{"product_id":"castair-p3b775sk","title":"Castair P3B775SK","description":"\u003cp\u003eThe Castair P3B775SK is a 3-groove (3B) motor pulley with an SK taper-lock hub and 7.75\" outer diameter. Three B-section grooves allow this pulley to drive three matched belts simultaneously, which is appropriate for compressor motors in the 3-7.5 HP range where two belts cannot reliably handle the drive torque. The SK hub means you need a separately ordered SK bushing to mount this pulley to your motor shaft — but that also means the same pulley can serve different shaft diameters simply by swapping the bushing.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eNote: Cast Air did not provide a dedicated manufacturer product page for this pulley.\u003c\/strong\u003e Specifications are drawn from the product listing and standard 3B SK-hub pulley engineering conventions. Contact us before ordering to confirm SK bushing size for your shaft diameter.\u003c\/p\u003e\n\n\u003ch2\u003e3B SK-Hub Motor Pulley — What You Need to Know\u003c\/h2\u003e\n\u003cp\u003eThis pulley is at the intersection of two sizing decisions: groove count (3B) and hub style (SK taper-lock). The 3-groove configuration handles higher motor torque than 2-groove systems. The SK hub provides installation flexibility — one pulley works with multiple shaft diameters depending on which SK bushing you install. The 7.75\" OD sits in the mid-to-upper range for Cast Air 3B pulleys, producing a specific drive ratio that determines pump RPM. If your original motor pulley matches these three parameters — 3B, SK hub, 7.75\" OD — this is the replacement part.\u003c\/p\u003e\n\n\u003ch3\u003ePulley Specification Details\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eGroove Profile:\u003c\/strong\u003e 3B (three B-section V-belt grooves)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHub Type:\u003c\/strong\u003e SK taper-lock (bushing required, sold separately)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOuter Diameter (OD):\u003c\/strong\u003e 7.75\"\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApplication:\u003c\/strong\u003e Motor-side pulley for belt-drive air compressors, mid-to-high HP range\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatibility:\u003c\/strong\u003e Castair belt-drive compressors using SK-hub 3B motor pulleys and B-section belts\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e P3B775SK\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhy Three Grooves on a Compressor Motor Pulley?\u003c\/h2\u003e\n\u003cp\u003eAs motor HP increases, so does the torque that must be transmitted through the belt drive. Two B-section belts have a practical power limit — beyond that limit, belts slip (especially on startup under load), run hot, and wear quickly. Three belts spread the load across three grooves, reducing per-belt tension and extending belt life while reliably delivering the motor's full output to the pump. Three-groove systems are the standard on Cast Air compressors from approximately 3 HP upward and on any application where startup torque is high.\u003c\/p\u003e\n\n\u003ch3\u003eSK Taper-Lock Hub — Installation Overview\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eOrder the correct SK bushing for your motor shaft diameter separately (common sizes: 1-1\/8\", 1-3\/8\", 1-5\/8\")\u003c\/li\u003e\n\u003cli\u003eSlide the bushing onto the motor shaft, align the keyway, and hand-thread the mounting screws through the pulley into the bushing\u003c\/li\u003e\n\u003cli\u003eTorque mounting screws evenly — the taper draws the bushing and pulley together into a tight, concentric fit\u003c\/li\u003e\n\u003cli\u003eTo remove: back the screws out and thread them into the jack holes — this pushes the taper apart and releases the assembly without damage\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhen Does a Shop Need the P3B775SK?\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eOriginal 3-groove SK-hub 7.75\" OD motor pulley is cracked, worn, or damaged\u003c\/li\u003e\n\u003cli\u003eMotor replacement where the pump and flywheel are 3-groove design and the original SK bushing can be reused\u003c\/li\u003e\n\u003cli\u003eRebuilding a higher-HP Cast Air compressor to original drive specifications\u003c\/li\u003e\n\u003cli\u003eBelt slippage is occurring on a 3-belt drive and the pulley groove wear has been identified as the cause\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eCast Air 3B Motor Pulley Size Comparison\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eP3B615SD — 6.15\" OD — $105.88\u003c\/strong\u003e — smaller OD, SD hub, lower pump RPM relative to motor speed\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eP3B775SK — 7.75\" OD\u003c\/strong\u003e (this unit) — mid-to-upper OD range, SK hub\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eP3B838SK — 8.38\" OD — $132.83\u003c\/strong\u003e — larger OD, SK hub, highest pump RPM in the 3B SK series\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e P3B775SK\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Cast Air (Castair)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eGroove Type:\u003c\/strong\u003e 3B (three B-section V-belt grooves)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHub Type:\u003c\/strong\u003e SK taper-lock (bushing sold separately)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOuter Diameter:\u003c\/strong\u003e 7.75\"\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBelt Section:\u003c\/strong\u003e B-section (three matched belts)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrice:\u003c\/strong\u003e Contact for current pricing\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer Data:\u003c\/strong\u003e Product page not available — specifications from product listing data\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhat Is Included\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e1x Castair P3B775SK motor pulley (SK hub)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eSK bushing and three B-section matched belts are not included. Specify your motor shaft diameter and drive center distance when you call so we can help you source everything in one order.\u003c\/p\u003e\n\n\u003ch2\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h2\u003e\n\u003cp\u003eA 3-groove SK-hub drive system has more moving parts than a simple fixed-bore single-belt setup — and getting the bushing size, belt section, and belt length right matters. We have been selling Cast Air parts since 2016 and can walk you through the complete component list for your specific compressor. Free shipping on all orders, free tech support, and full manufacturer warranty.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eCast Air specialist\u003c\/strong\u003e since 2016\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFree shipping\u003c\/strong\u003e on all orders\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFree tech support\u003c\/strong\u003e — we help you source the complete drive system\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eFull manufacturer warranty\u003c\/strong\u003e\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSystem-level sourcing\u003c\/strong\u003e — pulley, bushing, and belts in one order\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eCall 866-217-0063 for quick answers and help!\u003c\/strong\u003e\u003c\/p\u003e","brand":"Cast Air","offers":[{"title":"Default Title","offer_id":53342573986005,"sku":"P3B775SK","price":0.0,"currency_code":"USD","in_stock":true}],"url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-p3b775sk","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}