Inspect the planet gear shafts and bushes. Excess wear or clearance play in the planet gears directly causes a severe loss of system oil pressure and loud howling noises during operation.

Symptom: Transmission jumps out of third gear under load. Standard manual advice: Replace shift fork. Top manual truth: The manual reveals a hidden bulletin—a worn detent spring guide bushing. The "Top" guide shows how to drill a 2mm oil relief hole in the bushing. This permanent fix is not listed anywhere else.

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

: The unit has a very small oil capacity; the difference between the "fill" and "full" marks on the dipstick is minimal. Common Issues :

Weighing roughly , the full assembly is an awkward, heavy unit that does not easily lend itself to casual DIY projects. Complete disassembly requires a clean, structured mechanical workshop environment.

Before cracking open your toolkit, you must identify your specific transmission configuration. The TMP Type 12000 was built under several brand names over the decades—including Thames Marine Propulsion, Henry Meadows, Nicor Marine, Bybrook Engineering, and BRB Precision Engineers—before stabilizing with Thamesway Marine Products in 1982. Technical Specifications & Range