Marine Trader BW Transmission troubles

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Nov 17, 2007
Vessel Name
My Yuki
Vessel Make
1973 Marine Trader 34
My 73 Marine Trader is beginning hiccup when I shift into forward.* It'll catch, but only when I increase RPM's to over 1000 once in gear.*Reverse will operate normally. This happens when cold as well as after running a while, so I doubt it's a cooling problem, tho that's something I'll also address when we try to* fix the main problem. *** Lehman 120 with BW Velvet Drive, haven't been able to read the ID plate to get specific model#.

The boat has about 4,000 hours on it and prior to my acquisition 3 years ago the maintenance history is "sketchy". ** I have had fluids, filters etc serviced each spring by a pro while my mechanical learning curve gets going, and I've already checked fluid level, cable travel* (even disconnected them to manually throw the shift lever as far as it'll go).

Given the hours, symptoms, etc.* I am assuming I need to have someone look at a replace/rebuild of the transmission.* Does anyone have advice on possible alternatives?

Also, I'm about 6 hours cruise from my preferred yard.* Does this job typically require haulout of the boat, or can experienced mechanics pull/replace while the boat's in the water? ? Is there a great risk of further damage or complete loss of the transmission if I try to run it to the yard?*
I doubt you'll need to replace the transmission. You may not even need to have it rebuilt. It may be that there is a fairly simple internal linkage that needs to be adjusted or possibly replaced. The fact that it operates just fine in reverse seems to indicate that the basic drive components are okay.

There is a copy of the BW manual on the Grand Banks owners site if you don't have your own copy. It may contain some clue as to what might be causing the problem you are experiencing.

You do not have to haul the boat to have work done on the transmission, or even to remove it.* The shaft is simply disconnected and slid back which will provide sufficient clearance to lift the transmission out if that becomes necessary.* Some installations use engine mounts on the front of the engine and on the transmission.* Others, like ours, have all the engine mounts on the engine.* If your boat has the rear engine mounts on the transmission, it will be necessary to support the rear of the engine before the transmission can be removed.

*And if the transmission is removed, it will be necessary to check the alignment of the shaft and engine/transmission after the transmission is replaced and adjust it as necessary.

As to whether it is potentially damaging to run your boat to the yard six hours away, I would call American Diesel and ask.* While they know everything there is to know about Ford Lehman engines, since so many of them have been bolted to Velvet Drive transmissions I suspect they know a lot about them as well.* Or call a reputable transmission shop and pose your question.

-- Edited by Marin on Thursday 13th of August 2009 04:53:17 PM
Sounds like the forward clutch plates are slipping, maybe that the pump is faulty and not producing enough pressure until it is spinning faster but it is more likely your plates are worn or burnt/shiny. *Generally will need pulling from the boat but parts are readily available for these gears and not too expensive - one of the few smaller gears that are well worth rebuilding. *You may do more damage to it by using it, is the oil still clear and does it run any hotter than usual? *Two people can lift these gears fairly easily and it can be put in a car to take to a workshop.
I am with Phuket on this. I have never repaired a marine gear but it is built with most of the same components as a lift truck transmission- of which I have rebuilt bucket loads. The fact that reverse is working fine shows that the oil pump and pressure regulator are working fine. *Forward will have signifigant more wear than reverse. This wear can reduce the friction plate thickness's. That means that the piston that squeezes these discs together has to travel further before that happens. The seals around this piston can become hardened and worn also. Speeding up the engine produces more oil volume. This increased volume reaches a point where it overcomes that leakage enough to still compress the discs. Eventually the amount of pressure on the discs is not enough to keep it from slipping. Steel discs overheat and warp. Friction*discs get damaged. Oil in marine gear gets contaminated. All the makings of a catastrophic failure. At this stage the repair may only need the normal wear items. Discs, seals, and gaskets. The pistons, pump, clutch drums, bearings and shafts should still be reusable.Steve
You may not be able to slide your shaft back far enough to get the trans off of its splined connection to the engine if you have limited clearance between your prop and the rudder, or if there is a donut zinc on the shaft too close ahead of the cutless bearing. If you can slide the shaft back far enough, the trans will fall off of the back of the engine and lift out quite easily.
When I did mine, a line around the trans and up to a 4x4 laid across the opening in the floor of the salon helped take the weight and make it a one person job (I was younger then, now I would want a second person around as it is a heavy brute.) It was definitely a two man job putting it back in, as you need to line it up perfectly on the splines while holding its whole weight in a very awkward position. While you have it out, check your damper plate. If any of the little springs are gone, it needs replacement.
All good replies you've been getting. It's apparent that rebuilding is going to be more than you will be comfortable with doing yourself. Asking how to get it out means you probably want to pay someone to do it and you be a helper or watcher. Just my impression of your post.

You've done the right things by making sure the lever was going all the way in gear, the fluid was clean and full and the annual maintenance. 4000 hours is a fine lifespan when you don't know how well it was maintained previously.

The transmission will come out with the boat in the water. Even if the shaft will not slide back far enough to allow the trans to slide out you can unbolt the rear engine mounts, loosen the front mounts and lift the engine/trans assy high enough to clear. Typically it will pivot on the front mounts enough to clear.

By all means if the drive plate has not been replaced recently do it now. 4000 to 5000 hours is an average lifespan. All but 30 minutes of the labor is already done when you have the trans out. Don't even think about not doing this one. (IMHO)

My long distance diagnosis is that the trans simply has wear in the clutch discs and perhaps some bearings are getting tired, replace them while it's apart. Clutches, bearings, and seals are dirt cheap, the mechanic rebuilding it is expensive and since he has all the parts out and is putting them back together anyway.......... Don't save $200.00 on parts and have to do this job again. I'm sure he'll lead you down that path anyway.

Hire a local mechanic to pull the trans, or pay transportation for your favored mechanic to come to where the boat is. 6 hours by boat is 1 hour by road? Money well spent.

Continuing to run the boat while in this condition can overheat drums and bearings. Best to bite the bullet and get it done now.

My opinion only, yours may vary, but I have a sheepskin on the wall that says I know how to turn wrenches. ($64,000 question, What does NIASE stand for?)

National Institute for Automotive Service Excellence
Ding, ding. ding. Our first contestant is the winner. Back in 1977 what is currently called ASE was the NIASE, a national mechanic certification program. My apprenticeship group took the tests to help validate the "new" program which virtually every car dealership and independant garage uses today under the name ASE, the orange and blue signs.

Probably more information that you didn't really care about, but.......

Thanks for all the input.* After further investigation, turns out my local mechanic, who handles routine maintenance for me, will pull the transmission, and there is a local transmission shop that's apparently an expert at BW Velvet Drives.*

You all are right, this was NOT a job I'd planned to tackle myself.* The only reason I thought about taking to a yard was my thought that the boat would need to be hauled. Since this isn't going to be the case, now all I need to do is sit back and open the checkbook.
That strategy always works. The question becomes the size of the checkbook! Mine has shrunken significantly over the years since I got into boating!
Fortunately I was working on American iron so the questions weren't foreign to me. And, after taking the other required tests all along during the apprentiship, it was just another test and not a big deal. I can see where working with foreign cars might be a problem.

If you turned the test upside down, did the electrical test questions match the Lucas systems you worked on?

If that BW needs any hard parts you might look at a new ZF. The 63 series can be had for less than $2500
I don't know why I was thinking British for Porsche. Must have been in the sun too long that day. I'll have 2 warm beers from my Lucas fridge as pennance.

Lucas has actually been a division of Phillips for many, many years. In their defense, we bought a Range Rover new in 1991 and still have it. While it has been the most reliable and trouble-free vehicle I have ever owned (a list that includes BMWs and Ford pickups) the only electrical and electronic items on it that have failed and needed replacing have been German-made.

I also bought a Land Rover new in 1973 and still have it. While it is a very simple vehicle, its electrical components are all Lucas and the instruments are all Smiths. In 36 years, I have never had an electrical problem with the vehicle.

I also had an Austin-Healey 3000 MkII in college for awhile. It, too, never had an electrical problem or failed to start in the time I owned it. The only electrical problem I had was the electric overdrive, which would sometime engage and sometimes not.

The brother of my high school girlfriend in Hawaii had an MG-TD (which back then was just a used car--- no real value to it). He'd let us use it for dates and I don't recall that it ever missed a beat.

The British electrical system is a popular target for jokes but at least in my experience it's been way overblown. I had friends in the 1960s and 70s with Triumph TR-3s and 4s, MG-As and Bs, Austin Minis, Morris Minors, Jaguar XK-120s, E-Types, and sedans, and even a few people with Morgans. They all seemed about as reliable--- or unreliable--- as the American cars of the same period. It was not until Toyotas and Datsuns started showing up that reliability was elevated to a whole new standard.
While we're on the subject, how about Lucas' attempt at electronic ignition. I believe it was called OPUS. It was used on almost everything English. MGs Triumps Jags Rolls-Royce and Bentleys. They all failed. The cure was a CD ignition with a Lucas label. Open it up and it had a Declo module in it.*Or how about Lucas' attempt at electronic fuel injection. I remember the V-12 Jags with petrol vapers in the distributor cap igniting when you tried to start the car Those 12 cyl caps were expensive. Made good clock faces though.
Whatever happened to the BW tranny?
IF I got stuck replacing a tranny , Twin Disc (fine used or rebuilt) would be my only choice.

HOWEVER the Hurth although really light duty and needs to be selected 2 sizes bigger than their reccomendation, DOES allow a tranny to be operated cont in reverse , should that be needed to use a particular engine.

For a trawler going cruising the T-D would be only choice , but for coast work the Hurth can solve some problems.
Took the BWs out on Rollsdoc and replaced them with ZF-63As. Bought 2 of them for the price of a rebuild on 1 BW. The A model is a 8 degree down angle. Now my engines are near level (for a boat) The ZF uses the same damper plate and bolts up to the BW housing.*I know of one boat that removed the TDs as switched to ZFs as they were very unhappy with them. I know several boats that switched to the ZFs with no complaints to date.
"I know several boats that switched to the ZFs with no complaints to date."

Try to get a tranny part in under a couple of months.
Update:* the transmission's back in the boat, shifting smoothly, even repainted Lehman red.* Virtually all internal components -- pump/seals, etc are new.

Parts & labor under $2k, and the least expensive rebuilt unit out there was about $3k plus labor.* I feel fortunate that local labor and repair shop resources are available at probably less-than average prices.**

All the diagnoses you folks provided were right on.* Here's hoping I run trouble free for a little while at least!

-- Edited by ARoss on Thursday 24th of September 2009 08:13:20 AM
Excellent!Thanks for the update. Sounds like you got a great deal too.
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