XL Shaft Only – Why Every Model Requires Extra Long Outboards?

Views: 0 Author: Site Editor Publish Time: 2026-07-29 Origin: Site

Inquire

Meta Description: All our aluminum RIBs require XL (extra long) shaft outboards – 25 inches. Learn why standard or long shafts cause cavitation, poor fuel economy, and dangerous handling.

Target Keywords: XL shaft outboard, extra long shaft vs long shaft, outboard shaft length guide

The Non-Negotiable Rule

Every aluminum RIB we build – from the 520 to the SP1150 – requires XL (extra long) shaft outboards (25 inches / 635mm).

We do not make exceptions. We do not offer "standard shaft" transoms. If your outboard dealer tries to sell you a long shaft (20") or standard shaft (15"), stop them immediately.

Here is why.

What Happens with the Wrong Shaft Length?

If you mount a standard (15") or long (20") shaft on a 25" transom:

Problem	Consequence
Cavitation plate too high	Propeller sucks air from the surface. Loss of grip.
Ventilation in turns	Engine over-revs. Boat loses thrust mid-turn. Dangerous.
Poor hole shot	Takes forever to plane.
Fuel waste	Propeller loses bite. Burn 20–30% more fuel.
Porpoising	Boat bounces rhythmically at speed. Uncomfortable and unsafe.
Overheating	Water intake may not stay submerged at speed.

If you mount a long shaft on a 15" or 20" transom (not relevant to our boats, but for context):

Lower unit hits underwater obstacles

Excessive drag

Poor handling

The correct shaft length is not optional. It is basic marine engineering.

Why Do Our RIBs Need XL Shafts?

Two reasons:

Deep deadrise (24°–26°) A sharp V hull places the transom higher relative to the waterline than a flat-bottom boat. The propeller needs to reach deeper water to stay gripped.
Large tube diameters (530mm–600mm) Our tubes are large and buoyant. They lift the stern higher at rest and at speed. A standard or long shaft prop would be dangerously close to the surface.

Result: The vertical distance from our transom top to the propeller's ideal depth is exactly 25 inches – XL territory.

Compatible Outboard Brands (XL Shaft Models)

All major brands offer XL (25") shaft options on most models above 50HP:

Brand	XL Shaft Availability
Yamaha	Standard on 60HP+ (F70 and up)
Mercury	Standard on 75HP+ (FourStroke and Pro XS)
Suzuki	Standard on 70HP+ (DF70A and up)
Honda	Standard on 60HP+ (BF60 and up)
Tohatsu	Standard on 60HP+