I have a 1978 Slickcraft with a Mercruiser 302 engine with a TR outdrive and I believe it has a Velvet drive on it, but it has a transmission in it that has a separate lever for forward and reverse. No shift cables. When you switch from forward and reverse a mechanism rotates clockwise and counterclockwise to shift it in and out of gear. The engine runs fine in idle, but as soon as you put it forward or reverse the engine dies. Does anyone have any idea? Does it have a shift interrupter switch like a Alpha Drive or cable system?

Sounds like a Merctrans, there is no shift interrupt.

I would start by trying to turn the propeller by hand (engine off of course) or pull the drive altogether. Could be the drive has failed.

I sent you a PM a while back looking for a part, didi you get it ??

Sorry , i probably read it from the house and completely forgot when I got to the office. I just replied

Email is always better for me, I check that constantly and can set reminders

Like Marc said, the TRS drive does not have a shift interrupt like an Alpha. It sounds like you have the electric shift Merc trans. Like Marc said, try turning the prop by hand. If you can not then most likely the drive has failed and locked up. I had it happen to me when I lost gear fluid.

The electric shift option for the MercTrans II, was intended for controls to be a long way from the drive.

The Merctrans engages forward by using hydraulic pressure to clamp the main shaft discs. This provides a straight through no reduction power transfer. Though total power is limited by the amount of clamping force on the clutches.

Reverse is engaged by a clamping a different portion of the planetary gearset, spinning the output shaft the opposite way. This trans is very weak on Reverse, and needs to be gently used if possible. No on plane and hard reverse hits.

The electrical shift system does have issues, in that it can put the trans into a partial forward or reverse position, with lower than normal hydraulic pressure on the forward plates. This will cause then to slip...generate heat. This trans can not take much heat. 2 liters of fluid, and no real heat sink, less the small water cooler at the bottom.


The TRS input shaft yolk for the Merctrans is also very weak, and a fracture point on impacts etc.