Mercruiser stern drive

[tep59]

ok so I purchased a 2008 bravo 3x and it needs u joints, come to find out no one but mercruiser sales them. A deal on them is 240.00 each so I'm thinking about replacing the ujoint assembly with the regular bravo ujoint assembly. Don't need the larger ujoint assembly for my application. Did some research on seals and bearing assembly's and they appear to be the same. So for future ujoint replacement could be done much more reasonable. I'm hoping the yoke that goes into the gear housing is the same internally. Anybody ever heard of the being done are know if it's doable?

 

[Scott Danforth]

Look in the stickies

 

[harringtondav]

If your Merc. U joint is 865496A02, iBoats has a Sierra 18-6406 for $88.57. I buy Sierra U joints for my Alpha II, and they have the same massive trunion size as the Merc. I have no info on Sierra's Bravo U joints, but they cross to the Merc. p/n and I suspect they are built the same and will work just fine, especially since you state you have a lower duty cycle requirement.

Merc. buys their Alpha II U joints from Rockwell, Sierra from Koyo. Again, with a micrometer, the Sierra are built the same and work just fine.

 

[Scott Danforth]

Look in the stickies. Spicer numbers are listed. U-jount under $30

 

[achris]

Look in the stickies. Spicer numbers are listed. U-jount under $30

This is a late model Bravo 3X drive. The unis are not the same as the Alphas, or the 'standard' Bravos...

That said, I have no idea what any of the after market part numbers would be. I would take a uni out, measure it up and then google the life out of it

Chris.........

 

[harringtondav]

Yea, I keep going on with on my U joint phobia. Spicer and others have U joints that will fit out drive yokes, but their cross trunion diameters are puny small compared to Merc. and Sierra U joints. If you don't do full power donuts and hard high power turns, you could be OK. But the marine U joints are designed to live with full power in any condition the operator has the guts to apply.

Go with achris , remove your U joints, and mic. or digital caliper a good trunion journal for size. Buy a U joint that is this size and fits your yokes. I just crossed the Bravo 3x 866136A01 and found Sierra 18-6407 and 18-1711. Just FYI for other options. These will fit your yokes.

 

[achris]

Yea, I keep going on with on my U joint phobia. Spicer and others have U joints that will fit out drive yokes, but their cross trunion diameters are puny small compared to Merc. and Sierra U joints. If you don't do full power donuts and hard high power turns, you could be OK. But the marine U joints are designed to live with full power in any condition the operator has the guts to apply.

Also remember, automotive unis only need to move a few degrees, 'marine' unis in stern drives, are expected to work with full power on up to 55 degrees of movement... And if they let go at full power in a turn, it's not pretty!

Chris.........

 

[tpenfield]

I would imagine that if you do a little Internet 'digging' you can find the OEM parts from the original supplier at a fraction of the Merc/Quicksilver price. Sierra branded parts are fine for the most part, but I do prefer getting the original the Merc buys.

 

[Scott Danforth]

achris , a double cardon joint like that on the shaft of the outdrive is the same double cardon joint parts that is on the front driveshaft of large 4x4's NEAPCO, Spicer, Federul Mogul (Moog, Napa, etc) and GKN all make u-joints

harringtondav there literally are about 250 different series of u-joints in the automotive world, not including Rzeppa joints and other CV styles. that puts it into the thousands. Mercruiser used to buy spicer, they may be buying GKN. not sure who Sierra is buying. to say that marine u-joints are made different is just not so. its just a different series of driveshaft u-joints than what you may be used to.

the Bravo u-joint is the same as early 70's MOPAR from under the 383 powered B-bodies and the 4x4 trucks with Dana-Spicer axles and drive shafts. the funny thing is its the "Small" MOPAR joint (7260) vs the large (7290).

7260 U-joint dimensions: 1.078" cap diameter x 3.250" overall width

7290 U-joint dimensions: 1.125" cap diameter with grooves x 3.625" overall width

BTW, there is a reason many street cars "upgraded" to MOPAR u-joints and driveshafts in the 70's when pushed into drag racing

https://spicerparts.com/resources/measuring-u-joints

the following was borrowed (stolen) from OSO on a bravo u-joint discussion https://www.offshoreonly.com/forums/general-q/337376-bravo-u-joints-older-drive.html

FYI @ all... these also fit the Alpha I Gen II (probably 91-97). That's what I have. Original P/N is the same as Tom's and is a Rockwell part.

From what I've read, the NAPA and Moog are both made by Federal Mogul. The Moog 246 should be the exact same as the NAPA UJ246. Advance Auto has the Moog for $24 and I've never bought anything at AA without a 20-30% off coupon. I'd personally prefer a Spicer U Joint but I can't find those locally and need to install mine tomorrow.

Moog has really disappointed me lately and many say the quality has gone down recently. I agree. I replaced all the front suspension components on my truck with top of the line Moog and had to replace them after only 2 years. If they fail again or if these U joints fail I'll never buy Moog again.

Here's what Rock Auto has that will also fit...

Standard Replacement
GMB 2151307 Info
Rear Shaft All Joints; Lubrication Type Grease Fitting in Bearing Cap; 1.078" Bearing Cap Diameter
* Stocked in outlying warehouse--shipping delayed up to 1 business day
$7.63

GMB 2151306 Info
Rear Shaft All Joints; Lubrication Type Grease Fitting in Cross; 1.078" Bearing Cap Diameter
* Stocked in outlying warehouse--shipping delayed up to 1 business day
$7.63

ACDELCO 45U0117 {#89029299} Professional Info
FitsAt Transmission; w/ 2-1/8" O.D. Yoke
OrAt Rear Axle; w/ 2-1/8" O.D. Yoke
$8.62

MOOG/PRECISION 315G Premium Info One of our most popular parts
FitsAt Transmission; w/ 2-1/8" O.D. Yoke
OrAt Rear Axle; w/ 2-1/8" O.D. Yoke
$9.15

Heavy Duty
ACDELCO 45U0137 {#89029319} Non-Greasable Super Strength; NON-GREASABLE U-JOINT Info
FitsAt Transmission; w/ 2-1/8" O.D. Yoke
OrAt Rear Axle; w/ 2-1/8" O.D. Yoke
$11.12

ACDELCO 45U0120 {#89029302} Greasable Super Strength; GREASABLE U-JOINT Info One of our most popular parts
FitsAt Transmission; w/ 2-1/8" O.D. Yoke
OrAt Rear Axle; w/ 2-1/8" O.D. Yoke
$12.32

MOOG/PRECISION 246 Greasable Super Strength; 1.078" Bearing Cap Diameter Info One of our most popular parts
FitsAt Transmission; w/ 2-1/8" O.D. Yoke
OrAt Rear Axle; w/ 2-1/8" O.D. Yoke
$13.32

MOOG/PRECISION 245 Non-Greasable Super Strength Info
FitsAt Transmission; w/ 2-1/8" O.D. Yoke
OrAt Rear Axle; w/ 2-1/8" O.D. Yoke (Only 4 Remaining)
$14.14

 

[achris]

Scott Danforth Not saying Merc make their own, I know they don't. Just saying the 'thinner' joints, while they would fit in the position, may not have the strength required. By all means, buy aftermarket, but be aware of what exactly you are buying.

Chris........

 

[harringtondav]

Scott Danforth The reason I keep bringing this up is I tried to beat the $60 per U joint game myself. I'd find a compatible U joint with the exact external dimensions as a Merc., but when I pull the needle cap the trunion diameter have always been smaller than my 'marine' Alpha's. Last winter I was still trying and found a Spicer 'M' for marine - same fit up dims. I got hold of an application engineer who pulled the print and said the trunion O.D. is .600". I've mic'd. my Merc. and Sierra Alpha's and theirs is .700". This is 15% less needle bearing area.

Automotive U joints are used in the ends of rear axle drive shafts where the angle correction due to suspension springs my be 10 degrees total. Same for FWD drive shaft Cardan U joint pairs. An Alpha drive turns +- 45 degrees, plus a little more if you're trimmed off neutral when turning.

Those smaller forged 8620, core hardened, case hardened trunions will not break under the torque of the largest big block. There are eight trunions sharing the torque load. But in a hard turn four of those trunions are laying down intermittently, and the torque loads increase dramatically. The breaking strength is still OK, but the needle bearing side loads go thru the roof. And this is is where trunion journal rippling and pitting start, then it's all over.

Machine design engineers resolve higher radial-side loads with larger bearings. Just look at the pair of massive Timken tapered rollers that support the drive's input drive gear. Huge separating forces with the drive pinion. Merc. engineers are doing the same with their drive shaft U joints. I tell people the Alpha can handle up to 300 hp, and ?? ft. lbs. of torque, so the Auto U joints are probably OK for a 3.0L. But I'd be nervous about stretching it much above that, and stick with the Merc. engineer's design intent. Sierra does this at 40-50% of Merc. Still $70/pair over an Auto replacement, but I can think of less critical areas to save that kind of money.

My drive is rebuilt good as new, including a new gimbal brg., and I can hear that low, soft transom moan when I take a half throttle, 25 mph turn. That is when the drive shaft does it's real work.

I'd buy any unis you listed above in a second if I new the trunion cross had the same beef as the 'marine'.

 

[Scott Danforth]

see page 6 http://www.gkngroup.com/offhighwaypowertrain/products/documents/DUJ/GKN-DUJ-Brochure-GB-latest.pdf

 

[Rick Stephens]

I think harringtondav ought to buy anything he wants to buy. And pay whatever premium makes him feel good. But I would bet that 80-90% of the active forum members, over the years, have switched over to alternate sourced u-joints. I did long ago on multiple outdrives. I'm running Moogs right now and only way I'd get much more horses out of my 4.3 would be if it was injected. I can't see worrying too much about that with my application. And I have yet to hear much conversation or stories about catastrophic u-joint failures by all the members over the years that did switch, or even those that didn't. I'm sure it has happened, somewhere, but it seems a windmill too far to tilt against for my tastes.

 

[harringtondav]

Yea, I'll admit I'm cautious. 9 yrs retired after 30+ years as a drive train eng. for a big green Ag. Co. They had a reliability goal of 10,000 hrs full diesel torque use before the customer had to unbutton anything. We boat in 20-30 mile long Miss. river pools, and the last thing I want is to be waving a life jacket on a paddle at a 15 barge tow while I'm dead in the water. So I tend to overkill the reliability.

And yes Rick Stephens , a failing U joint will let you know it's feeling poorly long before it leaves you stranded. Of course the operator has to hear and react to this.

 

[Rick Stephens]

Yea, I'll admit I'm cautious. 9 yrs retired after 30+ years as a drive train eng. for a big green Ag. Co.

I hear you. Most of us pick our battles based on our experiences in life. Speaking of which, my latest experience is the only reason I'm have time to type on a computer - we basically blew up 1/2 million in green stuff on monday. Both our combines had experience points for me, one broke a shaker arm and literally spit the sieve out on the chaff spreader, the other combine, again literally, blew the hydraulic filter off the housing and blew a main hydraulic hose. Replaced those and half hour later, alarms sounded and it repeated the act. No one seems to be able to diagnose the hydraulic issue and the thoroughness of the damage to the interior of the first one is putting it in the intensive care. Nothing beats wheat harvest for wishing the maintenance had been better.

 

[tep59]

Thanks for the replies, my joints are gkn and Sierra says they no longer services the 18-6407 and I haven't been able to get any measurements for the 18-1711 except for a tape measure laid accross the top of a bearing cap pic from a guy on eBay and it appears to be to large, mine is 1.2040, I called a guy at the ujoint store and he said he sold Sierra a bunch along time ago that where the gkn and I suppose sierrSsold out and can't buy anymore. I've googled it to death and can't find any info for a replacement except a web site that appears to be a scam. So that's why I'm considering doing what my original post is about. And I also talked to a gentleman about these joints that does lots of bravo repair and he said merc was my only option. But of course I didn't think to ask him about what I would like to try with the regular bravo ujoint assembly. Thanks

 

[harringtondav]

Nothing beats wheat harvest for wishing the maintenance had been better.

True that. That 10,000 hr. tractor goal isn't designed to happen by itself. The owners manual's maintenance schedule makes it happen, assuming it's followed. Same with our hole-in-the water toys. I firmly believe Merc's out drives will outlast the boat and engine if properly maintained, used sanely, and avoid submerged hazards.

 

[nola mike]

And I have yet to hear much conversation or stories about catastrophic u-joint failures by all the members over the years that did switch, or even those that didn't. I'm sure it has happened, somewhere, but it seems a windmill too far to tilt against for my tastes.

That was the point I was going to make Rick Stephens
. We're talking about u-joints snapping here. I have about a million more likely failure points in my setup. Not including my 2 month old u-joints