According to the official Thamesway Marine Products DIY Guide , every teardown requires a fresh set of consumable components: Gearbox Component Direct Drive Models Reduction Box Models TM 12020 x 1 TM 12020 x 1 Output Oil Seal TM 12470 x 1 TM 12436 x 1 Transfer Shaft Seal TM 12436 x 1 Gaskets & O-Rings Complete Kit Complete Kit Neutral Brake Pad TM 12016 x 1 TM 12016 x 1 Oil Filter TM 12009 / TM 12773 TM 12009 / TM 12773 Specialized Workshop Tools

Before starting any work, identify your specific model using the serial plate usually located on the top of the gearbox. Thamesway Marine Products Model Variants

The TMP’s two separate oil compartments are a frequent source of confusion. This section of the manual is vital. The upper box contains the forward/reverse gearing, while the lower box (the reduction box) is for the reduction gears.

Use standard SAE 30 engine oil . Do not use multi-grade oils (like 10W-40) or modern ATF unless explicitly stated for a specific sub-variant, as multi-grades degrade friction coefficients and cause the hydraulic clutch to slip.

Test shifting at low RPM, then progressively higher. 7. Where to Find the Top TMP Gearbox Workshop Manuals

The system operates at approximately 95 to 100 psi . Flicking pressure gauges often indicate low oil levels.

resulting from a clogged internal oil filter (MK II / MK IV styles).

Because TMP is not a mainstream brand, here is the :

Crucially, standard TMP gearboxes are calibrated for right-hand (clockwise) rotating engines. However, specific variations built for Ruston Hornsby or Coventry engines feature a modified internal oil pump to accommodate opposite rotations. These specialty units feature a serial identification code starting with . Always verify the model number on the identification plate located at the rear of the box before ordering components from the Thamesway Marine Products Spare Parts List . 2. Essential Maintenance & Fluid Requirements

While the Thamesway Marine manual is the primary source, several other "top" resources can enhance your repair experience.

This has left a legion of boat owners asking the same question:

Wash all components in a non-flammable cleaning solvent. Blow them completely dry using compressed air. Do not wipe parts with shop rags or paper towels , as stray lint can clog the microscopic channels of the high-pressure hydraulic valve block.

: Found on specific Ruston Hornsby or Coventry engines. The internal oil pump runs in reverse, requiring a dedicated, specialized pump assembly. 2. Output Configurations