Midshaft Talk - Building, Rebuilding, SN vs. RN, etc.

[Flave]

Only comes out between the 2 rear seals when you use the grease fitting.

When the shaft is out, you can grease everywhere by hand.

Precisely this is what I'm doing, when I use the grease fitting nothing comes out. It comes out there

It can be obstructed ? Or the 2 rear seals are mounted too tight.

 

[JetManiac]

How far is the rearmost seal pressed in? If it is pressed in too far, then yes it will be blocking the grease hole inside.

 

[Flave]

How far is the rearmost seal pressed in? If it is pressed in too far, then yes it will be blocking the grease hole inside.

The rearmost seal is pressed 2mm.
I have an old midshaft housing and a rod get in in my new midshaft housing impossible to push in

 

[MTRHEAD]

Midshaft press-through is critical because this helps to determine the amount of spline overlap. The factory specified amount is 19.5-20.5mm as measured between the rear of the housing (not the rear of the seal) and the rear of the shaft.

View attachment 168745

When completing a build it is important to check spline overlap, especially with a/m hulls, custom builds, and setback pumps with a/m shafts.

Degrease both driveshaft and midshaft splines first. Install and align pump. Then put a small amount of grease only at beginning of the driveshaft splines and then install midshaft. Carefully remove midshaft and check how far the grease was pushed. Sometimes you need to repeat several times but this is the only way I know to accurately check spline overlap.

If you need to press shaft farther in to correct for a spline underlap, you can add an additional washer behind midshaft coupler to maintain alignment.

View attachment 168746

Got a few questions on a recent midshaft issue

The shaft removed from a 1990 superjet (100% original) doesn’t match shaft pushed out of 1998 Superjet. Nor is the 19.5mm achievable as shown by jet maniac. The shaft bottoms out long before 19.5mm sticks out. 1/4”++

#1. Did the 98 I got the shaft from have an aftermarket shaft that’s not to spec?
#2. Are they really different?
#3. Can someone measure a true known OEM 94-20 shaft

I find that the splines are about 6-7mm, at least, farther up or forward in the 94-20 shaft than the 00-03. Not technically enough drive shaft engagement

so I’m really hoping my 98 shaft must of been a typical junk aftermarket than oem.

however coupler mounting edge to end is identical on both so I’m guessing it’s intended for a superjet 94-20 regardless of oem or Aftermarket. It just isnt really the same size between models (wouldn’t surprise me) or a piss poor job of copying

see pic

 

[JetManiac]

Got a few questions on a recent midshaft issue

The shaft removed from a 1990 superjet (100% original) doesn’t match shaft pushed out of 1998 Superjet. Nor is the 19.5mm achievable as shown by jet maniac. The shaft bottoms out long before 19.5mm sticks out. 1/4”++

#1. Did the 98 I got the shaft from have an aftermarket shaft that’s not to spec?
#2. Are they really different?
#3. Can someone measure a true known OEM 94-20 shaft

I find that the splines are about 6-7mm, at least, farther up or forward in the 94-20 shaft than the 00-03. Not technically enough drive shaft engagement

so I’m really hoping my 98 shaft must of been a typical junk aftermarket than oem.

however coupler mounting edge to end is identical on both so I’m guessing it’s intended for a superjet 94-20 regardless of oem or Aftermarket. It just isnt really the same size between models (wouldn’t surprise me) or a piss poor job of copying

see pic

The shaft on the right in your pic is definately not a 98 SJ RN shaft. The RN midshaft shaft has a shelf on it where the coupler washer rests that is larger in diameter than the shaft itself.

 

[MTRHEAD]

The shaft on the right in your pic is definately not a 98 SJ RN shaft. The RN midshaft shaft has a shelf on it where the coupler washer rests that is larger in diameter than the shaft itself.

Thank you - that means it’s probably a Chinese copy

 

[JetManiac]

Thank you - that means it’s probably a Chinese copy

It looks like an oem shaft from another ski.

 

[JetManiac]

Got a few questions on a recent midshaft issue

The shaft removed from a 1990 superjet (100% original) doesn’t match shaft pushed out of 1998 Superjet. Nor is the 19.5mm achievable as shown by jet maniac. The shaft bottoms out long before 19.5mm sticks out. 1/4”++

#1. Did the 98 I got the shaft from have an aftermarket shaft that’s not to spec?
#2. Are they really different?
#3. Can someone measure a true known OEM 94-20 shaft

I find that the splines are about 6-7mm, at least, farther up or forward in the 94-20 shaft than the 00-03. Not technically enough drive shaft engagement

so I’m really hoping my 98 shaft must of been a typical junk aftermarket than oem.

however coupler mounting edge to end is identical on both so I’m guessing it’s intended for a superjet 94-20 regardless of oem or Aftermarket. It just isnt really the same size between models (wouldn’t surprise me) or a piss poor job of copying

see pic

This is a new OEM SJ midshaft for comparison. Your 98 shaft should look like this.



See the lip I was talking about

 

[NSRSSR]

The rebuild kits have a couple O-rings in them - where do the O-rings go? Can you run without them?

 

[JetManiac]

The rebuild kits have a couple O-rings in them - where do the O-rings go? Can you run without them?

Inside the rear of the midshaft shaft itself. There are 2 grooves where they go. They seal water from getting to the splines and washing out the grease.

 

[Mike75]

Didn’t see any mention about how far the front seal needs to be pressed into the midshaft housing. Is it critical? I have mine almost touching the steel keeper

 

[JetManiac]

Didn’t see any mention about how far the front seal needs to be pressed into the midshaft housing. Is it critical? I have mine almost touching the steel keeper

Front seal is pressed in as far as it can until it hits the circlip.