It looks like in 1988, the Sea Nymph Fishing Machine was made in a 14’ model or 16’ model. If you can forward us the model number (161 for example) we can check with our manufacturers to see if there is a custom cover available.
If you no longer have that information, you might try the link below. These are semi-custom fit covers that seem to closely fit the description of your boat you have provided. To be on the safe side, you might want to measure it using the guidelines on the page.
V-Hull Fishing Boat Cover, OB with Motor Hood
Please let us know if we can be of further assistance.