What gears you got?

BW velvet drive at 1.9:1

JDCAVE said:

No. They aren't. Just that the Twin Disc guys like to flaunt it and rest of us are green with envy, grovelling away in the background keeping our mouths shut.....


....snip.....


Jim
Sent from my iPad using Trawler Forum

Click to expand...

I wouldn't be jealous...a lot of BW velvet drives out there doing just fine.

The BW Velvet Drives on the assistance towboats I used to run took more abuse in one season than most trawler guys would put them though in a lifetime. The one on the tow boat I ran only got oil changes probably every 1000-1500 engine hours....still going strong.

Kanzaki KM3P4 2.61:1 bolted to a 56hp Yanmar 4JH3E. Seems just fine at 1,700 hr. This trans has a 'torque limiter' (a slip clutch) on the output flange that is supposed to protect things somehow. Time will tell

Allison MH 20s on my sporty, huge gears, indestructable, only fit DDs. BW Velvet Drives in my trawler 2.91s. Not my favorite gear, kinda light.

Original Allision MH 30 (that's 3:1) behind the original GM 3-71 in Skookum Maru. Which will go first, the trans or the engine? No sign of it happening anytime soon, 60 years, 9,000 hours so far.

I wish there was a trolling valve for it though.

I've got a ZF 25A. Drop centre and a 7 degree down angle, which allowed me to mount my engine level. The gearbox is a bit of overkill for 42hp, but the cost wasn't much higher than the ZF15A suggested by the dealer.

I would have preferred a higher ratio than my 1.98:1 but I was too impatient to wait another 4 weeks for a 2.7:1 to come in. Just had to pitch the prop to suit.

Perkins 6.354 4M w/ BW VD 10-17 2.57:1 at 4600 hrs. Still going...

Hurth 630A 2:1
behind a
Cummins 6BT5.9M

spins 1 3/4" shaft

BW VD at 6000 hours, still going strong, no issues.
Xs:"I would kill for a 6 cyl Gardner. Once you buy one, you have to polish them and once you've done that you need to take it out of your boat and put it in your living room, next to the 1970 Bonneville and the BSA Gold Star."
Out cycling the other day and my old car was about to left turn in front of me. I shouted " Hey, that was my car in 1969!" he "well its mine now" and away he went. 1965 GTO convertible. 389 quad, 4 speed. 345hp, no power accessories, not even power brakes. All power to the rear wheels. I sold mine when it was totally worn out, in about 1972. Would be worth almost as much as my boat if in as good condition as the one I saw.

Twin disc MG509 2.47:1 on Cummins 555's, 2" shafts

nmuir; said:

Cummins 555's

Click to expand...

How many hours on those beasts?

Not exactly sure on the hours as the meters were disconnected at 1,700. My guess is maybe 2,500 - 3,000? Hope is they have many hours left in them as they are non-turbo and run at low revs. Rebuilt injectors last year as a preventative measure. Oil analysis results are great. And you are right - they are beasts!

O C Diver said:

Drop center refers to the output shaft being below the input shaft. The alternative is the two shafts being inline (at the same level).

Ted

Click to expand...

Thanks OC...

ZF / Hurth 220A behind a 6LYTA Yanmar 370 hp.
(Hurth marine is part of ZF and Hurth off hwy is part of Dana

John

Kanzaki KM4A...but not sure what the gear ratio is. The engine, service, and parts manual are all at the boat, but I haven't found any notation of the gear ratio yet.

The PO squeezed the 100hp Yanmar 4JH2-UTE into where a 65hp engine once sat, so I can't get a good look at what the information plate says. Can you decipher it from the photo below or have an educated guess?

Hawgwash said:

How many hours on those beasts?

Click to expand...

If I recall right, those 555's were below square - like 4.5" bore by 4" stroke, which is the opposite of most of the traditional marine diesels which are long stroke/high torque.

Can you comment on any noticeable characteristics or your engines in particular?

nmuir said:

Twin disc MG509 2.47:1 on Cummins 555's, 2" shafts

Click to expand...

I once had a 29' Scotty sport fish with a pair of those. The boat was fast but man it was really loud!

MurrayM said:

Kanzaki KM4A...but not sure what the gear ratio is. The engine, service, and parts manual are all at the boat, but I haven't found any notation of the gear ratio yet.

The PO squeezed the 100hp Yanmar 4JH2-UTE into where a 65hp engine once sat, so I can't get a good look at what the information plate says. Can you decipher it from the photo below or have an educated guess?

Click to expand...

Found this PDF...
http://boatswainslocker.com/customer/boloin/customerpages/resourceitems/B_Transmission.pdf

...where the KM4A ratios are listed as...

1.47:1, 2.14:1, 2.63:1, and 3.30:1

...so until I get a better peek, photo, or rubbing, it looks like it's probably 2.14:1

makobuilders said:

If I recall right, those 555's were below square - like 4.5" bore by 4" stroke, which is the opposite of most of the traditional marine diesels which are long stroke/high torque.

Can you comment on any noticeable characteristics or your engines in particular?

Click to expand...

Not uncommon for V-block engines to use under square bore/stroke ratio. Long stroke means long conrod and distance between head and crank gets pretty far. On a v-block this means a really wide beast, and that cramps lots of installs. So they cheat a bit. Tall is easier to handle than wide.

Nothing really wrong with undersquare, a little more heat loss per displacement. Torque goes up with bigger bore, too, so long stroke is not the only way to do it.

Ski in NC said:

Not uncommon for V-block engines to use under square bore/stroke ratio. Long stroke means long conrod and distance between head and crank gets pretty far. On a v-block this means a really wide beast, and that cramps lots of installs. So they cheat a bit. Tall is easier to handle than wide.

Nothing really wrong with undersquare, a little more heat loss per displacement. Torque goes up with bigger bore, too, so long stroke is not the only way to do it.

Click to expand...

Fascinating, thanks Ski.
Your words make or easy mental pics.

Hurth 630A

Velvet Drive 7000series, 2.66:1' rated for 550 HP, behind 210 HP 6BT5.9M
Haven't seen too many 7000s

single Cummins engine V555M and gear T.D. MG506 @ 2.5:1 with a hair over 6,000 hrs. on them.