Transmission Life Expectancy

How long should I go on my transmission before a rebuild? I have no reason to suspect a problem but with 8000 hours I wonder. Fluid is changed every 200 hours.

It´s a BW model# 10.17.014 behind a FL SP135 which powers a full displacement, single engine vessel so low RPM's.

While you list your city as Friday Harbor (I assume you mean the one here in WA?) your boat is obviously not here. But on the Grand Banks forum the most recommended shop for transmission advice, service, and overhaul is Harbor Marine in Everett, WA. They specialize in BW transmissions. Phone is 425-259-3285. Website is Everett, Washington - Boat Service, Parts, and Supplies : Harbor Marine The contact name mentioned the most is Mike Vogt. I don't know if he is still there.

We have yet to need servicing on our BW Velvet Drives but when the day comes that we do we'll talk to our diesel shop in Bellingham but most likely will enlist the help of Harbor Marine.

Even though your boat is not in the area it might be worth a phone call to see what they have to say about your questions. If they do recommend a servicing they may be able to recommend a shop in the area your boat is that does good work.

Same transmission in my lobsterboat (not pic here) and maybe about 6000 hours since I had it "rebuilt" also 160 SHP and gets run harder than you I'm sure and Lots more shifting and a lot less oil changes. Oh, and this transmission had been run on oily saltwater for maybe 5 hrs at trolling speed.

I replaced my damper plate last year so decided to open and inspect the transmission myself this time having inspected my sons BW direct drive transmission that spring. I did just that and found nothing wrong whatsoever. Every bearing smooth, bushings unworn, gears new looking, friction plates flat, oil pump unworn, and so on. I did relace the gasket, seal, & Oring kit & a few springs I had no spec. to measure them by, and the crush piece between the rear bearings cause it looked to be a one use item.

So I would not expect to find much to look at in your lightly used and well maintained VelvetDrive.

However that said, in 50+ years in boats, I have been dead in the water twice (outboards excepted of course) and both times have been damper plates. Change it when you look at your transmission, listen with your hatch open at no wake speed, & replace it with one that has a "get home" feature.

Sorry to be no help for you Larry but reading you and Brooksie's posts sure make me happy. My BW Velvet Drive was rebuilt 2 years ago by the previous owner. By all accounts it was original to the boat 45 years ago.

One thing that's very enlightening to do is watch the shaft coming out of a marine gear and seeing how long it take to come to a stop when the marine gear is shifted into neutral. Because shifting a marine gear--- at least one like a BW Velvet drive--- when the shaft is still turning can be detrimental to its health.

So one day we lifted a cabin sole panel so we could watch what the shafts did under various conditions.

Our engines idle at 600 rpm. In gear at idle with the boat stationary, the shafts take a second and a half to come to a stop when the shifters are moved from forward to neutral.

At idle with the boat in gear and moving at our idle speed of some 3-1/2 knots, the shafts take three to four seconds to come to a stop when the shifters are pulled to idle.

In gear with the engines running at our cruise rpm of 1650, if the engines are pulled to idle and the shifters are moved to neutral the shafts do not stop until the boat does or nearly so. So they freewheel for a long time.

How knowing this affects our operation is:

At idle rpm with little or no boat movement (maneuvering up to a dock or in a slip) whoever's running the boat waits at least two seconds after putting a shifter in neutral before putting it into gear again.

At idle rpm in gear with the boat moving, say through the marina to our slip or the gas dock, the person driving waits at least five seconds after putting the shifters in neutral before putting them into gear again.

And if we're running at cruise rpm and for some reason have to take the boat out of gear after pulling the engines to idle (we never take a marine gear out of gear with the engines at anything but idle rpm) we do not put a marine gear back into gear until the boat has nearly come to a complete stop.

Obviously every boat will be different. Cutless bearing and packing gland compression on the shaft will have a big effect on how long it takes the shaft to come to a stop when its marine gear is pulled into neutral. But we think knowing how long it takes for the shafts in our boat to stop rotating under the conditions we typically encounter and then making sure we don't shift them back into gear until they do will add significantly to the service life of the marine gears.

We have never found it necessary to saw back and forth with the shifters as we see a lot of boaters do as they try to correct a misjudgment or save a docking. If we've properly planned our approach and judged our speed, drift, turn, etc. correctly, things just don't happen that fast even with a strong adverse wind. Not so fast, anyway, that we can't pause for two or three seconds in neutral before shifting into the other gear.

Are we talking about a Velvet Drive?

Marin said:

... the most recommended shop for transmission advice, service, and overhaul is Harbor Marine in Everett, WA. They specialize in BW transmissions. Phone is 425-259-3285. Website is Everett, Washington - Boat Service, Parts, and Supplies : Harbor Marine The contact name mentioned the most is Mike Vogt. I don't know if he is still there...

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Thanks, I know Mike and he's good. He helped me replace Hobo's Dampner plate and he rebuilt our last transmission. We have no phone service where we are but he is on our call list.

Brooksie said:

...So I would not expect to find much to look at in your lightly used and well maintained VelvetDrive...

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That's what I'm beginning to hear. Here's a response I got from a well respected member on Boatdiesel for the same question:

Input shaft seal. Several high hour machines started leaking there, and leak came on FAST. Seal can be changed without cracking the case, but gear must be pulled from motor. Other than that (and your´s may be fine), the guts should be in good shape. Also seen splines on planetary reduction fail, but those were high hp machines

Daddyo said:

Are we talking about a Velvet Drive?

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Yes.