As far as I know diesel engine manufacturers do not follow NMEA standards. Most manufacturers have moved from a proprietary network interface to following the J1939 standard which is similar but not compatible to NMEA2000. If you are trying to get your engine data onto your NMEA 2000 electronics displays (NMEA 0183 does not support engine data) you first need to determine if your engine ECU's support J1939. The first clue will be in your connector wiring diagram as it will show the three CAN bus/J1939 connections (CAN/J1939+; CAN/J1939-; Shield). If you don't have the wiring diagram then reach out to Volvo or go onto boatdiesel.com with your serial numbers and someone there will tell you. You also need to make sure your ECU's actually support the interface (sometimes requires a SW update). In 1995 I am not sure how many manufacturers supported J1939 but it is easy to find out.
Next you would need a gateway device (one for each engine bus) that will bridge each engine network to the N2K network. This will allow the J1939 packets/PGN's to jump onto the N2K network where presumably your MFD's will grab and display the data. I purchased a couple from Maratron for under $200 each. You will also need to configure the gateways (only if you have more than one gateway) which requires an interface to a laptop. Your end configuration will have three separate, properly terminated CANbus networks; one for each engine supporting J1939 and one for your electronics that supports N2K.
Having gone though all of this last year I will tell you it sounds worse than it is. The support group at Maretron are really good and can walk you through any questions/issues that you might have.
Sorry but someone else will need to answer your hull questions. Either that or reach out to Tiara and I am sure they will give you your answers.