Reverse Thrust - Torque needed in O/B Engine

[denfors]

I am use to running various outboards engines on a recreational basis,
but wonder which engine models/types (expect to run twins)- have
the best reverse mode.

The commercial operation - I'll be running is pulling heavy mooring
lines from a commercial tanker vessel or other type (rope and/or wire
lines) mainly in reverse from the vessel hand-off to a mooring dolphin.

The engine strength in reverse is as important, if not more than in
the forward mode.

I realize that most engines are not designed to turn high RPMs in reverse,
but are some better suited than others ?

The boat is a 23' Aluminum Hull (workboat) - Mon Ark (Sea Ark) type -if
you know the model - no engines currently, it previously ran twin 115 HP Yamahas, but was not used in this type operation - reverse pulling power.

Rgds, Dennis

 

[Silvertip]

Re: Reverse Thrust - Torque needed in O/B Engine

What you probably need more than any specific engine, is a prop that is designed for barge/tug/pontoon work. Most prop manufacturers have four blade "elephant ear" props that have a more uniform blade shape with large blade area. Props by their nature are designed for forward thrust and therefore are much less effective in reverse. Large diameter (must fit the gearcase) four blade, low pitch designs should work well in your application.

 

[Silvertip]

Re: Reverse Thrust - Torque needed in O/B Engine

After a couple of adult beverages, what might work is to install a left hand rotation prop intended for a twin installation, on a right hand engine. That would obviously limit forward speed and your control box would work backwards but that's what you want. Reverse throttle throw is typically limited by the control box. Therefore with a left hand prop you would have full throttle capability moving in reverse which is actually forward. (YIKES -- I'm even getting confused!) That creates an operator issue that would certain cause some consternation if someone unfamiliar with the rig were to operate it but you asked for ideas.

 

[tashasdaddy]

Re: Reverse Thrust - Torque needed in O/B Engine

the older J/E handles on controls are reversible, you use cables long enough that the control can be mounted with the cables coming out the front, vs the back, convert the handle, then technically when you move the handle back the boat goes back. this is using the left hand prop, as Silvertip mentioned.

also think using a longer than normal shaft would put the prop below the hull, to get more push, rather than thrust against the hull.