Cutlass Bearing Size Chart

Standard cutlass bearing sizes

The chart covers shaft diameters from 3/4" (20 mm) up to 4" (100 mm) across four materials: phenolic (the modern default and our biggest seller), rubber for sandy or silty water, brass-shelled for worn or oversize housings, and GRP for bonding directly into fibreglass stern tubes. Nearly every size follows the standard marine proportion — overall length is four times the shaft diameter — so a 1-1/4" shaft takes a 5" bearing and a 40 mm shaft takes a 160 mm bearing. New to the part itself? Start with what a cutlass bearing is and how water, not grease, keeps it alive.

Cutlass bearing dimensions: three numbers identify every size

Every bearing in the chart is defined by three dimensions: the shaft (inside) diameter, the housing (outside) diameter, and the overall length. Measure the propeller shaft itself and the bore of the stern tube, strut, P-bracket or skeg it fits into — never the old bearing, which may be worn undersize or a past mis-fit. The measuring guide walks through the full method with callipers.

Every cutlass bearing size we stock

How to read the chart

I/D and O/D are published as tolerance ranges rather than single figures, because the fit is engineered into the bearing itself. To confirm a match:

• Your shaft should measure just below the bottom of the I/D range — that gap is the running clearance the water film needs.
• Your housing bore should measure just above the top of the O/D range — the interference fit is what grips the bearing in the tube.
• Never add clearance yourself. Exalto machines the correct clearances in; if your measurements sit inside a published range rather than outside it, stop and re-measure or ask us before ordering.

The part-code prefix tells you the measurement system: M_SF codes such as MPSF50 are fully metric, I_SF codes such as IPSF20 are fully imperial, and MI_SF codes such as MIPSF40 pair a metric shaft with an imperial housing — a common combination where a metric shaft has been fitted into an older imperial stern tube.

Measured your shaft but can't find it?

215 sizes cover the vast majority of shafts in Australian waters, but odd combinations do turn up — reconditioned shafts, worn housings, older imperial tubes. If you're replacing a Johnson Cutless® or another brand, cross-reference by dimensions (I/D × O/D × length), not by part number; cutlass and cutless are two spellings of the same part. Send your three measurements through our contact page and we'll match the right genuine Exalto bearing within one business day. If your housing has worn oversize, a brass-shelled bearing is often the fix.

Cutlass bearing size FAQs

What size cutlass bearing do I need?

Match three dimensions: shaft diameter (I/D), housing bore (O/D) and overall length. Measure the shaft and the housing directly — not the old bearing — and the length will normally be four times the shaft diameter. Our measuring guide shows how.

Are cutlass bearing sizes metric or imperial?

Both. The Exalto range includes fully metric (M_SF), fully imperial (I_SF) and metric-shaft-in-imperial-housing (MI_SF) sizes, and the chart lists every dimension in millimetres and inches.

What if my size isn't in the chart?

Email your shaft diameter, housing bore and length via our contact page and we'll match a genuine Exalto bearing within one business day — including cross-references from other brands, which we do by dimensions rather than part numbers.

Order your size — free Express Post Australia-wide

Found your bearing in the chart? Click through to its product page and order — every price includes GST, delivery is free Express Post anywhere in Australia, and in-stock bearings ordered before 2pm AEST are dispatched the same day (anything not on the shelf ships in 3–4 weeks). Fitting one is a slipway job, so it pays to have the bearing on hand before the boat comes out — see the replacement guide for what's involved.

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