{"title":"Yanmar 4-Stroke 20-27HP Marine Engine Parts","description":"\u003csection id=\"hero\" style=\"padding:16px; border:1px solid #e5e7eb; border-radius:8px;\"\u003e\n  \u003cp\u003eThis page supports Yanmar 4‑Stroke 20–27 HP marine engines and helps you quickly find compatible parts and service information. Below you’ll find maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse the main Yanmar collection for a wider selection. Scroll to the bottom to start browsing parts for this engine, and remember you can use the “Filter \u0026amp; Sort” controls on the collection page to narrow results by horsepower, year range, and part category\/section.\u003c\/p\u003e\n  \u003cp\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/yanmar\" style=\"display:inline-block; padding:10px 14px; background:#0ea5e9; color:#fff; text-decoration:none; border-radius:6px;\"\u003eBrowse All Yanmar Parts\u003c\/a\u003e\u003c\/p\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"identify-model\" style=\"padding:16px; max-width:900px;\"\u003e\n  \u003ch2\u003eHow to Identify Your 20–27 HP Model\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eNameplate location: Look for the metal ID plate on the engine block or rocker cover area; some installations also have a serial decal on the heat‑exchanger or flywheel housing.\u003c\/li\u003e\n    \u003cli\u003eModel code basics: Yanmar small diesels commonly use series codes like 3YM20 or 3GM30. The prefix indicates cylinder count\/series (e.g., “3YM”), and the number approximates output. Option codes may note transmission type (shaft vs. saildrive).\u003c\/li\u003e\n    \u003cli\u003eYear and configuration: Suffixes and plates can indicate production year and emission stage. For saildrive boats, the drive model (e.g., SD20\/SD25) is separate from the engine model.\u003c\/li\u003e\n    \u003cli\u003e4‑Stroke identifiers: Look for a separate engine oil filter, raw‑water pump on the front\/side of the engine, and a belt driving the freshwater circulation pump and alternator.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"engine-overview\" style=\"padding:16px; max-width:1000px;\"\u003e\n  \u003ch2\u003eEngine Overview\u003c\/h2\u003e\n  \u003ch3\u003eYM Series (e.g., 3YM20)\u003c\/h3\u003e\n  \u003ctable style=\"width:100%; border-collapse:collapse;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eFeature\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eDescription\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eConfiguration\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eInline‑3, naturally aspirated, mechanical injection 4‑stroke diesel; freshwater cooling with heat‑exchanger; raw‑water pump driven at the front.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eCommon Models\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003e3YM20 (≈21 HP). Often paired with shaft drive or SD20\/SD25 saildrive.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eAdvantages\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eCompact footprint, good fuel economy, simple routine service, widely supported parts.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eNotes\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eFilters and belts are model‑specific; raw‑water pump brand\/size and anode styles vary by installation. Saildrive service parts differ from shaft‑drive configurations.\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\n  \u003ch3\u003eGM Series (e.g., 3GM30)\u003c\/h3\u003e\n  \u003ctable style=\"width:100%; border-collapse:collapse; margin-top:12px;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eFeature\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eDescription\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eConfiguration\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eInline‑3, naturally aspirated, mechanical injection 4‑stroke diesel; heat‑exchanger cooled with raw‑water pump.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eCommon Models\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003e3GM30\/3GM30F (≈27 HP). Seen with shaft or saildrive options.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eAdvantages\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eProven design, robust mid‑range torque, large service network.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eNotes\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eCooling components (impeller size, thermostat housing) and exhaust elbows vary by year and installation; verify by serial and model plate.\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"service-kits\" style=\"padding:16px; max-width:1000px;\"\u003e\n  \u003ch2\u003eRoutine Maintenance \u0026amp; Service Parts\u003c\/h2\u003e\n  \u003cp\u003eIntervals below are general guidelines for small Yanmar marine diesels; always follow the official service manual and your vessel’s maintenance schedule.\u003c\/p\u003e\n  \u003ctable style=\"width:100%; border-collapse:collapse;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eItem\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eInterval*\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eRemarks\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eParts Link\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eEngine oil + oil filter\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eEvery 100–150 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eWarm engine before draining; pre‑fill filter if recommended; use marine‑grade diesel oil.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/yanmar-oil-filters\"\u003eYanmar Oil Filters\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003ePrimary fuel\/water separator\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eInspect every 50 hours; replace 100–200 hours\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eDrain water bowl frequently; carry spare elements onboard.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/yanmar-fuel-filters\"\u003eYanmar Fuel Filters\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eOn‑engine fuel filter\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eEvery 250 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eBleed air after replacement per service manual.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/yanmar-fuel-filters\"\u003eYanmar Fuel Filters\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eRaw‑water pump impeller\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eEvery 200 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eReplace sooner if weak telltale, overheating, or after dry‑run.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/water-pump-impeller-rebuild-kits\"\u003eWater Pump Impeller Rebuild Kits\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eAir filter \/ intake screen\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eInspect 100 hours; replace 200–300 hours\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eKeep intake clear; replace if oil‑soaked or deformed.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/yanmar-air-filters\"\u003eYanmar Air Filters\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eAlternator \/ water‑pump belt\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eInspect 100 hours; replace 200–300 hours\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eCheck tension and glazing; carry a spare onboard.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/belt\"\u003eBelts\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eZinc anodes (HX, saildrive)\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eInspect monthly; replace at ~50% loss\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eUse correct alloy for your waters (zinc\/aluminum\/magnesium).\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/anodes\"\u003eAnodes\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eSaildrive gear oil (if equipped)\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eEvery 100–200 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eMonitor for water intrusion; renew sealing washers as needed.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/yanmar-service-maintenance-kits\"\u003eYanmar Service \u0026amp; Maintenance Kits\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n  \u003cp style=\"font-size:12px; color:#6b7280;\"\u003e*Intervals are typical recommendations. Always confirm requirements for your exact engine and installation.\u003c\/p\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"common-parts\" style=\"padding:16px; max-width:900px;\"\u003e\n  \u003ch2\u003eFrequently Used Parts Categories\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eRoutine Service: \u003ca href=\"https:\/\/seasierra.com\/collections\/yanmar-service-maintenance-kits\"\u003eYanmar Service \u0026amp; Maintenance Kits\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eFuel System: \u003ca href=\"https:\/\/seasierra.com\/collections\/yanmar-fuel-filters\"\u003eYanmar Fuel Filters\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eCooling System: \u003ca href=\"https:\/\/seasierra.com\/collections\/water-pumps\"\u003eWater Pumps\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eElectrical \/ Starting: \u003ca href=\"https:\/\/seasierra.com\/collections\/starters\"\u003eStarters\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eGaskets \u0026amp; Seals: \u003ca href=\"https:\/\/seasierra.com\/collections\/yanmar-gaskets\"\u003eYanmar Gaskets\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eExhaust Components: \u003ca href=\"https:\/\/seasierra.com\/collections\/yanmar-elbows\"\u003eYanmar Elbows\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eCorrosion Protection: \u003ca href=\"https:\/\/seasierra.com\/collections\/anodes\"\u003eAnodes\u003c\/a\u003e\n\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"troubleshooting\" style=\"padding:16px; max-width:1000px;\"\u003e\n  \u003ch2\u003eCommon Symptoms \u0026amp; Quick Checks\u003c\/h2\u003e\n  \u003ctable style=\"width:100%; border-collapse:collapse;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eSymptom\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eCheck First\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eRelated Parts\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eWeak telltale or overheat alarm\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eInspect intake screen and seacock, check raw‑water pump impeller and cover wear, verify thermostat operation, look for collapsed hoses.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eWater pump impeller kit, pump cover\/plate, thermostat, hoses, anodes.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003ePoor acceleration \/ power loss\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eCheck fuel quality, drain separator, replace filters, confirm clean air filter, inspect exhaust mixing elbow for soot\/salt buildup.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eFuel filters, air filter, injectors, exhaust elbow\/gasket.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eHard starting or rough idle (cold)\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eBleed air from fuel system, test glow plug circuit, verify battery condition and cranking speed.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eFuel filters, glow plugs\/electrical items, starter and belt.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eGearcase noise or milky gear oil (saildrive)\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eCheck oil level\/condition; look for water intrusion and leaking prop‑shaft seals; inspect anodes.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eLower unit seal kit, anodes, gaskets\/sealing washers.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eCoolant loss \/ high freshwater temperature\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eInspect belt tension, circulation pump leaks, heat‑exchanger for scale, and hose clamps.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eBelts, water pump, gaskets, hoses.\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"faq\" style=\"padding:16px; max-width:900px;\"\u003e\n  \u003ch2\u003eFAQs\u003c\/h2\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eAre parts interchangeable between different years or series?\u003c\/summary\u003e\n    \u003cp\u003eSome service items (filters, belts, anodes) overlap within a series, but details can change by year, emission stage, and installation (shaft vs. saildrive). Always verify using the exact engine model, serial number, and drive type.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhen should I replace the raw‑water impeller?\u003c\/summary\u003e\n    \u003cp\u003eAs a preventive measure, replace annually or every 200 hours—sooner if the telltale weakens, the pump has run dry, or you find vane fragments in the strainer or heat‑exchanger.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow often should saildrive gear oil be changed?\u003c\/summary\u003e\n    \u003cp\u003eTypically every 100–200 hours or annually. Inspect for water intrusion (milky oil). Renew sealing washers during service and address leaking shaft seals promptly.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat information do you need to confirm part compatibility?\u003c\/summary\u003e\n    \u003cp\u003ePlease provide the engine model (e.g., 3YM20 or 3GM30), serial number, year (if known), and whether you have a shaft drive or saildrive (model). Photos of the nameplate and the existing part help ensure a precise match.\u003c\/p\u003e\n  \u003c\/details\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"cta\" style=\"padding:16px; border-top:1px solid #e5e7eb;\"\u003e\n  \u003cp\u003eReady to find parts by horsepower, year, and model? Browse the main Yanmar collection to filter and sort the catalog for your exact setup.\u003c\/p\u003e\n  \u003cp\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/yanmar\" style=\"display:inline-block; padding:10px 14px; background:#0ea5e9; color:#fff; text-decoration:none; border-radius:6px;\"\u003eShop Yanmar Parts\u003c\/a\u003e\u003c\/p\u003e\n  \u003cp style=\"font-size:12px; color:#6b7280;\"\u003eIf you’re unsure about your model, send us a photo of the nameplate and the part you need and we’ll help verify compatibility.\u003c\/p\u003e\n\u003c\/section\u003e","products":[{"product_id":"alternator-belt-fits-yanmar-2gm20f-3gm30f-replaces-yanmar-25132-003700","title":"Alternator Belt for Yanmar 2GM20F and 3GM30F Fresh-Water-Cooled Marine Engines – Replaces 25132-003700","description":"\u003csection\u003e\n\u003c!-- 🔧 Table Styles (include only once per page) --\u003e\n\u003cstyle\u003e\n  .ss-table-wrap { overflow-x:auto; -webkit-overflow-scrolling:touch; }\n  table.ss-table { width:100%; border-collapse:collapse; min-width:640px; }\n  table.ss-table th, table.ss-table td {\n    padding:10px 12px; border:1px solid #e5e7eb; text-align:left; vertical-align:top;\n  }\n  table.ss-table th {\n    white-space:nowrap;\n    word-break:normal;\n    letter-spacing:normal;\n    font-weight:600;\n    background:#f8fafc;\n  }\n  @media (max-width:480px){\n    table.ss-table th, table.ss-table td { padding:8px 10px; font-size:14px; }\n  }\n\u003c\/style\u003e\n\n\u003ch2\u003eProduct Details\u003c\/h2\u003e\n\u003cp\u003eThis aftermarket \u003cstrong\u003ealternator belt\u003c\/strong\u003e is listed for Yanmar 2GM20F and 3GM30F marine inboard engines equipped with fresh-water closed cooling systems. It is supplied as one individual replacement belt, not as a kit.\u003c\/p\u003e\n\u003cp\u003eThe belt is listed against the following Yanmar OEM reference numbers: \u003cstrong\u003e25132-003700\u003c\/strong\u003e, \u003cstrong\u003e123325-77360\u003c\/strong\u003e, \u003cstrong\u003e145613-77350\u003c\/strong\u003e, and \u003cstrong\u003e123325-77440\u003c\/strong\u003e. Confirm the number on your existing belt or engine parts documentation before ordering.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eApplication:\u003c\/strong\u003e Alternator belt for fresh-water-cooled, closed-cooling configurations.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePart type:\u003c\/strong\u003e Marine engine belt.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSupply format:\u003c\/strong\u003e One replacement belt.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eReplacement use:\u003c\/strong\u003e Intended to replace the listed OEM-reference belt numbers when the engine application matches.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003ePart Number Matrix\u003c\/h2\u003e\n\u003cp\u003eThese are the OEM reference numbers listed for this belt. Number listings do not replace confirmation of the complete engine application and cooling configuration.\u003c\/p\u003e\n\u003cdiv class=\"ss-table-wrap\"\u003e\n  \u003ctable class=\"ss-table\" aria-label=\"Part Number Matrix\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth\u003eBrand\u003c\/th\u003e\n        \u003cth\u003eOEM Reference Number\u003c\/th\u003e\n        \u003cth\u003eApplication Note\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYanmar\u003c\/td\u003e\n        \u003ctd\u003e25132-003700\u003c\/td\u003e\n        \u003ctd\u003eAlternator belt reference\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYanmar\u003c\/td\u003e\n        \u003ctd\u003e123325-77360\u003c\/td\u003e\n        \u003ctd\u003eReference number listed for this belt\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYanmar\u003c\/td\u003e\n        \u003ctd\u003e145613-77350\u003c\/td\u003e\n        \u003ctd\u003eReference number listed for this belt\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYanmar\u003c\/td\u003e\n        \u003ctd\u003e123325-77440\u003c\/td\u003e\n        \u003ctd\u003eReference number listed for this belt\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eEngine \u0026amp; Model Compatibility\u003c\/h2\u003e\n\u003cp\u003eThe company application listing identifies this belt for the following Yanmar Marine Inboard models with fresh-water closed cooling. The listing does not specify a universal year range, serial-number range, shaft configuration, or horsepower range.\u003c\/p\u003e\n\u003cdiv class=\"ss-table-wrap\"\u003e\n  \u003ctable class=\"ss-table\" aria-label=\"Engine and Model Compatibility\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth\u003eBrand\u003c\/th\u003e\n        \u003cth\u003eEngine Model\u003c\/th\u003e\n        \u003cth\u003eCooling Configuration\u003c\/th\u003e\n        \u003cth\u003eFunction\u003c\/th\u003e\n        \u003cth\u003eOEM Reference Numbers\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYanmar Marine Inboard\u003c\/td\u003e\n        \u003ctd\u003e2GM20F\u003c\/td\u003e\n        \u003ctd\u003eFresh-water cooled, closed cooling\u003c\/td\u003e\n        \u003ctd\u003eAlternator belt\u003c\/td\u003e\n        \u003ctd\u003e25132-003700; 123325-77360; 145613-77350; 123325-77440\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYanmar Marine Inboard\u003c\/td\u003e\n        \u003ctd\u003e3GM30F\u003c\/td\u003e\n        \u003ctd\u003eFresh-water cooled, closed cooling\u003c\/td\u003e\n        \u003ctd\u003eAlternator belt\u003c\/td\u003e\n        \u003ctd\u003e25132-003700; 123325-77360; 145613-77350; 123325-77440\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eTechnical Specs\u003c\/h2\u003e\n\u003cdl\u003e\n  \u003cdt\u003eProduct Type\u003c\/dt\u003e\n  \u003cdd\u003eMarine alternator belt\u003c\/dd\u003e\n  \u003cdt\u003eCooling-System Application\u003c\/dt\u003e\n  \u003cdd\u003eFresh-water cooled models with closed cooling\u003c\/dd\u003e\n  \u003cdt\u003eCompatible Engine Models\u003c\/dt\u003e\n  \u003cdd\u003eYanmar 2GM20F and 3GM30F\u003c\/dd\u003e\n  \u003cdt\u003eOEM Reference Numbers\u003c\/dt\u003e\n  \u003cdd\u003e25132-003700, 123325-77360, 145613-77350, 123325-77440\u003c\/dd\u003e\n  \u003cdt\u003ePackage Format\u003c\/dt\u003e\n  \u003cdd\u003eSingle belt\u003c\/dd\u003e\n\u003c\/dl\u003e\n\n\u003ch2\u003eWhat’s in the Box\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cspan style=\"color:#d0021b;\"\u003e1 x\u003c\/span\u003e Alternator belt\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003col\u003e\n  \u003cli\u003eTurn the engine off, allow it to cool completely, and disconnect the battery.\u003c\/li\u003e\n  \u003cli\u003eConfirm that the replacement belt matches the removed belt and the applicable OEM reference number.\u003c\/li\u003e\n  \u003cli\u003eLoosen the alternator pivot and adjustment fasteners as required by the engine service procedure.\u003c\/li\u003e\n  \u003cli\u003eNote the belt routing around the crankshaft, water-pump, and alternator pulleys before removing the old belt.\u003c\/li\u003e\n  \u003cli\u003eRemove the old belt and inspect the pulley grooves for corrosion, damage, contamination, or unusual wear.\u003c\/li\u003e\n  \u003cli\u003eInstall the new belt in the original routing and ensure it is fully seated in each pulley groove.\u003c\/li\u003e\n  \u003cli\u003eAdjust belt tension according to the engine manufacturer’s service specifications. Do not rely on a generic tension value when a model-specific specification is available.\u003c\/li\u003e\n  \u003cli\u003eTighten the adjustment and pivot fasteners to the applicable service-manual specifications.\u003c\/li\u003e\n  \u003cli\u003eReconnect the battery, start the engine, and verify that the belt tracks smoothly without abnormal noise or vibration.\u003c\/li\u003e\n  \u003cli\u003eStop the engine and recheck the belt installation and tension after the initial run-in period.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eMaintenance \u0026amp; Troubleshooting\u003c\/h2\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat are the signs of a worn alternator belt?\u003c\/summary\u003e\n  \u003cp\u003eCommon signs include squealing during startup or acceleration, visible cracking, fraying, glazing, belt dust, unusual vibration, or reduced alternator-charging performance. Inspect the pulleys as well as the belt when diagnosing a problem.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eHow should the belt be tensioned?\u003c\/summary\u003e\n  \u003cp\u003eUse the tension procedure and deflection specification for your exact engine model. Excessive tension can damage bearings, while insufficient tension can cause slipping and poor charging.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWill this belt fit my Yanmar engine?\u003c\/summary\u003e\n  \u003cp\u003eThis listing is for Yanmar 2GM20F and 3GM30F engines with fresh-water closed cooling. Confirm the full model designation, cooling configuration, and one of the listed OEM reference numbers before ordering.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eDoes this listing include an alternator or installation hardware?\u003c\/summary\u003e\n  \u003cp\u003eNo. This listing includes one replacement alternator belt only. The alternator, fasteners, pulleys, and other engine components are not included.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhen should the belt be replaced?\u003c\/summary\u003e\n  \u003cp\u003eInspect the belt during routine engine maintenance and replace it when cracking, fraying, glazing, contamination, abnormal noise, or other significant wear is present. Follow the engine manufacturer’s maintenance recommendations where available.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003ch2\u003eSafety \u0026amp; Important Information\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eVerify the engine model, cooling configuration, belt routing, and OEM reference number before purchase.\u003c\/li\u003e\n  \u003cli\u003eDo not work on a running engine. Disconnect the battery and allow hot components to cool before installation.\u003c\/li\u003e\n  \u003cli\u003eUse the engine manufacturer’s service procedure for belt tension and fastener torque.\u003c\/li\u003e\n  \u003cli\u003eThis is an aftermarket replacement belt, not a Yanmar-branded OEM component.\u003c\/li\u003e\n  \u003cli\u003eProfessional installation is recommended if the correct belt routing or tension specification is uncertain.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eAbout Sea Sierra\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMarine Parts Focus\u003c\/strong\u003e — Replacement components selected for marine engine service applications.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eApplication Guidance\u003c\/strong\u003e — Check the complete model and cooling-system details before ordering.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eReplacement Value\u003c\/strong\u003e — Practical aftermarket parts for routine maintenance and repair.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/section\u003e","brand":"SeaSierra","offers":[{"title":"Default Title","offer_id":50723797860667,"sku":"23BL240","price":18.7,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/23BL240_2.jpg?v=1763032037"}],"url":"https:\/\/seasierra.com\/collections\/yanmar-4-stroke-20-27hp-marine-engine-parts.oembed","provider":"SeaSierra","version":"1.0","type":"link"}