Alpha one gen 2

[Eastboundndown]

Hello, hope everyone is well. I am replacing The 5.7 In my boat with A 7.4 and was hoping someone might know if the outdrive has to be changed for larger motor..? Thx

 

[Bondo]

Ayuh,..... That depends on what drive, 'n what gear ratio is there now,.....

If it's an Alpha drive, it won't take the torque of the big block,......

 

[jesse_boston]

The 5.7 and the 7.4 have different gear ratios in the outdrive. You might be able to correct for it by using a different prop than would have been 'standard' for a 7.4 in your boat.
Not sure if the rest of it can handle the 330hp at the input shaft, for some reason the number '300' is bouncing around in my head as a limit for one of the outdrives, but can't remember if it is alpha.
EDIT: Bondo beat me to it, yeah you'll probably blow up the alpha.

 

[tpenfield]

Yes, very few Alpha drives mated to the big block engine (454). If you are gentle the Alpha might last . . . if not, there may be a Bravo outdrive in your future. ($7K ish)

As Jesse stated, you can probably adjust the prop choice to make up for the drive ratio difference.

 

[harringtondav]

I believe current Alpha drives are rated up to 300 hp. Early Alpha 2s were 250 hp. The new ones have larger, external snap ring Unis and a beefier lower pinion drive shaft. Higher torque capacity required this.

Per Bondo a big block has more torque than the Alpha can handle. Also, per TPenfield, you could control the big block torque with your throttle hand, but that defeats the whole idea of a 7.4. Merc mates a Bravo to their big blocks for a reason.

 

[Eastboundndown]

Just because I don’t like the answer doesn’t mean I don’t appreciate the responses.. Lol. thx everyone. I will upsize prop and I’m sure the alpha should hold up for The Motor “breaking in” period and that will give me time to try and find a good used bravo that I can afford. If I may I’d like to ask you gentlemen another... “probably stupid” question But here goes anyway.. When changing from alpha to bravo does this mean transom plate and gimbal house have to go also?

 

[Bt Doctur]

Correct, no Alpha parts will work with a Bravo and the engine will need a belt driven or crank driven raw water pump

 

[Bondo]

When changing from alpha to bravo does this mean transom plate and gimbal house have to go also?

Ayuh,..... From the motor's rear mounts, aft,...... everything is different,.....