1987 V20 with a 1990 Yamaha 150

Thanks for all the replies. It seems that you guys are really informed about this boat. I have talked to Steve over in Fla. at Wellcraft and he is going to send me a copy of the plans for this boat. Where is the second HIN number? Is it under the rub rail? Also, on the Yamaha...I have heard that the shafts are subject to the onslought of the brine. Maybe a good idea to keep on in the shop. Oh, by the way anyone have an idea on the gear ratio of the 1990 Yamaha 150, not sure on the "engine family name". I I have spoken to some of my outboard guys and they tell me that NGK standards are the plug to burn in this outboard. It also looks like just judging from the bulkhead that this boat was laid with a pre-fab stringer/grid system. I guess I won't know till I get the plans, do you guys have an idea? Since I can't and won't pull the liner. Thanks guys for the welcome!