Mercruiser Alpha Generation 1 Vs. Mercruiser Alpha Generation 2 Sterndrive Comparison

PPT has been providing the Marine Industry with both New & Remanufactured Mercruiser Sterndrives….(Read More) since 2002. During this time PPT established the Online Mercruiser Sterndrive Parts Catalogs which were developed to assist Online Shoppers easily locate the correct Mercruiser Alpha One Outdrive parts for their Mercruiser Alpha Model Sterndrives. Since day one PPT has always been committed to providing our customers with the level of Technical Support they receive when shopping locally. But PPT is not only one of the leading Online Suppliers of complete Mercruiser Alpha Model Sterndrives, but also both Original Manufacturer (OEM) and Direct Replacement Marine Parts from leading manufacturers such as Sierra, Barr, and GLM.

Some of the more common items found in the Online Mercruiser Alpha One Parts Diagram….(Read More)

• Mercruiser Alpha One Lower Unit….Read More
• Mercruiser Alpha One Water Pump….Read More
• Mercruiser Alpha One Bellows Kit….Read More

 

Figure 1 (Gen 2 Left / Gen 1 Right / MC1 Far Right)

 

Histroy of the Mercruiser Alpha Sterndrive

Beginning in 1983 Mercruiser introduced the R/MR/Alpha 1 series of sterndrive models. These units differed greatly from previous years not only in design but also in that the flywheel housing on the engine changed at this point. This creates one of the big break points customers should be familiar with when inquiring about re-powering older boats. Since the flywheel housing changed from 1982 to 1983, you cannot couple a new engine to a pre-1983 sterndrive unit as the rear engine mount spacing differs on the new engine and therefore will not match to the old style inner transom plate. The other difficulty is that the newer 14 inch flywheel utilize a larger coupler that prevents re-using the old flywheel housing on the new engine.

R/MR/Alpha Generation 1 model began in 1983 and ran production through 1990. The Serial Number Range for these models ranged from 6225577 Thru 0D469858

Alpha Generation 2 model was introduced in 1991 and are currently still in production. The Alpha Generation 2 models have been broken into several different Serial Number Ranges as follows:

1991 thru 1995 – 0D469859 Thru 0F679999

1996 thru 1997 – 0F680000 Thru 0K999999

1998 and Up – 0L100040 And Up

Gear Ratios

A very common question raised when replacing the Mercruiser Alpha sterndrives involves the gear ratio. NOTE: Mercruiser made the following gear ratio changes to the Alpha Model Sterndrives several years ago in effort to develop s stronger gear combination that would offer customers better overall Sterndrive durability. Be aware that these New Gear Ratios are a direct replacement for the older gear ratios. There is no noticeable difference in performance.

What was a 1.50:1 thru 1995, in 1996 changed over to a 1.47:1

What was a 1.65:1 thru 1995, in 1996 changed over to a 1.62:1

What was a 1.84:1 thru 1995, in 1996 changed over to a 1.81:1

What was a 1.98:1 thru 1995, in 1996 changed over to a 1.94:1

In 1998 Mercruiser introduced the 2.0:1 gear ratio to the Alpha Generation 2 Sterndrives which has since replaced the 1.94:1

SHIFT LEVER

One noticeable difference between the Alpha Gen 1 & Gen 2 Sterndrives is the shift lever as shown in Figure 2. The old style brass shift lever will not engage in the Generation 2 Transom Assembly and therefore prevents installing an Alpha Generation 1 Sterndrive on the Alpha Gen 2 Transom Assembly….(Read More).

TRIM CYLINDER MOUNTING PADS

Another noticeable characteristic between the Generation 1 & 2 sterndrives is the width of the mounting pads for the trim cylinders as shown in Figure 3. The Gen 2 drive has a substantially wider mounting dimension than the Gen 1.

INTER-CHANGEABILITY BETWEEN GENERATION 1 & GENERATION 2

Although the overall drive appearance is similar between the Gen 1 & Gen 2 drives there are several other characteristic differences between the 2 sterndrives. Figure 4 illustrates the overall size difference between the upper driveshaft housing. Although the mounting flange between the two drives will match the above mentioned difference prevent the two drives from being interchanged. Other changes between the two include;

The Alpha Gen II upper and lower housings are fastened together with two through bolts on either side of the drive along with the front and rear bolts, while the Gen 1 drives use one stud visible on either side.

Alpha Ones have two studs under the ventilation plate just above the prop.

Alpha Gen II drives do NOT have two studs with nuts above the prop.

Figure 2 (Gen 2 Left / Gen 1 Right)

Figure 3 (Gen 2 Left / Gen 1 Right)

Figure 4 (Gen 2 Left / Gen 1 Right)

 

**Select this link to learn the Product History of the 1, MC1, MR1, Alpha Generation 1 and Alpha Generation 2 Sterndrives……(Read More)