Bad coupler mercruiser 5.7 ??

TikiHut2

Seems like I have a coupler about to fail in my '04 5.7 Mercruiser. After a 10mi run this week I suddenly heard a rumbling sort of low frequency roar at cruising speed. It seemed like the props were suddenly cavitating and engine revs started to increase a bit as the boat started to fall of plane. I stopped and checked the props for debris or slop or metallic sounds when turned by hand but there was nothing.

Oil levels were fine and the drive wasn't hot but I idled a few miles with no odd sounds. After 20 mins I decided to try and ease it back on plane. Gently pushing it back up all seemed fine until I started to trim the drive out a bit when the roar retruned. retracting the drive to a fully fwd/down position and the rumble disappeared allowing me to limp home at cruising speed. Any attempt to push a bit of trim out would cause the noise to return.

All I can figure is that the engine coupler rubber or spline is about shot and with the drive fully down the splines have a bit of a bite left. I'm not looking fwd to an engine pull and want to be sure I'm on the right track. Anybody have a similar experience with those symptoms?
Thanks, Mike

Black_Diamond

If a coupler fails, you get nothing out. They should not be 'slipping' per se unless it's on some flaky edge of holding in low power. With the noise changing on the drive trim position it sounds more like ujoints.

You'll have to pull the drive to find out any of this. IF you need a new coupler, upgrade to the heavy duty one for a few bucks more, cheap while the engine is out.

http://www.mercstuff.com/couplers.htm

While it is all apart, good time to replace ujoints, etc.

TikiHut2

Agreed. I just had the drive off about 10 hours ago and they looked and felt as tight as a new one. Either way I'll start with the drive of course, maybe even today if I get motivated. It was 82* at dawn so it's roasting outside by 9am and the humidity is off the scale so I'm a bit draggy. It's our version of of an endless winter that you guys endured.

Just the thought of a drive issue is not great news but I'll post as I get into it.

If it's the coupler then pulling the motor isn't a terrible job and I'd have an excuse to replace the oil pan and do some other hard to get at maintenance while I'm at it during my off-season.

frodo13056

Tiki, I hate to disagree with BD but I had a coupler fail when I had my 1988 Rinker 206 with the exact symptoms you described: running along at cruising speed and all of a sudden, the engine reved up and the boat fell off plane. I did the same as you - stopped, made sure I didn't foul the prop, checked everything I could think of, eased the throttle back up and all seemed fine until I started trimming the boat and same thing would happen. I've now seen several couplers fail and the common thread is that there is a god awful smell of burned rubber/grease/gear lube or some combination of those that is a dead give away of a toasted coupler. If you smell anything like that near the back of your engine, you may also see a fine dust that looks like graphite under the output shaft near the coupler. It's not a terrible job to change the coupler but the engine does have to come out to do it. There is a "super duty" type coupler that Al talked about quite awhile ago - can't remember if it's on the old board or it is was on the this forum. Good luck!

TikiHut2

Thanks Frodo. I'll pull the drive today, so we'll see. I didn't open the hatch to smell for rubber but just had it in my head that is was a coupler failing slowly rather than the typical instant ending.

RY, you've been smelling diesel fumes too long. Lol. I guess it beats being snowed in..... but not by much. 4mths of broiling season before my boating season restarts so Ill be in the engine compartment.

Thanks. Mike

TikiHut2

Well off it came and the u joints are perfectly tight the gimbel bearing is absolutly perfect and the inside of the bellows is nice and clean. On closer inspection there's an extra amount of debris around the back end of the coupler.

So unless there's some other magical fix Ill be doing an engine pull to replace a coupler that is probably original '04 so I can't blame it. Im actually impressed it ran another 60mi mostly at cruising speed after the first symptoms.

Pics of the coupler from above and one inside the bellows and one checking the gimbel bearing that's awkwardly reminiscent of an uncomfortable Dr exam..... "this won't hurt a bit....and cough". From here on out those will always be called a gimbel bearing check.

Black_Diamond

Make the upgrade to the HD coupler, not much more money.

TikiHut2

Thanks for the heads up and the link. Definately will.

TikiHut2

I'm having a last second pause before I tear the motor out. It seems to me that there's a clutch of sorts in the upper end of the Bravo III. Could that be slipping during a 20mile or longer run causing the rumbling and cavitation-like reduction in speed. It just seems odd that the coupler would last another 50mi+ after the first symptoms, and that both incidences occurred after running at cruising speed for over 30mins.

Trimming in/out slightly to recreate the noise at speed is the other mystery.

I have the drive off and the hoist set up over the engine but haven't started disconnecting/unbolting anything in the engine bay just yet.

Black_Diamond

Tiki,

 

There is a cone clutch in the upper drive unit, if that's going out I would expect the drive oil would not look/smell good from the slippage.  I'd drain the oil and look for metal shavings or the fine aroma of burnt drive oil.  They (cone clutches) can perform erratically when on their last breaths.

TikiHut2

I'll get a sample tonight. I was almost hoping it was a coupler rather than in the drive.

As for the coupling, there's no real apparent rubber debris or burnt stench to indicate a coupling failure and the shaft spline was completely free of any metal shards that would be expected from a stripped spline.

I've misplaced the link/phone# to the OD guys that had been mentioned here quite often. Anyone have a clue about who to call that might recognize an OD mystery?

Black_Diamond

Www.allamericandriveservice.com

Worth a phone call. A coupler would be cheaper!

jmoen438

Mike, I had the exact same thing two years ago and it was the coupler.

TikiHut2

Thanks J. Yours shook if trimmed a certain way but would still get back on plane with no noise if tweaked just right?

I checked my drive oil for metal and even pulled the top cap but it was perfectly clean so Im feeling pretty confident its not the drive.

The coupler spines look and feel fine as far as I can tell. Pretty sure that the motor comes out tonight.
Thanks. Mike

212rowboat

have you checked your hub, by chance?

TikiHut2

Thanks Drew. Hub\coupler same animal unless Im missing something.

U-joints are another suspect even though they look and feel perfect. Don at all American drives says u can't tell by feel if they are getting sloppy enough to wobble\shake a bit when slightly off angle by trim.

He was adamant about checking drive alignment yearly but no later than every 24mths and completely intolerant of an alignment tool that can't be pulled out with only two fingers in each engine rotation at 90* angles. Thats a really tough standard.

He also spent 30mins diagnosing the drive while I'd wrench to be sure it wasn't something internal. An enlightening discussion on drive issues of all brands filled the gaps. What a great resource and he truly knows his stuff. He works on all drives but really likes the newer VP drives. I wouldn't have guessed but he's up to his elbows in all of them. Mike.

212rowboat

i know nothing about the biii.. the hub i speak of is in the prop, not the engine coupler.. again, i really don't know anything about anything southwest of the crank.. :-)  i'm trying to learn. though..

Black_Diamond

Drew, the B-III props are solid SS, no hub to spin..well not at least without major damage to the drive too.  lol 

The guy at All American Drives is a great resource...he'll talk your ear off about drives   They rebuilt both of mine, handy he's only 1.5 hours from my home.  Small shop but stacked with drives everywhere, even does complete specials for high HP applications.

TikiHut2

Drew. Yeah, Prop hub wasnt on my radar with a B3. The innards of these dual prop drives would be a gearheads paradise. To me its a frightfully complex low tolerance bunch of hyper expensive voodoo. Here's to hoping Im free of my worst fears in a drive failure.

BD. I wish I had a guy this qualified only an hour away. Sorry about your drive trouble but glad you had the right guy so close.

Engine team hits it tonight.

Dream_Inn

Good luck mike and keep us informed. I've sure had enough drive issues lately. Bad voodoo going around. I got myself a kahuna man that is bringing good luck. On our 10day trip now and all is well. I better talk to kahuna now and give him a drink.

TikiHut2

Kahuna and Admiral last week in Ft Myers beach. Their opinion on out drive problems.....rum. I want this guy on my front deck. lol

Somebody here once said, "if we didn't use them they'd never wear out". The fact that things are wearing out hopefully means we're busy using them for all they're worth. This drive drama isn't as painful as some of the folks here have seen lately but every boat dog has his bad-drive day. Lets just hope they're behind you (and BD and Ray and Tony, etc..) for a good long time.

Have a great season, Mike

Dream_Inn

Love the pic Mike!! now I feel kahuna needs a pic here as well. Next time I fill up, drink is getting low, i'll have to take one. You ever get anywhere north you better contact us. Gosh, I've had a lot to drink today.

Glassguy54

It must be brutal to have to work on your boat with out the luxury of an air condtioned shop down there in Sarasota this time of year. I hope you get it all sorted out without too much trouble. I wish I had the confidence to tackle stuff like that on our boat, but I'm afraid I'd screw it up. And I used to work on cars a lot, but they're just too complicated anymore. Stay hydrated! Save the rum for after the engine is out.

raybo3

Mike nice pic of you and the admiral but who is the guy on the left?????? Just kidding bro hope things work out for you with your drive........

jmoen438

Exactly Mike

TikiHut2

Thanks, J. After hearing your scenario I'm almost 100% sure it's the coupler. Thanks.

Yeah G54, Too flamin' hot tnite. Heat index in the shop over 100* at 6pm and only came down to 90* by 11pm. Couldn't muster the work force to climb into the bilge.

Ray, the crusty old cabin boy was allowed to stand in edge of the photo. My gal has a weakness for double fisted Tiki guys with a tan.... but man, that grass skirt is scratchy. lol

raybo3

LOL Mike you crack me up..........

TikiHut2

Ah, the update. Got after it this morning and a few hours later the engine was out and hanging at eye level. Nothing terribly difficult, all the bolts came loose thanks to a few days of soaking with penetrating oil, labeled all the wiring, took pictures of connections and just generally kept moving at a steady pace. Here's the gruesome crime scene.

Looks like the rubber is slipping in the housing. The splines are fine.

Somebody asked about my oil pan re-paint from last fall. Well it looks like this is a condensation issue that everyone should be aware of. I'll re-re-paint.

The Admiral is sizing up the aft cockpit for a hot tub Tiki Zone

And some Bravo 3 top end gear-set p0rn for the hard c0re art lovers. she is in great shape....luckily. Parts are on order so we'll see. Mike

Black_Diamond

Glad it was only a coupler. Did you order the HD replacement?  You might look into POR-15 for repainting. It will seal/stop the rust. 

212rowboat

Man, I'd consider an aluminum pan... They aren't that much more, and likely relieve enough stress to pay for itself... Besides.. it will never be easier than right now... 

TikiHut2

So post a link to what you'd recommend. It's probably time to check the sump screen anyway. Apparently a marine application is baffled to deter oil movement when climbing onto plane and there'd need to be an accommodation for the dip stick accuracy.