Many marine transmissions rely on a floating spline coupling arrangement to transfer power from the engine flywheel to the transmission.

The relatively short spline on the transmission input shaft, coupled with the spline in the drive plate, is the weakest link in your boat’s drive system. This spline arrangement is highly intolerant to poor alignment and is very susceptible to wear from constant changes in engine output (e.g. commercial fishboats operating at low RPM), vibration and inconsistent off-on loading conditions.

The Suredrive™ is designed to eliminate this weak link by locking a female center spline hub onto your existing transmission input shaft.

It is not necessary to replace your input shaft even if the spline is worn. The Suredrive™ center spline hub will lock onto even the most worn spline surfaces.

Do not let a saleperson sell you an input shaft if yours is worn, you only need 20% remaining on your spline for a Suredrive to engage and lock 100%.

Don't let the noise of damper plate failure scare your fish away.

Durable elastomers (rubber inserts) are installed at the perimeter of the inner spider drive to aid in dampening engine vibration and torsional forces, thereby providing a much quieter drive system.

Finally, the outer spider drive is bolted onto the engine flywheel. The center sockets of the outer spider engage the inner spider drive with the rubber inserts effectively cushioning the mating surfaces.

Velvet Drive 73C worn input shaft solution


In the BorgWarner family of marine transmissions the C73 is an icon for strength, slim physical size and is known for its velvet smooth operation.

However, the C73 was discontinued from production. The popular transmission has carried on servicing the owners for many hours of operation in commercial as well as pleasure boat applications. Unfortunately, in all great products there is often a short coming. In the C73 it is the input shaft spline related problem that has put many of these transmissions out of commission. The spline engagement between input shaft and driveplate spline is subjected to extreme conditions which is common to this type of drive input into the marine transmission of similar arrangement.

Just to mention some of the severe contributing factors of the spline wear:

  • engine torsional vibration
  • very heavy spline loading due to relatively small spline diameter
  • splines are operating without lubrication of any kind and in a harsh marine environment.

Needless to say, the input shaft splines will wear beyond serviceable condition. There have been many attempts made to restore the worn spline, ultimately this effort proved unsuccessful! The lack of replacement input shaft planetary carrier unit left the owner/operator with no other option but to replace the C73 with another currently used transmission. This expensive undertaking is not necessary for those vessels which are still equipped with the C73 transmission.

NextWave Marine Systems offer a solution that restores the transmission to a more reliable state than has been with the original spring type driveplate (with out any expensive and major attempts to fix the worn input spline).

The solution is the Suredrive™! This unique drive coupling unit has the capability to lock onto a worn spline as long as there is a trace of spline left on the shaft. NextWave will assure your safety and peace of mind that your propeller will be connected to the engine power. This will eliminate the weakest link in the marine propulsion system that has plagued the owner/operator for a very long time. The small marine vessels with the loosely fitted male and female spline connection will ultimately fail and leave you ‘dead in the water.’

The largest North American Distributor has informed us that there are still some thousands of C73 Marine transmissions in service. There are no lack of repair parts except for the input shaft. This major component is rendered unserviceable due to the worn spline and there is no other reason. To extend the service life of the C73 indefinitely, the Suredrive™ is the only drive coupling that locks onto worn transmission input splines and in turn restores reliability of the propulsion system, which will also save this fine marine transmission from the melting pot.