Drive Shaft Lower Unit for Mercruiser #1 with Preload Pin 1974-1982 45-51939A1 - GLM11110 Vertical Drive Shaft for a Mercruiser # 1 drive. This drive shaft is easily distinguishable because of a preload pin at the top of the shaft. The pin is about .250 in diameter and about .650 long. It will not fit MR Alpha drives. This item replaces Mercury Marine Quicksilver #s 45-41939A1, 45-41939F1. About Us Basic Power and its staff want you to feel 100% confident in your purchases. Here are a few reasons why: Multi-Million dollar inventory In Stock and Ready to Ship from our huge inventory Shipped Same Day when order is placed before 2pm Highly Technical staff available Tracking numbers are visible through purchase history right from your computer We sell ONLY quality marine specific parts Contact us through messaging system PayPal payments and Credit Cards through Payment System are accepted Ships best way via USPS or UPS Shipping Shipping rates of $12 and less are eligible for combined shipping. Items with $13 or more shipping cannot have the shipping costs combined. Our normal handling time is 1-2 days. Payment We accept payment by any of the following methods: Payment System(Visa,MasterCard,PayPal,Stripe and many others)! Please pay as soon as possible after winning an sale, as that will allow us to post your item to you sooner! Returns No Returns Accepted on this item.