Lower Unit Replacement

[zul]

Working with NuWave on a lower unit replacement: Current outdrive: Aplha 1 Gen 2 with a 1.84R gear ratio. The sales guy says that he'll send out a 1.81.

Is there a difference between 1.84 and 1.81? Other than .03?!! The sales guy says that they are the same and compatible. And that 'you never know what gears you've got in there'. Really?! My boat is a 1994 with 125 hours ... I'm pretty certain that everything is origional. The lower unit states 1.84R.

I only need the lower unit ($850 plus ship). But I would like to avoid the wrong lower unit and 20% restocking fees plus return ship ...

So, lower unit: 1.81 vs 1.84R. Everything is standard, common and the gear ratio isn't critical?!?

You can always believe the sales guy ... right?

Thx,

zul

 

[thumpar]

If you are talking about the lower and not the whole drive the tooth counts are the same so you would end up with the same ratio in the end. At that price I would assume it is just the lower unit.

 

[NHGuy]

Exactly, the sales guy is not aware, but the ratio occurs in the top half of the drive. He is still sending the correct lower if it's as you said.

 

[achris]

Bottom line? Use the new lower and you'll not know the difference.

Back story. For the most part the overall ratio is determined by the gear tooth count in the top box. The lower box being a 'constant'. Until roughly 1996 (don't quote me on the year, could be one or two either side) the lower gears were 17:28 and the different top box gears accounted for the overall ratio (17:19 gave 1.84:1, 22:20 gave 1.50:1, 20:24 gave 1.98:1 and 24:24 gave 1.65:1).... Merc then changed the tooth count of the lower gears to 13:21, for better strength and noise reduction. This altered the lower box ratio from 1.65 to 1.62 and thus the overall ratio with the other gear sets. (17:19 now gives 1.81:1, 22:20 gives 1.47:1, 20:24 gives 1.94:1 and 24:24 gives 1.62:1)....

There are other ratios and you can find all that information up in the sticky section.

HTH,

Chris.......

 

[Fun Times]

[h=3]Gear Ratios[/h] 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

Alpha Drives
NUMBER OF TEETH PER GEAR
(gear case gears at 14-28)
RATIO, DRIVE, DRIVEN,
2.40:1, 20, 24
(gear case gears at 17-28)
1.98:1, 20, 24
1.84:1, 17, 19
1.65:1, 24, 24
1.50:1, 20, 22
1.32:1, 16, 20
(gear case gears at 13-21)
1.94:1, 20, 24
1.81:1, 17, 19
1.62:1, 24, 24
1.47:1, 20, 22
MERCRUISER GEAR RATIOS - Blue Water Marine
**************************************************************************************

It is sort of important to know which lower unit gear case you are getting as the lower has two sets of gear sets/number of teeth options as seen below but since he's sure the lower unit they are sending you fits the 1.81: / 1.84:1, the gear teeth numbers are the same.

-	1623-815822A53	GEAR HOUSING ASSEMBLY, Standard Rotation (1.47:1, 1.62:1, 1.81:1 AND 1.94:1 RATIO)	815822A43	SS/ACT		$2,064.29	$1,848.88	1
-	1623-815822A55	GEAR HOUSING ASSEMBLY, Standard Rotation (2.00:1 AND 2.40:1 RATIO)	815822A45	SS/ACT		$2,064.29	$1,848.88	1

 

[zul]

With all the good response, I made the lower unit purchase. Took the damaged lower unit off the boat yesterday and came across two surprises:

1. Near the L shaped gear shift attached to the front of the old lower unit, there is a small plastic hose with 'turn and snap in' connector. Half of this connector is located inside of the upper unit and looks almost impossible to re-connect once the lower new unit. It's a small black hose with white connector. How can this connector be reconnected? I didn't see/hear mention of this in any of the videos I've watched ... Looking for ideas re: how to reconnect and what is it? It does look like some space on top of the plate on upper, but it looks like a difficult and tight space at best.

2. When I pulled off the old lower, a small diameter 2 inch rod fell out. The rod has no threads, it's got a groove worn into it. The groove is worn about half way through the rod. The bottom end looks worn away completely until it may have just seared off. Perhaps by dremal tool, perhaps by spinning boat parts?! Any idea what it could be? I am optimistically hopeful that it fell into the unit at factory install or when someone was installing a water pump, as in, non essential, not necessary part and not going to ruin my day (gulp!). Trying to get a pic of it on here, will keep trying.


Thanks for your input and ideas ...

 

[zul]

[No message]

 

[thumpar]

The hose is from the pitot tube. That is what runs the speedometer. You lift the tab and turn it to pop it off and the opposite to put it back on

My guess on the rod is that it is the rod from the shutters.

 

[achris]

The hose is from the pitot tube. That is what runs the speedometer. You lift the tab and turn it to pop it off and the opposite to put it back on

My guess on the rod is that it is the rod from the shutters.

Right on both counts.

OP, have a look in the stickies and my videos of removing the drive and reinstall the drive. I refer to the speedo tube a couple of times.

Chris......

 

[zul]

Thanks gang. I guess that means I'll need to tear into my exhaust to see if there are flappers or not?!? Lower unit just arrived and goes in this afternoon. Fingers crossed this all goes smooth .....................

 

[Rick Stephens]

You want to install the upper gear case onto the lower with the upper off the boat. Don't try and do that with the upper still installed. You will screw up seals and have trouble with shift shafts.

Once you have the outdrive reinstalled, you raise the tilt all the way and then can access the speedometer hose and stick it on the twist lock fitting pretty easily.

Rick

 

[zul]

Ok, so we got er up in der. Dang. Two more issues:

1. The lead bolt at the front of the lower was sent with the new lower. At first, it threads by hand. Soon after, the going gets tough. And with half way to go, this new factory bolt does not want to sit where it's supposed to. Hmmm. If it were a 1/4 inch shorter, we might convince it to go. But with a 1/2 inch to go, I'm not into forcing it. What to do?!!

2. Speedo hose: old snap and twist not compatible with the new fancy prong. Ergh. Not sure to find a new part, cut the old or if there's a way to mate these two?!!

Any ideas welcome. Guess I'll call Nu Wave on Monday to see about that bolt length being too long.

 

[Fun Times]

For the speedometer you'll need to order Merc part number 860382. Note from SEI: Uses the latest style speedometer fitting - OE#860382. This part is not included and will be required to have a working speedometer.http://www.sterndrive.cc/product/Fit...-815822A5.html


As for the bolt, you may need to clean the paint inside the hole as the bolt/screw appears to be shorter than the stud your old unit should have had.... I found an old topic where we went over this, wondering if still active forum member tahoejag is able to provide any additional info of how he made out installing his. In the mean time, I wouldn't force it down without confirming something.... http://forums.iboats.com/forum/engin...unit-bolt-stud

Item number 4, http://www.mercruiserparts.com/bam/s...30862/2686/140

4	16-57984	----STUD, (.437-14/.437-20 x 2.380)		ACT		$16.40	$16.00	1
4	10-806327	----SCREW, (.437-14 x 1.750)		ACT		$4.90	$4.78	1

 

[Rick Stephens]

Take the fitting for the speedo tube off your old outdrive and screw it on the new drive.

Use two nuts locked together to screw the stud in.

 

[zul]

Cleaning the paint/debris out of the threads ... Is there a chemical or special process that you can suggest? Mini wire brush? Will it require taking off the lower unit?? We had a b^%$#h of a time lifting and sliding in 'that last inch or two' without forcing ....

Seems like the threads in the lower unit are plenty deep, but they are not accepting the new bolt very well. Again, it hand threads nicely but only to a point where things get super tight.

I am an armchair mechanic but always concerned to not cross or force things. Thx again !!

 

[Rick Stephens]

The way I would do it is run a bottoming 7/16 x 14 tap into the hole. That would make sure it was perfect. Use a pair of fine thread - 7/16 x 20 - nuts jammed together to run the stud in. I use Vibra-tite on all stainless into aluminum bolts. Prevents galling, helps hold them in place and keeps them from corroding.

 

[Rick Stephens]

BTW< I don't know what you meant by "does it require removing the lower unit" I wouldn't do the assembly without it all being off the boat and sitting in some sort of drive stand - even a couple 2 x 4s the right width apart. Makes it very easy to properly get the upper lined up and dropped onto the lower unit without damaging seals. No way I would try and clean those threads out with the unit together either.

 

[zul]

After speaking with SEI tech support, the idea was that the bolt, not cross threaded, but was more likely being forced in at an angle. They also suggested that the factory spray on loc-tight could also be making things difficult.

So we took the lower off. Cleaned up all the threads and again installed the lower. The lead bolt was much happier on it's way in this time and we completed the install.

Next, gear oil for the outdrive.

I haven't found any steps or suggestions on the first time starting procedure. The obvious, add the muffs, turn the water on. Place the shifter into neutral.
IS THERE ANYTHING ELSE?! Normal start and keep at idle until everything warms up, shut it down and head to the lake ... I guess?! I would hate to miss a step here.

There are break in instructions: 5 hours at slow idle ... Wow! Like half a day puttering on the lake for break in.

Yes, I am nervous to put the boat into gear with the brand new lower ..... So far a success. Looking forward to happy boating again next week!!

zul

 

[Rick Stephens]

Is it really 5 hours at idle? Wow, I don't remember that, I thought it was like 5 hours at something like under 2k RPM.

Fill her up and stick her in gear. Does it lock up in forward, in reverse and go back into neutral? Fire it up and do your driveway tests.

Rick

 

[zul]

Ya, 5 hours under 2k. Must have typed it wrong, but that's a boat load if time!!

I've got to drive 2 hours to get marine motor oil and outdrive oil. Between that and work, it's gonna be a few days until I can move ahead with these final steps and test.

Thanks for your help Rick! I'll have to post up the final result next week.

Until then!!

zul