How to Remove 1994 SN SJ Drive Shaft?

1994 Yamaha Square Nose Super Jet

HIN No.: YAMA1937B494
PRI I.D.: GH7 0800726



Other than a new drive shaft, midshaft bearing any other parts I will need?

I noticed that the pump was shimmed. Is there an alignment tool I should use?

A new midshaft , you replace the midshaft and the driveshaft as a set when that happens , it the driveshaft has that kind of wear - damage so does the midshaft , the difference is you can't see the damage inside the midshaft ,

You need the midshaft alignment tool , align the driveshaft to the hull by shimming it using the midshaft tool , then put the midshaft in and last align the two couplers with the dampener removed using shims , note the shim locations remove the engine or slide it far enough forward to get the damepner in then put the shims back in their respective locations and tighten everything down.

Understood. Suggestions where to buy?
Is there an alignment tool I need to assure proper alignment of the midshaft to engine or midshaft to pump?

Oh, and why do you think this happened?

thank you

Misalignment and more importantly years and years of use and abuse most likely .

No and no , it works just the way I stated , you align yhe shaft to the hull, everything keys off of the driveshaft alignment .

Weeks brothers on here has them .

E350 said:

Understood. Suggestions where to buy?
Is there an alignment tool I need to assure proper alignment of the midshaft to engine or midshaft to pump?

Oh, and why do you think this happened?

thank you

Click to expand...

Try Jetmaniac he stocks all that stuff .

94 square nose powa blew that thing to pieces like it was tissue paper!!!

It’s mostly lack of maintenance. Those splines need to be clean and greased. In 30 years I have never once met or even heard of a rider removing his mid shaft to clean/lube the splines, EVER! It’s also common for sand to collect in the hulls driveshaft tube, what do you think happens when the pump is pulled and reinstalled?

The driveshaft failed last August 2024.

In August 2018, I had the housing rebuilt with my intermediate shaft. I did not recenter the pump drive shaft. I just assumed that if it was centered before, then it would stay centered with the new intermediate shaft bearing housing. I did grease the shaft. I also pumped some marine grease into the grease tube at that time. However, the grease tube is completely dry now and devoid of grease.

In 2020 I replaced the 650 6MB in it with a 701 61X and I eyeballed the alignment of the engine coupler with a straight edge. I did not use a feeler gauge the way the guys use it on youtube. But looking at my photos, I am not confident that I aligned it "perfectly." It is close, but not perfect. I will definitely align the new drive shaft perfectly.



Are aftermarket drive shafts and intermediate shafts as good or better than oem? Or do you guys recommend oem drive shafts and intermediate shafts?

Can I place the intermediate shaft into the intermediate bearing housing myself or should I have Jet Maniac do that?

I will know a little more after I pull the engine and remove the intermediate bearing housing and shaft.

I am definitely a rookie here, making rookie mistakes.

I will also inspect and grease the FX-1 and the 2019 SJ bearing housings.

I think Jetmaniac can supply any driveshaft you need , they are cut down and resplined OEM shafts and are as good as you are going to get quality wise , Midshaft he can supply as well , send him a message .

You need a hydraulic press to replace the midshaft and it has to be pressed in to a certain distance or specification .

Question: The jet pump is out and When I spin the drive shaft, the Impeller (item 39) spins BUT the fan in this housing below DOES NOT SPIN.



Is it supposed to spin when the Impeller (item 39) spins?

I might be unqualified to answer this question since I'm not sure what fan you're referring to, but if you're talking about the stator vanes directly behind the impeller then no, those are solid and do not move. They're angled the opposite direction that the impeller spins to straighten out the thrust (or something like that).

E 350 sometimes you crack me up, I am not gonna lie

@WFO Speedracer then gladly I am doing my job!

My highest function on any forum is to ask the stupid questions , , ,

E350 said:

@WFO Speedracer then gladly I am doing my job!

My highest function on any forum is to ask the stupid questions , , ,

Click to expand...

This is so tempting but I will just post this instead

See that sand?
It's not sand.
A magnet proves that those are metal filings.
The splines inside the midshaft are gone. It is smooth.
But the midshaft bearing spins smoothly.
So can the housing be rebuilt with a new intermediate shaft?

Use new seals and bearing.

I hate to ask this but I seriously have to , what exactly did you think you would find in there ?
When I said they had to be replaced as a set , yeah there was a good reason for that .

Well initially, in September 2024 when my wife skied the ski in it sounded to me like it was a top end problem with the engine. Not a deep bell sound, but a top end sound.

So, I pulled the engine.

And I spun the midshaft coupler and it was smooth and it spun the impeller just fine.

So, I put the engine on the bench and put a 650 in the ski.

And then when we launched the ski last week, it was kicking up white water but it had no torque, so my guess is that it was spinning the impeller somewhat.

At that point, I thought I well it was pretty apparent to me that there was something wrong with the drive shaft.

And that is what I found. And really what I thought I would find.

But I am sorry that I pulled the 701 61X which runs fine and then put the 650 6MB in and then just pulled it. So definitely a goose chase in my troubleshooting.

Again, as I previously stated I am a rookie making rookie mistakes. And I appreciate you guys helping.

Including you @WFO Speedracer and @kevbo who are pros but also @BennyB who was not afraid to answer my stupid question.

There will be more.

The coupler will still spin the impeller even if it is stripped , but once in the water and under load it won't , usually they make a high pitched squealing sound , you are right a pro would hear it and know what it it was , average Joe probably wouldn't .

*When you take apart the midshaft pay attention on what order the seals and bearings go in*
If you do not have a press, a block of wood and a mini sledge works. When you do the rebuild toss the bearings and shaft in the freezer. Heat up the housing a bit with a heat gun, or leave it in the sun for an hour and the bearings will drop in. Once the bearings are in, leave the bearings and housing in the sun to get hot then the frozen midshaft should slide in with a few love taps. @DylanS offers a bearing coating that he can apply to the bearings ahead of time that will keep them happy for the next 30 years.

Next watch and follow the pump and engine shimming videos a few times to make sure everything lines up correctly. If you need shims @TheBuzzard lives near you and probably has a few thousand shims to choose from. =)