Thamesway Marine Products Ltd

Serial Numbers / MK Nos

Transmission Types

Transmission Prices

Frequent Questions

Useful Information

Fault Diagnosis

D.I.Y. Repairs

Spare Parts Lists.

Engines.

User Boats

Bargain Basement

How To Find Us

HOME PAGE
The Serial No of your gearbox can be found on an Identity Plate which is normally located between the two cooling pipes on the back of the unit.
In the case of the Offset Gearboxes the plate can be found on the vertical surface adjacent to the cooling pipes / or on the Reduction Case near to the filler.
If the Identity Plate is missing, look for a Stamped No on the top rear of the main gearbox. (see below.)
We can normally identify a box from this No.
If this No is also missing, one can identify the Mark No of the box as follows:-
In the case of a Direct Drive box ( picture below) a Mk II box has a one piece backplate and does not have the oil seal casting.

In the case of a Reduction box the Mark No can be established removing the Ahead Cover Plate.(picture below).
The bearing behind the cover will be either a straight roller (MK II box) or a Taper Roller.( MK IV box)

The Serial No on the Identity Plate consists of 3 parts :-
The 1st part identifies the type of gearbox.
The 2nd part indicates the engine for which the box was originally supplied.
The last part is the individual gearbox number.

The 1st part has the form:- letter prefix /number/letter suffix:-
The prefix letter indicates the offset of the box.
The number indicates the Mark of the box.
The suffix letter denotes the Reduction and Output Rotation.

Prefix Letters.
None.....................The box has no offset.
"R"......................The box is offset to the Right.
"L".......................The box is offset to the left.
Numbers.
'11' / '12' / '13' /'15' are early pre Mk 11 units. (Most Spares are available.)
' 17 ' ......Mk11 Box. Right hand engine rotation. ( all spares are available)
' 19 ' ......Mk1V Box. Right hand engine rotation. ( all spares are available)
' 21 '.......Mk IV Box. Left hand engine rotation. ( all spares available )
' 31 '.......Mk IV VEE Drive. Right hand engine rotation ( spares limited)
Suffix Letters.
' A ' .........Direct Drive ( 1:1 ) (Lefthand Prop.)
' Z ' ..........2:1 Reduction / 2 pinion (Right hand Prop.)
' R '..........2:1 Reduction /3 pinion (Left hand Prop.)
' Y '...........3:1 Reduction /2 pinion (Right hand Prop.)
' X '...........3:1 Reduction /3 pinion (Left hand Prop.)

Examples:-
17Z /......./....... = MKII 2:1 Reduction.
19A /....../....... = MKIV Direct Drive
R19R/..../........ = MKIV Right hand offset /3 pinion