Alpha gear & prop question

P

Pessemist

Seaman
Joined
Sep 14, 2002
Messages
61
I blew the sterndrive on my 1988" Sun Dancer 268DA with the stock 7.4L engine

It originally had an Alpha 1 with 1.32 gear ratio.

I can get an STI aftermarket fairly cheaply but the closest gear ratio they offer is 1.47

Checking out this prop website calculator I see I can get very similar performance by moving from the stock prop of 15.25x15 to 15.25x16 (up 1 pitch).

I know calculated ain't real world but I was wondering f this would work? Finding an inexpensive 1.32 replacement drive is problematic.

I know these engines EAT Alpha 1 drives but an Alpha 1 is my only option.

STI will not warranty their drive with the big block.

I use synthetic gear lube and rarely run at WOT to baby my drive.

Any thoughts?
 
Tail_Gunner

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: Alpha gear & prop question

Pessemist said:
I blew the sterndrive on my 1988" Sun Dancer 268DA with the stock 7.4L engine

It originally had an Alpha 1 with 1.32 gear ratio.

I can get an STI aftermarket fairly cheaply but the closest gear ratio they offer is 1.47

Checking out this prop website calculator I see I can get very similar performance by moving from the stock prop of 15.25x15 to 15.25x16 (up 1 pitch).

I know calculated ain't real world but I was wondering f this would work? Finding an inexpensive 1.32 replacement drive is problematic.

I know these engines EAT Alpha 1 drives but an Alpha 1 is my only option.

STI will not warranty their drive with the big block.

I use synthetic gear lube and rarely run at WOT to baby my drive.

Any thoughts?
Click to expand...

If the sei is the choice you have without a rebuild dont stress it..gearing is miminal in your case. yes you may have to reprop but wait till the drive is on... there is now way to guess here..You may not even need to
 
Bondo

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,512
Re: Alpha gear & prop question

Pessemist said:
I blew the sterndrive on my 1988" Sun Dancer 268DA with the stock 7.4L engine

It originally had an Alpha 1 with 1.32 gear ratio.

I can get an STI aftermarket fairly cheaply but the closest gear ratio they offer is 1.47

Checking out this prop website calculator I see I can get very similar performance by moving from the stock prop of 15.25x15 to 15.25x16 (up 1 pitch).

I know calculated ain't real world but I was wondering f this would work? Finding an inexpensive 1.32 replacement drive is problematic.

I know these engines EAT Alpha 1 drives but an Alpha 1 is my only option.

STI will not warranty their drive with the big block.

I use synthetic gear lube and rarely run at WOT to baby my drive.

Any thoughts?
Click to expand...

Ayuh,.... It's SEI, 'n iboats sells 'em,.... Seein's yer startin' with a 15" prop,...

You've got available pitch range in yer favor.... ya might see a Nice improvement....

Like Tail Gunner said,.. Try what you've got, 'n go from those numbers ya get at sea-trials..
 
M

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Re: Alpha gear & prop question

Pessemist,

I think the 1.32 ratio in that big of a boat behind that much torque is what did the drive in. A 1.47 is much more in line with what that boat and engine combo needs anyway. I bet your boat will be more enjoyable than ever with the SEI 1.47.
 
jestor68

jestor68

Commander
Joined
Jun 12, 2012
Messages
2,308
Re: Alpha gear & prop question

Since SEI offers several gear ratios in their 116 drive, it seems that you would better off with a lower ratio; such as 1.62 or 1.81.
 
P

Pessemist

Seaman
Joined
Sep 14, 2002
Messages
61
Re: Alpha gear & prop question

I think the 1.32 ratio in that big of a boat behind that much torque is what did the drive in. A 1.47 is much more in line with what that boat and engine combo needs anyway. I bet your boat will be more enjoyable than ever with the SEI 1.47
Click to expand...

While I would hope so, the Searay 268DA Sundancer came stock with the 1:32 ratio from the factory when fitted to the large block 7.4L V8.

They reserved the 1:50 drives for the V6's and small block V8's

I wish someone who had that big a boat and was forced to swap the 1:32 for the 1:47 could give me their real world experience.
 
Tail_Gunner

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: Alpha gear & prop question

Pessemist said:
While I would hope so, the Searay 268DA Sundancer came stock with the 1:32 ratio from the factory when fitted to the large block 7.4L V8.

They reserved the 1:50 drives for the V6's and small block V8's

I wish someone who had that big a boat and was forced to swap the 1:32 for the 1:47 could give me their real world experience.
Click to expand...

Ok dont get caught up in this. Bondo or Don ive read the the 1.9 gear's are more robust than a 1.5 is that true...get one of those two to respond. There are some trival points to this whole thing..but they are trival
 
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