Marley and Scrooge were business partners. They are described as having been like "two kindred spirits." The implication here is that Marley, like Scrooge, was a coldly pragmatic, unfeeling, unkind man, concerned only with money and profit. In this way, Scrooge and Marley were alike, or "kindred," and so we might infer that they got along rather well.
A little later in the story, we are told that since Marley died, seven years previously, Scrooge had "not bestowed one thought" on him. This indicates that the relationship between the two men was not a loving or friendly one. The two were not friends and did not care for one another on a personal basis. If they had been more friendly, one might expect Scrooge to have thought about Marley at least once after the latter's death.
When Scrooge sees Marley's ghost, he speaks to it "in a business-like manner, though with humility and deference." The fact that Scrooge addresses Marley's ghost with "humility and deference" suggests that Scrooge respected Marley when Marley was alive. Of course, he may also be speaking respectfully to the ghost at this moment because he is scared.
Scrooge also says to Marley's ghost, "you were always a good man of business," and "you were always a good friend to me." The first statement confirms that when Marley was alive, the relationship between him and Scrooge was a formal business relationship. However, the second quotation suggests that there was also some degree of warmth and friendship in the relationship. The fact that Marley's ghost comes to warn Scrooge so that Scrooge doesn't come to the same fate as him also suggests some friendly feelings in the relationship.