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Alpha 1 Gen 1

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Mark2376

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I have an Alpha one Gen one outdrive with a 1.98 gear ratio that came off a 1988 3.0 liter. I’m looking at an alpha one Gen one with a 1.84 gear ratio that came off a1990 4.3 liter. Will it work on mine?
 
Mark2376 said:
I have an Alpha one Gen one outdrive with a 1.98 gear ratio that came off a 1988 3.0 liter. I’m looking at an alpha one Gen one with a 1.84 gear ratio that came off a1990 4.3 liter. Will it work on mine?
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Ayuh,..... Not very well, as you'll need a much smaller prop to make up the difference,...
 
Mark2376 said:
What prop adjustments would look at doing? I’m currently using this one
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go down in pitch about 2" from what you were running with the 1.98. The 1.84 has less gear reduction so you need a lower pitch prop to try and compensate. Issue will be if yo were already running a 15" or 17" prop you may run out of available pitches . If you were running a 19" drop to a 17".

This worked for me going the other direction- I am running a 1.81 in an application that should have a 1.62 ( swapped a 4.3 for a 5.0) ... went up from 19" to 21" to compensate for the greater gear reduction.
 
Need more info.

Length and brand of boat.

What are your max RPM when at wide open throttle and trimmed up for max performance with you alone in the boat?
 
Mark2376 said:
I’m running a 3 blade aluminum, with a 15” diameter and a 17” pitch.
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As Kghost points out, if your WOT RPM is in spec 4400-4800 or so (your version of the 3.0 could be 4200-4600) then you can probably drop to a 15" pitch and have similar performance.

Would be good to know what you had in terms of RPM. Not that you have to keep it at WOT just if it can get to the upper range of recommended WOT rpm it is propped correctly and won't be lugging the engine through the rpm range
 
One other question,
1989/1990 is when merc went from Gen 1 to Gen 2 for Alpha.

Gen 2 use a different input shaft and have 4 nuts and bolts, 2 per side, visable.
Also the trim ram shafts use Plastic bushings vs rubber bushings with different shafts for each design.
Other changes also but what is described is enough to tell the difference.

So if a gen 2 its not for you.
 
1991 is the first year for Gen 2 going into production. I had a 1991 Sea Ray that had (by serial number) one of the last gen 1 drives made, assuming the engine was made in 1990.

Serial OD 469859 and up is Gen 2 if the OP can read the serial number
 
Found this for everyone's future reference:

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
 
How old is old?

Why are you wanting to change the drive?

Regardless of the age, If it will not go beyond 2500 rpms without issue, changing the prop or the drive will not solve what ever is your problem.
 
kghost said:
How old is old?

Why are you wanting to change the drive?

Regardless of the age, If it will not go beyond 2500 rpms without issue, changing the prop or the drive will not solve what ever is your problem.
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kghost said:
How old is old?

Why are you wanting to change the drive?

Regardless of the age, If it will not go beyond 2500 rpms without issue, changing the prop or the drive will not solve what ever is your problem.
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The old drive is toast and all I do is putt around lake and troll. I was satisfied with the boat and buying a new outdrive is outrageous. I don’t know why I’m even explaining this ****. All im looking for is some boat knowledge that I do not acquire. Like changing outdrives gears pitch and size of prop. Gees.
 
If you had said all of this in your first post then you would have received the answer you were looking for.

99.9% who post questions even like your original post are having problems or need to understand like what you asked.

"" will a different ratio drive work wirh my boat"

Without knowing why it is ASS UMED you had a problem of some kind.


In the end, now that you issues/concern is revealed,

You can use any gen 1 drive if you have Zero plans to go above 2500 rpm.

Facebook Market place is loaded with gen 1 outdrives of all ratios.

I found one for a 4 cyl like yours for a friend for $450 complete and in good shape
 
Mark2376 said:
The old drive is toast and all I do is putt around lake and troll. I was satisfied with the boat and buying a new outdrive is outrageous. I don’t know why I’m even explaining this ****. All im looking for is some boat knowledge that I do not acquire. Like changing outdrives gears pitch and size of prop. Gees.
Click to expand...

kghost said:
If you had said all of this in your first post then you would have received the answer you were looking for.

99.9% who post questions even like your original post are having problems or need to understand like what you asked.

"" will a different ratio drive work wirh my boat"

Without knowing why it is ASS UMED you had a problem of some kind.


In the end, now that you issues/concern is revealed,

You can use any gen 1 drive if you have Zero plans to go above 2500 rpm.

Facebook Market place is loaded with gen 1 outdrives of all ratios.

I found one for a 4 cyl like yours for a friend for $450 complete and in good shape
Click to expand...
Thank you
 
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