If your Mariner 30 HP model engine looks like this photo, is a disguissed Tohatsu outboard made in Japan and exported to USA for Mariner/Mercury brands with their own characteristic logos and colours. 25 & 30 HP has the same cc, that is 430, the 25 HP has an air restriction plate on the carb entrance and throttle adjustments to lessen power.
What manual are you looking for, owners manual, spare parts manual ? Have all the requested information available, I'm a Tohatsu dealer, just email me to send whatever info you need. Pleased to lend you a hand.