What sort of pressure does your raft end up at once inflated? I'm asking because a buddy that had an inflatable boat some years back only had to inflate it to around 5 psi to make it hard as a rock. If your raft isn't any different then the matching compressor may be a high volume at low pressure sort of deal that won't fill up a tire past spongy soft.
And certainly the sort of compressor that you would use to fill bike or car tires would be a small volume higher pressure pump that would take about a week to fill a typical inflatable boat.