- wood pellets. Northern European energy companies -- burdened with requirements to cut down drastically on greenhouse gas emissions -- are using the pellets as a gap input to make the long-term transition from coal to a combination of solar, wind, and geothermal power.

No one has an infrastructure to match Enviva, with production plants spread throughout the American Southeast and two fully owned deepwater docks in the Ports of Cheasapeake and Wilmington. Management believes that it will be able to pay out $2.36 in dividends this year, which equates to an 8.7% yield at today's prices.

Here's the key to this investment: Enviva's business will be around for a minimum of ten years. At least, that's the basis behind the company's long-term off-take contracts with these international energy companies. As of the last quarterly report, the average contract had 9.8 years left on it, with hefty fees associated with a company backing out of its agreement.

Management has also noted that demand could pick up from Asian energy companies as well in the coming years, led by Japan. That, coupled with any delays in the infrastructure shifts in developed economies, could lengthen Enviva's lifespan markedly.

I don't think this is necessarily a company that investors should "back the truck up" with. There's a cat-and-mouse game that involves investors keeping a close eye on future contracts with the knowledge that a transition to solar or wind could effectively cut long-term business off.

But in the meantime, investors are rewarded with a very hefty dividend. I pledged to buy shares in an earlier piece, but have been prevented from doing so by my broker, which won't allow limited partnerships in my portfolio. As soon as I find a workaround, this, too, will be in my portfolio.

Get high dividends and growth opportunities in one package

Dan Caplinger (Boeing): Most ambitious investors don't pay a lot of attention to dividend stocks, because most dividend payers lack the growth characteristics they crave. But that's not true for Boeing, which has quietly built up its payout to a 3% dividend yield despite having seen its stock soar higher in recent years.

The aerospace industry has benefited from a huge upgrade cycle, with airlines suddenly flush with cash spending wildly on new aircraft from Boeing. The result has been a massive jump in cash flow, and Boeing has responded with impressive increases to its dividends. In less than four years, Boeing has nearly tripled its quarterly dividend payment amount, with its most recent 30% boost coming earlier this year.

For those whose ambitions go beyond dividends, Boeing offers future growth not just from continued innovation on the commercial aerospace side but also with its defense and military applications. The geopolitical picture is getting increasingly cloudy, but one thing that seems likely is that defense spending will tick back upward in the current environment in Washington. That will benefit Boeing and give it a chance to expand on its commercial success. For investors who want to see their portfolios soar, Boeing has already given its longtime shareholders a sneak peek at how a favorable environment could lift the stock ever higher.

An uncertain future for a yieldco leader

Travis Hoium (8point3 Energy Partners): Ambitious investors looking for a big dividend and more potential upside should take a look at 8point3 Energy Partners. The company is a yieldco that buys renewable energy projects from its sponsors, First Solar and SunPower, and then pays cash flows from those projects to investors in the form of a dividend. And that dividend yield now stands at a lofty 7.5%. 

The problem the company has had is that the point of a yieldco is to buy new projects with newly issued debt and equity with the goal of growing the dividend. If the dividend yield is too high the projects won't be accretive to the dividend, making acquisitions unfeasible. And that's the position 8point3 Energy Partners finds itself in today. 

The good news is that the worst case scenario is that investors collect the current dividend for at least the next 20 or so years of existing energy contracts. But if the stock recovers, the company could buy projects and grow the dividend again.

There's also a third option that could lead to a short-term win. First Solar and SunPower are evaluating the best options for their stakes in 8point3 Energy Partners, which could result in a sale of the company. And if a sale takes place at a premium over today's stock price, it could be a quick profit for the ambitious investor.