Swapping a 1.65 ratio for a 2.0?

[caphilli]

The upper portion of my outdrive is a SEI with a 1.65 ratio. It's on a 3.0l 4-cyl mercruiser. Alpha 1 Gen 2.
Boat is a 176 Sea Ray.
The upper has gone bad and I think its a bearing because the shaft that comes through the top has a ton of play.
A friend is selling a Mercruiser upper with a 2.0 ratio.
Would that swap out pretty easily?
The prop I'm currently running is 0A1916X 19P and runs well.
Thanks.

 

[alldodge]

The 1.65 and 2.0 both use 24/24 gears in the upper housing so there would be no change. Do check the lube for metal

 

[racerone]

I thought the SEI units have a 3 year no question asked warranty ??

 

[Bondo]

The upper portion of my outdrive is a SEI with a 1.65 ratio. It's on a 3.0l 4-cyl mercruiser. Alpha 1 Gen 2.
Boat is a 176 Sea Ray.
The upper has gone bad and I think its a bearing because the shaft that comes through the top has a ton of play.
A friend is selling a Mercruiser upper with a 2.0 ratio.
Would that swap out pretty easily?
The prop I'm currently running is 0A1916X 19P and runs well.
Thanks.

Ayuh,....... Welcome Aboard,....... Yer motor is Supposed to have a 2.0:1 ratio drive,......

 

[caphilli]

I thought the SEI units have a 3 year no question asked warranty ??

I believe they do. And I was excited to send it off and get a fixed one. The guy who sold me the boat said the sei drive was only a year old - wrong. It was purchased in '08. I hate people who lie.

 

[caphilli]

The 1.65 and 2.0 both use 24/24 gears in the upper housing so there would be no change. Do check the lube for metal

Thanks. I never saw metal, so assume the damage was done a while ago. My lower is a 2:1 ratio. So would the 2.0 ratio upper be fine?

 

[caphilli]

The 1.65 and 2.0 both use 24/24 gears in the upper housing so there would be no change. Do check the lube for metal

Thanks.
My lower is a 2:1 ratio. So would the 2.0 ratio upper work fine with no change in the prop? Boat was running around 6000 rpm with the 1.65, so I assume that'll drop with the correct unit.

 

[alldodge]

Not understanding so what I'm saying is both the 2.0 and 1.65 uses the same gears in the upper section 24/24 gears. The ratio is changed in the lower. The 2.0 uses 14/28 gears and the 1.65 uses 13/21 gears.

If you are using your same lower, either upper (yours or other one mentioned) then you will still have the same final ratio you previously had

 

[Bondo]

Boat was running around 6000 rpm with the

Ayuh,....... That's atleast 1200 rpms to much,......

I'm surprised ya havin' blown it to bits,.....

 

[Scott06]

Ayuh,....... That's atleast 1200 rpms to much,......

I'm surprised ya havin' blown it to bits,.....

Tach must be way off, if he is actually running a 1.65 drive behind a 3.0 he’s gotta be running a 15” prop to even get to 4800 rpm

 

[caphilli]

Tach must be way off, if he is actually running a 1.65 drive behind a 3.0 he’s gotta be running a 15” prop to even get to 4800 rpm

That's where I'm confused. Because it idles right around 800-1000. Prop is 19pitch. But looking at the tach when I'm underway it's right around 6k

 

[alldodge]

That's where I'm confused. Because it idles right around 800-1000. Prop is 19pitch. But looking at the tach when I'm underway it's right around 6k

The tach is off at idle as well, should be idling at 700

 

[caphilli]

Not understanding so what I'm saying is both the 2.0 and 1.65 uses the same gears in the upper section 24/24 gears. The ratio is changed in the lower. The 2.0 uses 14/28 gears and the 1.65 uses 13/21 gears.

If you are using your same lower, either upper (yours or other one mentioned) then you will still have the same final ratio you previously had

Okay, so if my lower unit (Merc 2:1) I would be fine matching it with an upper unit that is 2.00 ratio without having to change the prop? Prop is currently a 19pitch.

 

[alldodge]

Okay, so if my lower unit (Merc 2:1) I would be fine matching it with an upper unit that is 2.00 ratio without having to change the prop? Prop is currently a 19pitch.

Correct, but follow what I'm saying

Its my understanding that you have a 2.0 drive with a bad upper. Your drive would there for consist of
upper 24/24 gears
lower 14/28 gears

The other upper drive which was 1.65 drive would consist of
upper 24/24 gears
lower 13/21 gears

Both drives used the same upper gears, it was the lower which changed the ratio. So swapping uppers does not change what you started with so far as the ratio

 

[caphilli]

Correct, but follow what I'm saying

Its my understanding that you have a 2.0 drive with a bad upper. Your drive would there for consist of
upper 24/24 gears
lower 14/28 gears

The other upper drive which was 1.65 drive would consist of
upper 24/24 gears
lower 13/21 gears

Both drives used the same upper gears, it was the lower which changed the ratio. So swapping uppers does not change what you started with so far as the ratio

I believe I'm following.
So yes, the 1.65 (SEI drive) that went bad was matched with a 2:1 lower.
The lower is still good, so I'm thinking of replacing it with a 2.0 Merc Upper.
That setup should work just fine - just like the SEI setup did?
Also, is there any truth to the 1.65 drive failing because that upper wasn't supposed to go with a 3L 4-cyl engine? That's what I've heard and read. Also heard that is why the engine was up at 6k rmp. Any truth to either?

 

[alldodge]

That setup should work just fine - just like the SEI setup did?

Correct

Also, is there any truth to the 1.65 drive failing because that upper wasn't supposed to go with a 3L 4-cyl engine?

No, this would not cause the any failures. Lack a maintenance would be my first guess as to why it failed

Also heard that is why the engine was up at 6k rmp. Any truth to either?

No, not the issue. You tach is bad and it never reached 6000 rpms, if it did you would be buying a new motor and pickup pieces of the motor

 

[caphilli]

Correct


No, this would not cause the any failures. Lack a maintenance would be my first guess as to why it failed


No, not the issue. You tach is bad and it never reached 6000 rpms, if it did you would be buying a new motor and pickup pieces of the motor

Thank you for all of this! It's very helpful.

 

[Bondo]

Also, is there any truth to the 1.65 drive failing because that upper wasn't supposed to go with a 3L 4-cyl engine? That's what I've heard and read. Also heard that is why the engine was up at 6k rmp. Any truth to either?

Ayuh,...... Both statements are Untrue,......

The 3.0l don't make enough power to destroy an upper unit,.....
More likely, it was run, low on oil,.....

The 3.0l needs the lowest gear ratio, the highest numbers, to make it run at idle to 'bout 4800 rpms, while pushin' yer boat,......

With the 1.65:1 ratio, which is usually for the 4.3l motor, or the 5.0l motor in huge heavy hulls, yer 3.0l shoulda been turnin' Maybe 2,000 rpms,......
Which leads to the speculation, yer tach is junk, or switched to a wrong setting,......

Check yer tach, against a known good shop tach,.....

 

[achris]

Are you referring to a genuine 2.0:1, or just rounding the 1.94:1 to 2?

I've condensed the above table to make it a little clearer...



Now we can see that the overall ratios of 2 and 2.4 are achieved by using the same upper as the 1.62 and 1.94, but a different lower gear set. When changing just an upper or just a lower, but mindful of exactly what the tooth count in the 'other' housing is.

Chris.......

 

[Bondo]

Are you referring to a genuine 2.0:1, or just rounding the 1.94:1 to 2?

Me,..??..?? just roundin',.......