NXT1 Transmission won't go in Forward; goes in Reverse and Neutral fine.
Makes no strange noises.
First noticed had drive lever Forward, but no forward thrust. It was resisting going into forward some with the lever, sometimes have to push harder than I'd like, but then it worked again, and drove fine.
Then, it would not go in Forward again (lever forward no thrust), then it would, then finally it won't go in Forward (lever moves forward properly, at Transmission it's in "forward position" but gears not engaging. Reverse, neutral are Fine.

I pulled the trans Friday.
Gears and fluid look fine, no shavings or dirt. Goes in Reverse fine (drives output shaft one way, other way it Freewheels; must be the design), neutral fine (freewheels both ways), Forward it freewheels both ways, but then sometimes "catches" and drives forward, but my hand on output shaft not able to provide much force, it clearly "slips" or isn't "all the way in gear" or something.

Parts Diagrams (I have no association with any business, just for reference)
http://www.perfprotech.com/mercruise...240?model=2049
http://www.perfprotech.com/mercruise...250?model=2049

The Transmission COVER and shifter mechanism seem "ok" to me:
The Yoke ("shifter fork") has minor wear on its lower facing where it contacts the inner "center" of the Clutch.
The Shifter Cams (wedge shaped cams on both sides of the Yoke) have minor wear on their ramp-like faces; apparently they have slight "detents", they are not a "pure wedge shape".

The TRANSMISSION looks good, gears and fluid fine, gears look to have ~NO wear on them.
The wear is on two brass rings "Sleeve, 3.75 with 20 thread" on both sides of the clutch, that the Yoke and Shifter Cams presses on to do the Shifting.
The edges have some slightly burred brass, and the one toward the Tailshaft is "unscrewed" some, so you can see 4 threads showing, while the OTHER brass ring shows fully screwed down, maybe half a thread showing.

The brass rings are interesting, they are not perfectly symmetrical on the side face, facing those cams; there is a slight "H+" mark on the "higher" (more inward built up brass) and a "1-" mark on the "lower" or less built up brass section; both brass rings have this ,and they meet up H+ across from 1- as they contra-rotate (constant mesh with the drysump/connecting gear down below).

I was told BEFORE I took it out, by a kind person on this website that the problem WOULD be that one of the Brass Rings had backed off and I would see the bare threads, and this makes it not go into Forward Gear, and if I can screw that down again and lock-tite it so it doesn't unscrew (changing it if it's bad), it would fix the problem and the trans would work again. Said he had this happen to his.
Voila, that's what I see, that one rearward brass ring unscrewed "inward" toward the Yoke; and this IS the brass ring pressed upon by the "Forward Shifter Cam" when trying to put it in Forward.

My curiosity is that with it "unscrewed" it goes further INWARD, so I'd think it would be "pushed even MORE in Forward Gear", not LESS. I must not understand the clutch's mechanism fully yet.

Updated: I ordered A SERVICE/REPAIR MANUAL for NXT1 Transmissions! Lakematdude in message below found the details on proper manual that INCLUDES NXT1 trans, THANKS!

I know there are businesses who repair these and owe us nothing, and I'd like to use them, but I am not rich; I have this thing looking at me, haven't pulled the guts on the trans apart yet--
but if I can do this "Brass Ring Sleeve Unscrewed Repair" myself, the day would no doubt come when there is some repair I CAN'T do and whoever kicks in with the Knowledge here, we all can know as a good player out to help ALL of us, and by their Help, Ye Shall Know Their Goodness

I did one Repair Step By Step on SSM6 hydraulic trim line change:
http://www.offshoreonly.com/forums/d...ne-change.html
maybe I can do one on this too

SO: Can I pull this apart, change those 2 sleeves=brass rings ($196.22+shipping), screw them all the way tight with Loctite, reassemble and my Port NXT1 Transmission be good to go without bending over? Or, is the Clutch bad too?
Thanks for any help! And, advice on best reasonable repair shop to send it to, if it isn't able to be done by me for whatever reason (is it too complex, need strange special tools, etc).

There is no secret in obtaining an service manual, It's knowing what info that can be found inside the service manual that could be a little challenging to know before buying one though. As you can see below, section 7 covers the Transmission. Glancing over it, it's pretty detailed and an absolute "must have" for how far you are into it. Hope this helps, good luck.

MERCURY RACING Service manual #15, Merc part number 90‑8M8020285 covers Dry Sump NXT¹ SN 0M954570 – 2006–

Manual Outline
1 - Important Information
A - Drive Identification and Maintenance
B - Troubleshooting
2 - Removal and Installation
A - Sterndrive Unit and Transom Assembly
3 - Upper Drive
A - Upper Drive
4 - Lower Drive
A - Lower Drive
5 - Transom
A - Transom Assembly
6 - Power Trim
A - Remote Trim Systems (Single-Ram)
7 - Transmission
A - Transmission
8 - Drive Cross-Sectional Supplements
A - Critical Component Positions and Information

lakematdude: Thanks for the reply! your searching is better than mine, getting all that detail on what that manual includes.
I have ordered it 2 day air to get here Weds, hope to tear trans down Thursday if all goes well!

Still, somebody/s knows the answer to my issue ahead of time, KNOWS the trans, and has seen it multiple times and fixed it...it's just helping a fellow boater out with the info, not Dragon's Treasure jealously defended?
Friendly American Know-How and Garage Mechanics Unite?

I've got one stuck in forward, shops telling me it needs $6,000 worth of parts?!

yeah that is my fear, someone digging into it and suddenly between parts and service it runs up ridiculous.
You can get a brand NEW one for $6999 best price I've seen so far, so at 6K just get a NEW one.
Mine is FINE but for no forward and no WAY it takes much to fix it.

Send me new info for $6,900 if you have it. Thanks!

[ATTACH=CONFIG]504096[/ATTACH]
Xwing, the threads showing on the reverse gear is common. Take a look at where the inside taper meets the brass and see if there is a gap.

The trans shifts just like a bravo. The brass rings have a hi/lo side on them. When you put it in forward the cam on the shift fork rotates and is bumped by the hi side of the ring on the reverse gear. This moves the clutch into the forward gear.

The shaft & the clutch have a spiral on them. As soon as there is a little bit of drag on the clutch and it tries to rotate the spiral forces the clutch against the inside taper portion of the gear. The angle of the taper is "self locking". So once together it does not want to come apart. And due to the spiral the more you twist it the harder it is pushed together. To shift into neutral the shift fork/cam is rotated the other way, now the cam on the side of the forward gear is bumped by the forward ring, and if all is good it will release the clutch from the taper.

But 2 things can go wrong. If there is not enough friction initially to get it to move and then lock the spiral does not push on it. The other is that for one reason or another (high RPM shift, maybe getting a little too much air when running) the clutch gets stuck in the gear. Sometimes it will pretty much weld itself in, sometimes you can pop it loose in a press.

Your case sounds like not enough friction. It is possible your clutch is worn out. You can also try some valve grinding compound on the clutch & gear to give it a little help engaging, just make sure to clean it completely and don't go too crazy with it.

Eddie, $6000 is a lot, but it is possible. We just quoted one today that needs $4700 worth of parts.

In any case when they work they work well and they are small & light. But SO expensive to fix.

Please excuse the shameless & completly self-serving plug here, but that is why we came up with our kit to allow a conventional transmission to fit without re-rigging the boat.

http://www.cyborgtransmissions.com/C...yborgNEXT.aspx

Marc: THANKS for your explanation!
It makes sense, in that when it was IN gear, it would take FULL power, full throttle, no slippage.
It was just getting it INTO gear, it seemed not to want to go in and ENGAGE, or at idle speeds it would "pop out" of gear or something; then, it just wouldn't GO in forward gear anymore.

It sounds like I could change the clutch and the 2 brass "shift cam bumping" rings that show some wear, and hopefully do ok.
I saw your neato Cyborg trans setup before I wrote all this, looks great, but that would be a lot MORE money for me, not less so...Repair Of NXT1 Here I Come.
If I can't do it, you might very soon get a nearly brand new looking NXT1 needing a couple parts to Git 'Er Done...boating season in Wisconsin is very short

UPDATE: trans out and disassembled.
Found one "Bearing Assembly" Part # 19 on NXT1 parts diagram, Merc #31-861792, a flat faced radial needle bearing, that sits next to nesting spring that is on clutch, has fractured off half of its face, so you can see the radial needle bearings on half of it.
The Forward Gear inner aspect that takes the Clutch's friction is worn a bit unevenly, one spot with some slight grooves.
The Clutch is somewhat worn but not flattened all the way on its friction surfaces.
The brass "Sleeves" that are screwed onto the Forward and Reverse gears are worn, but not loose or backed off. The brass Sleeve on Reverse Gear is worn more (that is what bumps the trans into Forward, so since Forward was the problem, probably part of the issue not going into gear).

The rest all looks fine, gears look like new except the friction face on inner aspects.
I am changing the Clutch and Forward and Reverse Gear assemblies (includes the brass rings), and both of the Bearing Assemblies that sit next to the nesting springs.

The reverse gear is still good; can be re-used in the future with a new brass ring, but I couldn't get the brass ring off of it. It is assembled with Loctite 680, which has 4000psi shear strength; and is fine threaded so almost welded on. My buddy who works at a large company shop is going to try to remove it, have to heat it to 250C and remove while hot. Then I can re-use that gear in the future with a new brass ring installed.

The forward gear could probably be re-used but with the slight galling ridges on one spot where clutch engages I am concerned it will not be perfectly round, may heat and wear improperly and thus fail early.
At $1347 for forward and $530 for reverse gears (discounted from $1810 and $670!) I was sure hoping NOT to change the gears but since it's out just going to play it safe. At least the little bearings are only $22 each.
The Clutch was $637.
Clean it all out, new oil, and hopefully good to go.
Labor so far is free LOL

UPDATE 2: The trans is back in and works beautifully so far

I put in the 2 new radial bearings that go against the nesting springs; a new forward and reverse gear; and new clutch.

The OLD gears' brass ring "sleeves" that screw onto the Forward and Reverse gears had to be MACHINED off, they would not come off otherwise.
The reverse gear is definitely re-usable, and I have the brass rings to put on it.
The forward gear is fine but for its worn slightly unevenly inner "friction" surface, but that is the critical surface (the "gear" part is only used for reverse and driving the drysump oilpump!)

So, now I can rebuild NXT1 transmissions at least that far hope I don't have to do it again!! LOL.
Thanks to all for the help/guidance.
Now to swap out the high pressure fuelpump on the way out popping fuses...