{"product_id":"sierra-18-99161-cdm-module-mercury-force-outboards","title":"Sierra 18-99161 CDM Module | Mercury \u0026 Force Outboards","description":"\u003cp class=\"nvn-hero\"\u003eThe Sierra 18-99161 is a direct-replacement CDM ignition module for a huge range of Mercury and Force outboards. If a cylinder's gone dead, your idle's turned rough, or the engine won't fire, a failed CDM is one of the first things we check. This one drops right in and gets your spark back.\u003c\/p\u003e\n\n\u003cdiv class=\"nvn-description\"\u003e\n\u003cp\u003eThe Sierra 18-99161 is a CDM, short for Capacitor Discharge Module. On these outboards, the CDM is the heart of the ignition. It packs the ignition coil, the electronics that store and dump the charge, and the driver that fires the plug into one sealed unit. When it's working, you don't think about it. When it fails, you feel it right away.\u003c\/p\u003e\n\u003cp\u003eSo how do you know a CDM has gone bad? The classic signs are a dead cylinder that won't fire, a rough or lumpy idle, hard starting, or a miss that shows up under load and clears at idle. Sometimes an engine runs fine cold and then starts dropping a cylinder once everything heats up. We've chased plenty of these down on the water, and more often than not a failed module is the culprit once you've ruled out the plugs and wires. Because each cylinder or bank runs its own module on a lot of these engines, a single bad CDM only kills the cylinders it feeds. That's why a four-cylinder Force can limp home running on three.\u003c\/p\u003e\n\u003cp\u003eFitment here is wide. This module covers Mercury Marine outboards from 30 to 300 horsepower built between 1996 and 2007, and Force outboards in the 40, 50, 75, 90, and 120 horsepower sizes from 1996 through 1999. That's a big spread of engines, which is exactly why this part number stays busy. Before you order, it's always worth matching the module you're pulling off against the replacement, since a few engines in that range used different ignition setups across the model years.\u003c\/p\u003e\n\u003cp\u003eSierra builds this as a direct replacement for the original equipment module. It meets or exceeds the OEM part it replaces, so you're not giving anything up by going aftermarket here. Sierra supplies parts to plenty of engine builders and boat manufacturers, and their ignition components have a long track record on exactly these blocks. It drops into the factory location and connects to the factory harness. No splicing, no adapters, no fabrication.\u003c\/p\u003e\n\u003cp\u003eA quick word on diagnosis before you spend money. A CDM either fires or it doesn't, and they tend to fail outright rather than drift. If you've got a spark tester, check for spark on the dead cylinder while the engine cranks. No spark on one cylinder while the others fire is the tell. It's also smart to rule out the cheap stuff first. Fouled plugs, cracked plug wires, a loose ground, or a tired stator feeding weak voltage to the modules can all mimic a bad CDM. Swap-testing a suspect module against a known-good one from another cylinder is the old mechanic's trick. If the dead cylinder follows the module, you've found your problem.\u003c\/p\u003e\n\u003cp\u003eInstall is straightforward for anyone comfortable working around the powerhead. Disconnect the battery first. Note where each lead lands before you unplug anything, and snap a photo if you're not sure. Pull the old module, transfer the leads to the new one connection for connection, and torque the mounting hardware back down. Give the connections a shot of dielectric grease to keep corrosion out. That's the part that kills these modules early, water and corrosion working into the connector over the years.\u003c\/p\u003e\n\u003cp\u003eOne honest bit of advice. If your engine runs several CDMs and one has already failed from age, the others are the same age and living in the same salt air. A lot of owners replace the whole set at once so they're not back in the bilge next month chasing the next one. That's your call and your budget, but it's worth thinking about on an older motor.\u003c\/p\u003e\n\u003cp\u003eThese older two-strokes are simple, torquey, and cheap to keep running when you feed them the right parts. That's a big reason they're still hanging off transoms twenty-plus years later. The ignition is usually the weak link as they age, and a fresh module can make a tired-feeling motor wake right back up. Get the spark clean and consistent across every cylinder, and everything else, throttle response, idle, top-end, tends to fall back into place.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul class=\"nvn-features\"\u003e\n  \u003cli\u003eCapacitor Discharge Module integrates the ignition coil, capacitor, and firing driver in one sealed unit\u003c\/li\u003e\n  \u003cli\u003eFits Mercury Marine outboards 30 to 300 HP, model years 1996 to 2007\u003c\/li\u003e\n  \u003cli\u003eFits Force outboards 40, 50, 75, 90, and 120 HP, model years 1996 to 1999\u003c\/li\u003e\n  \u003cli\u003eDirect OEM replacement, meets or exceeds the original equipment module it replaces\u003c\/li\u003e\n  \u003cli\u003eDrops into the factory location and plugs into the factory harness, no splicing or adapters\u003c\/li\u003e\n  \u003cli\u003eSealed construction stands up to the marine environment for consistent spark season after season\u003c\/li\u003e\n  \u003cli\u003eRestores spark to a dead or misfiring cylinder without a full ignition rebuild\u003c\/li\u003e\n  \u003cli\u003eSierra part number 18-99161, backed by Sierra's OEM-supplier marine parts pedigree\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cdiv class=\"nvn-trust\"\u003e\n  \u003ch2\u003eWhy Buy from NVN Marine\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eAuthorized Sierra Marine reseller, full manufacturer warranty\u003c\/li\u003e\n    \u003cli\u003eNMEA member and ABYC certified, advice from real boat techs\u003c\/li\u003e\n    \u003cli\u003eSame-day shipping before 3 PM ET on in-stock items\u003c\/li\u003e\n    \u003cli\u003eNY headquarters and Fort Lauderdale flagship retail store\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cdiv class=\"nvn-faq\"\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat is a CDM and what does it do?\u003c\/summary\u003e\n    \u003cp\u003eCDM stands for Capacitor Discharge Module. It combines the ignition coil, capacitor, and firing electronics into one sealed unit that delivers spark to the cylinder. On these Mercury and Force outboards it's the core of the ignition system.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow do I know if my CDM has failed?\u003c\/summary\u003e\n    \u003cp\u003eThe usual signs are a dead cylinder, a rough idle, hard starting, or a miss that shows up under load. A spark test on the dead cylinder while cranking confirms it. No spark on one cylinder while the others fire points straight at the module.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWill this fit my engine?\u003c\/summary\u003e\n    \u003cp\u003eIt covers Mercury Marine 30 to 300 HP from 1996 to 2007 and Force 40, 50, 75, 90, and 120 HP from 1996 to 1999. Match the module you're removing against the replacement before install, since a few engines in that range used different ignition setups.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eIs this a direct replacement or do I need to modify anything?\u003c\/summary\u003e\n    \u003cp\u003eIt's a direct OEM replacement. It drops into the factory location and plugs into the factory harness. No splicing, no adapters, no fabrication.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eDo I need to replace all of my modules at once?\u003c\/summary\u003e\n    \u003cp\u003eNot required. A single bad CDM only affects the cylinders it feeds. But on an older motor the other modules are the same age and living in the same salt air, so a lot of owners replace the full set to avoid chasing the next failure.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eCan I install this myself?\u003c\/summary\u003e\n    \u003cp\u003eIf you're comfortable working around the powerhead, yes. Disconnect the battery, note where each lead lands, transfer the connections one at a time, and add dielectric grease to keep corrosion out.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow many CDMs does my engine use?\u003c\/summary\u003e\n    \u003cp\u003eIt varies by engine. Many of these outboards run one module per cylinder or per pair of cylinders. Count the modules on your powerhead before ordering so you know how many you need.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat causes a CDM to fail?\u003c\/summary\u003e\n    \u003cp\u003eAge, heat, and corrosion. Water working into the connector over the years is the big one. A shot of dielectric grease on the connections at install helps the replacement last.\u003c\/p\u003e\n  \u003c\/details\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003ctable class=\"nvn-specs\"\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n\u003cth\u003eTitle\u003c\/th\u003e\n\u003ctd\u003eSierra 18-99161 CDM Ignition Module for Mercury \u0026amp; Force\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eBrand\u003c\/th\u003e\n\u003ctd\u003eSierra Marine\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eManufacturer Part Number\u003c\/th\u003e\n\u003ctd\u003e18-99161\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eUPC\u003c\/th\u003e\n\u003ctd\u003e736983850683\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eProduct Type\u003c\/th\u003e\n\u003ctd\u003eCDM Ignition Module\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eComponent Function\u003c\/th\u003e\n\u003ctd\u003eCapacitor Discharge Module\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eFits Engine Make\u003c\/th\u003e\n\u003ctd\u003eMercury Marine, Force\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eMercury Horsepower Range\u003c\/th\u003e\n\u003ctd\u003e30 to 300 HP\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eMercury Model Years\u003c\/th\u003e\n\u003ctd\u003e1996 to 2007\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eForce Horsepower\u003c\/th\u003e\n\u003ctd\u003e40 \/ 50 \/ 75 \/ 90 \/ 120 HP\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eForce Model Years\u003c\/th\u003e\n\u003ctd\u003e1996 to 1999\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eReplacement Type\u003c\/th\u003e\n\u003ctd\u003eDirect OEM replacement\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eApplication\u003c\/th\u003e\n\u003ctd\u003eOutboard engine ignition\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cscript type=\"application\/ld+json\"\u003e\n{\n    \"@context\": \"https:\/\/schema.org\",\n    \"@type\": \"FAQPage\",\n    \"mainEntity\": [\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What is a CDM and what does it do?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"CDM stands for Capacitor Discharge Module. It combines the ignition coil, capacitor, and firing electronics into one sealed unit that delivers spark to the cylinder. On these Mercury and Force outboards it's the core of the ignition system.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"How do I know if my CDM has failed?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"The usual signs are a dead cylinder, a rough idle, hard starting, or a miss that shows up under load. A spark test on the dead cylinder while cranking confirms it. No spark on one cylinder while the others fire points straight at the module.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Will this fit my engine?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It covers Mercury Marine 30 to 300 HP from 1996 to 2007 and Force 40, 50, 75, 90, and 120 HP from 1996 to 1999. Match the module you're removing against the replacement before install, since a few engines in that range used different ignition setups.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Is this a direct replacement or do I need to modify anything?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It's a direct OEM replacement. It drops into the factory location and plugs into the factory harness. No splicing, no adapters, no fabrication.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Do I need to replace all of my modules at once?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Not required. A single bad CDM only affects the cylinders it feeds. But on an older motor the other modules are the same age and living in the same salt air, so a lot of owners replace the full set to avoid chasing the next failure.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Can I install this myself?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"If you're comfortable working around the powerhead, yes. Disconnect the battery, note where each lead lands, transfer the connections one at a time, and add dielectric grease to keep corrosion out.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"How many CDMs does my engine use?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It varies by engine. Many of these outboards run one module per cylinder or per pair of cylinders. Count the modules on your powerhead before ordering so you know how many you need.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What causes a CDM to fail?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Age, heat, and corrosion. Water working into the connector over the years is the big one. A shot of dielectric grease on the connections at install helps the replacement last.\"\n            }\n        }\n    ]\n}\n\u003c\/script\u003e\n","brand":"Sierra Marine","offers":[{"title":"Default Title","offer_id":45061683511389,"sku":"2008577","price":94.79,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0299\/7266\/0317\/files\/ImageServerAPI_ecfc897b-6d4a-4c21-af30-ae689ddf590e.jpg?v=1789554193","url":"https:\/\/nvnmarine.com\/products\/sierra-18-99161-cdm-module-mercury-force-outboards","provider":"NVN Marine","version":"1.0","type":"link"}