The big gearboxes

Identification

This is a Bonfiglioli MVF63 / VF63 worm-reduction gearbox, from the old Bonfiglioli VF family. The important markings now fit together very well:

Marking -> Meaning

BONFIGLIOLI -> Bonfiglioli Riduttori, Bologna, Italy

VF63 -> Gearbox frame/model size 63

912300701 -> Housing/casting identification number — not a serial number

92 in circular casting mark -> Almost certainly 1992 casting year

Other small circular symbol -> Appears to be a foundry/die/cavity identification mark, not another date

The strongest confirmation is that I found the exact number 912300701 independently associated with a Bonfiglioli unit described as TYPE MVF63/FC, code 203160243. That makes the identification much stronger than simply matching the shape or the VF63 lettering. 

And yes: looking at your new close-up, I agree with you about the circular mark. The center clearly reads 92. This is the characteristic sort of removable date insert used in permanent molds/dies. So I would date the gearbox housing casting to 1992. The gearbox itself could have been assembled in 1992 or shortly afterward. That timing fits extremely well with your early-1990s Lewmar installation.

What “MVF63” tells us

The old MVF63 was an industrial worm gearbox, and Bonfiglioli documentation/interchange data gives some very useful hard numbers. The center distance was 62.17 mm, the standard hollow output bore was 25 mm, gearbox mass about 6 kg / 13.2 lb, and ratios were offered from roughly 5:1 through 100:1. The housing material is listed as aluminium, with synthetic-oil lubrication. 

That ~6 kg number is interesting because a surviving discontinued MVF63/FC-INCH is listed at 13.56 lb / 6.15 kg. Even more interestingly, that particular FC-INCH version is specified as a 19:1 worm reducer. 

So there is a real possibility that the Lewmar version you have is closely related to, or actually is, the MVF63/FC-INCH. I would not yet call your gearbox 19:1 solely from the casting, because the same VF63 housing could be fitted with different worm/wheel combinations. But 19:1 has now become a very credible number to check. One easy test is 19 input-shaft revolutions versus one output revolution.

The historical construction is also quite good. Contemporary Bonfiglioli documentation describes the worm shaft as case-hardened alloy steel with ground tooth flanks, while the worm wheel is phosphor bronze. That agrees perfectly with the parts you’ve been working on — steel worm engaging the bronze wheel. 

The oil quantity is now essentially nailed down too

Bonfiglioli’s actual VF spare-parts documentation specifies 0.320 L of synthetic oil for VF63 — 320 mL, and states that these smaller VF units were factory-filled for life without normal fill/level/drain plugs. The quantity is the assembly fill and applies irrespective of normal mounting orientation. 

That explains something that looked odd on your Lewmar version: no conventional fill plug. What you’ve described — filling through the worm-shaft end after removing the seal/end closure — makes sense for a gearbox whose industrial version was intended to be factory-filled rather than serviced in the field.

So I would now summarize your big Lewmar gearbox as:

Bonfiglioli MVF63 / VF63, housing no. 912300701, aluminium worm reducer, housing cast in 1992, approximately 6 kg, 25-mm-family output geometry, originally synthetic-oil lubricated with about 320 mL, and very likely an FC / inch-output derivative supplied to Lewmar.

The next thing I’d pursue is the exact ratio and the meaning of “FC-INCH”, because I think we’re getting very close to identifying the exact Bonfiglioli configuration Lewmar bought rather than merely the gearbox family.

Upon showing the new markings I found:

Yes — this second gearbox is much more informative, and it confirms several things we were previously inferring.

The markings read:

• MVF 63/P — Bonfiglioli worm gearbox, size 63, P version.
• 2031601020K01 — Bonfiglioli configuration/code number for this particular build. I can’t find that exact old code in current catalogs, so the K01 suffix may indicate an OEM/special configuration.
• 06/93 — production batch/date: June 1993.
• B3 — mounting position.
• 1.5 — this is 1.5 HP.
• 19 — reduction ratio i = 19, i.e. 19:1.

The key breakthrough is an old MVF63/P example I found with essentially the same style of plate. Its bottom row is explicitly labeled HP on the left and i on the right. That gearbox is stamped 1 and 38, meaning 1 HP and 38:1. So your 1.5 and 19 decode very cleanly as 1.5 HP, 19:1. 

The ratio is also independently supported: Bonfiglioli MVF63/P units were definitely sold in 19:1, and a surviving catalog listing describes an MVF 63/P, ratio 19, 25-mm hollow output shaft. 

So we can now describe your Lewmar gearbox quite specifically as:

Bonfiglioli MVF 63/P, code 2031601020K01, manufactured June 1993, B3 mounting, 1.5 HP nominal rating, 19:1 worm reduction.

That is a very nice match for Jedi’s original 1993–94 Lewmar installation.

It also means my earlier thought that your gearbox was “probably 19:1” is no longer a guess — the gearbox itself says 19:1.

And this gives us a useful comparison with the first gearbox: its casting had a 1992 mold-date mark, while this one carries an actual 06/93 production marking. So the first one could very plausibly also have been assembled in 1993 using a housing cast in 1992.