{"product_id":"1760559840-1bd8c7da","title":"ARCO Pulleys","description":"\u003cbr\u003e\u003cbr\u003e\u003cbr\u003ePulley Type\u003cbr\u003eOD (mm)\u003cbr\u003eBore (mm)\u003cbr\u003eGrooves\u003cbr\u003eHub to Groove Center(s) (mm)\u003cbr\u003eNotes\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e6G K Pulley\u003cbr\u003e49\u003cbr\u003e17\u003cbr\u003e6-rib\u003cbr\u003e—\u003cbr\u003eStandard pulley\u003cbr\u003e\u003cbr\u003e\u003cbr\u003eDV V-Belt Pulley\u003cbr\u003e81\u003cbr\u003e17\u003cbr\u003e2 (3\/8\" or 1\/2\")\u003cbr\u003e13.5 (1st), 30.5 (2nd)\u003cbr\u003eLarger diameter dual-groove V-belt\u003cbr\u003e\u003cbr\u003e\u003cbr\u003eDV V-Belt Pulley\u003cbr\u003e71\u003cbr\u003e17\u003cbr\u003e2 (3\/8\" or 1\/2\")\u003cbr\u003e22 (1st), 41 (2nd)\u003cbr\u003eMore offset dual-groove V-belt\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e6G K Pulley\u003cbr\u003e60\u003cbr\u003e17\u003cbr\u003e6-rib\u003cbr\u003e5.6 (1st groove)\u003cbr\u003eSlightly larger than standard\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e6G K Pulley\u003cbr\u003e64\u003cbr\u003e17\u003cbr\u003e6-rib\u003cbr\u003e8.6 (1st groove)\u003cbr\u003eMid-size 6-rib\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e8G K Pulley\u003cbr\u003e65\u003cbr\u003e17\u003cbr\u003e8-rib\u003cbr\u003e8 (1st groove)\u003cbr\u003eHigher output applications\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e10G J Pulley\u003cbr\u003e53\u003cbr\u003e17\u003cbr\u003e10-rib (J)\u003cbr\u003e—\u003cbr\u003eCompact, high-rib density\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e \u003cbr\u003eThe outer diameter (OD) of a pulley directly affects the rotational speed (RPM) of the alternator or accessory it drives. Here's how it works:\u003cbr\u003eBasic Relationship:\u003cbr\u003e\u003cbr\u003eLarger OD pulley → slower alternator RPM\u003cbr\u003eSmaller OD pulley → faster alternator RPM\u003cbr\u003e\u003cbr\u003eThis is because the pulley acts as a gear: the engine crankshaft turns the belt, and the belt turns the alternator pulley. The ratio between the crankshaft pulley and the alternator pulley determines how fast the alternator spins.\u003cbr\u003eExample:\u003cbr\u003eIf your engine crank pulley is 150 mm and your alternator pulley is:\u003cbr\u003e\u003cbr\u003e50 mm → alternator spins 3× faster than the crank\u003cbr\u003e75 mm → alternator spins 2× faster\u003cbr\u003e\u003cbr\u003e⚠️ Why It Matters:\u003cbr\u003e\u003cbr\u003eToo small a pulley: Alternator may overspeed at high engine RPMs, risking damage.\u003cbr\u003eToo large a pulley: Alternator may undercharge at idle or low RPMs.\u003cbr\u003e\u003cbr\u003e \u003cbr\u003eHere’s how different alternator pulley outer diameters (ODs) affect alternator RPM, assuming a crankshaft pulley OD of 150 mm and engine speed of 3000 RPM:\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e\u003cbr\u003eAlternator Pulley OD (mm)\u003cbr\u003eAlternator RPM\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e49\u003cbr\u003e9184\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e60\u003cbr\u003e7500\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e64\u003cbr\u003e7031\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e65\u003cbr\u003e6923\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e71\u003cbr\u003e6338\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e81\u003cbr\u003e5556\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e \u003cbr\u003e\u003cbr\u003e\u003cbr\u003e\u003cbr\u003ePulley Type\u003cbr\u003eBelt Type\u003cbr\u003eGroove Shape\u003cbr\u003eCommon Use\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e\u003cbr\u003eDV\u003cbr\u003eDual V-belts\u003cbr\u003eDeep V\u003cbr\u003eMarine, industrial, legacy systems\u003cbr\u003e\u003cbr\u003e\u003cbr\u003eK\u003cbr\u003eSerpentine (3.56 mm rib spacing)\u003cbr\u003eMulti-rib\u003cbr\u003eAutomotive, marine, high-load\u003cbr\u003e\u003cbr\u003e\u003cbr\u003eJ\u003cbr\u003eSerpentine (2.34 mm rib spacing)\u003cbr\u003eNarrow multi-rib\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e","brand":"ARCO","offers":[{"title":"Dual V-Belt \/ 8 \/ 71mm","offer_id":41789824368725,"sku":"PULL0011","price":39.98,"currency_code":"USD","in_stock":true},{"title":"Dual V-Belt \/ 8 \/ 81mm","offer_id":41789824401493,"sku":"PULL0012","price":57.98,"currency_code":"USD","in_stock":false},{"title":"J \/ 10 \/ 54mm","offer_id":41789824434261,"sku":"PULL0017","price":32.98,"currency_code":"USD","in_stock":true},{"title":"K \/ 6 \/ 49mm","offer_id":41789824467029,"sku":"PULL0007","price":30.98,"currency_code":"USD","in_stock":true},{"title":"K \/ 6 \/ 60mm","offer_id":41789824499797,"sku":"PULL0013","price":52.98,"currency_code":"USD","in_stock":true},{"title":"K \/ 6 \/ 64mm","offer_id":41789824532565,"sku":"PULL0014","price":58.98,"currency_code":"USD","in_stock":true},{"title":"K \/ 8 \/ 65mm","offer_id":41789824565333,"sku":"PULL0015","price":30.98,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0599\/3614\/5493\/files\/pull0011_95x95_2x_11001406-f3e7-4291-8edb-dcf839d27063.avif?v=1761970621","url":"https:\/\/www.pypermarine.com\/products\/1760559840-1bd8c7da","provider":"Pyper Marine","version":"1.0","type":"link"}