{"product_id":"sierra-18-99525-lower-unit-adapter-kit-gear-case","title":"Sierra 18-99525 Lower Unit Adapter Kit | Gear Case","description":"\u003cp class=\"nvn-hero\"\u003eThe Sierra 18-99525 Lower Unit Adapter Kit lets a CDI Electronics gear case pressure and vacuum tester thread into more engines. It packs metric, Suzuki, and Volvo adapters plus threaded and unthreaded nozzles, so you can pressure and vacuum test outboard and sterndrive seals before a leak ruins the gears.\u003c\/p\u003e\n\n\u003cdiv class=\"nvn-description\"\u003e\n\u003cp\u003eThe Sierra 18-99525 Lower Unit Adapter Kit is the set of fittings you reach for when you're pressure and vacuum testing a gear case and the tester in your hand won't thread cleanly into the drain or vent hole in front of you. Different outboards and sterndrives use different port threads, and this kit bridges that gap. It's built to work with the CDI Electronics gear case pressure and vacuum tester system, so one tester and hose setup carries across Suzuki, Volvo, and metric-threaded lower units without hunting down a one-off fitting every time.\u003c\/p\u003e\n\u003cp\u003eHere's what's actually in the box. You get the 551-334M metric adapter, the 551-334S Suzuki adapter, the 551-334V Volvo adapter, and the 551-33TN threaded and unthreaded nozzles. That's it, and that's the point. This is the adapter kit, not the tester. The 551-34PV pressure and vacuum tester, the 551-33-1 gear case filler, and the 551-34HA and 551-34HB hoses are separate pieces. If you already run that CDI tester setup on your bench, this kit is the missing link that lets it fit more engines.\u003c\/p\u003e\n\u003cp\u003eWhy bother pressure testing at all? Because a gear case lives on three seals, the driveshaft seal up top, the prop shaft seal at the back, and the shift shaft seal. Any one of them can let water sneak in and gear oil weep out, and by the time you spot milky lube on the drain plug the damage is often already done. A pressure and vacuum check catches a weak seal before it turns into a spun bearing or a chewed-up gearset. You pressurize the housing and watch the gauge hold, then pull a vacuum and watch it hold again. Steady needle, good seals. Dropping needle, time to pull it apart.\u003c\/p\u003e\n\u003cp\u003eThe adapters matter more than they look. A Suzuki lower unit doesn't share the same fill and vent thread as a Volvo Penta leg, and plenty of newer cases run metric threads that a standard nozzle just won't bite. Thread the wrong fitting in and you either can't build pressure or you cross-thread a soft aluminum port, which is a bad afternoon. Match the adapter to the engine and the tester seals up on the first try.\u003c\/p\u003e\n\u003cp\u003eA few notes from the field. Go easy on torque with the Suzuki adapter, especially on the bigger DF-series outboards, since those threads will strip if you really lean on them. On older Volvo SP and 290 legs, an extra O-ring on the adapter helps it hold vacuum when the port is worn. And if you're chasing a phantom leak on an engine running thick gear lube, warm the unit up or switch to the recommended synthetic before you test, because cold heavy oil can mask a slow weep and read like a false pass. The threaded nozzle handles ports with clean threads, and the unthreaded nozzle covers the rest.\u003c\/p\u003e\n\u003cp\u003eThere's a rhythm to a full lower-unit service, and this kit fits right into it. Drain the old gear oil, refill from the bottom with the CDI filler so you push the air out the top, then cap it and run the pressure and vacuum test to confirm the fresh fill isn't going anywhere. On a saltwater boat that gets used hard, doing this once a season is cheap insurance. Hoses do wear, so if a line ever develops a pinhole after a few years of checks, swap the hose and keep the adapters. They'll outlast several hoses.\u003c\/p\u003e\n\u003cp\u003eWho's this for? Marine techs and serious owners who service their own lower units every season. If you're already changing your own gear oil with the CDI filler, adding this adapter kit turns a fluid change into a full seal inspection. It's the same reason shops keep it on the bench. One tester, one set of adapters, and you can properly test almost anything that rolls through the door. Sierra builds this kit to meet or beat the original tooling it replaces, the same standard behind the thousands of engine parts they supply to builders and boatyards. It isn't glamorous gear. But it's the difference between guessing a gear case is dry and knowing it.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul class=\"nvn-features\"\u003e\n  \u003cli\u003eIncludes the 551-334M metric adapter for gear cases with metric fill and vent threads\u003c\/li\u003e\n  \u003cli\u003eIncludes the 551-334S Suzuki adapter, sized for Suzuki outboard lower units\u003c\/li\u003e\n  \u003cli\u003eIncludes the 551-334V Volvo adapter for Volvo Penta sterndrive legs\u003c\/li\u003e\n  \u003cli\u003eIncludes the 551-33TN threaded and unthreaded nozzles to match clean or worn port threads\u003c\/li\u003e\n  \u003cli\u003eWorks with the CDI Electronics 551-34PV pressure and vacuum tester, so one tester covers more engines\u003c\/li\u003e\n  \u003cli\u003ePairs with the 551-33-1 gear case filler for a complete drain, fill, and seal-test service\u003c\/li\u003e\n  \u003cli\u003eAdapter kit only, the tester, filler, and hoses are sold separately\u003c\/li\u003e\n  \u003cli\u003eSierra-engineered to meet or exceed the original tooling it replaces\u003c\/li\u003e\n  \u003cli\u003eLets you test the driveshaft, prop shaft, and shift shaft seals before water damage sets in\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's included in the Sierra 18-99525 adapter kit?\u003c\/summary\u003e\n    \u003cp\u003eYou get four pieces: the 551-334M metric adapter, the 551-334S Suzuki adapter, the 551-334V Volvo adapter, and the 551-33TN threaded and unthreaded nozzles. The tester, filler, and hoses are not included.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eDoes this kit include the pressure and vacuum tester?\u003c\/summary\u003e\n    \u003cp\u003eNo. This is the adapter kit only. It's designed to work with the CDI Electronics 551-34PV pressure and vacuum tester and the 551-33-1 gear case filler, which are sold separately.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat engines do the adapters fit?\u003c\/summary\u003e\n    \u003cp\u003eThe kit covers Suzuki outboards, Volvo Penta sterndrive legs, and metric-threaded gear cases. Match the right adapter to the engine's fill and vent port and the tester threads in cleanly.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat is gear case pressure and vacuum testing for?\u003c\/summary\u003e\n    \u003cp\u003eIt checks the driveshaft, prop shaft, and shift shaft seals for leaks. Catching a weak seal early keeps water out of the gear oil before it ruins the bearings and gears.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWill the Suzuki adapter fit larger Suzuki outboards?\u003c\/summary\u003e\n    \u003cp\u003eYes, it's made for Suzuki lower units. Just go easy on torque, especially on the bigger DF-series, because the threads can strip if you overtighten them.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eMy Volvo leg won't hold vacuum. What should I check?\u003c\/summary\u003e\n    \u003cp\u003eOn older Volvo SP and 290 legs the port can be worn. Adding an extra O-ring on the adapter usually helps it seal and hold vacuum.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eCan I use this with the CDI gear case filler?\u003c\/summary\u003e\n    \u003cp\u003eYes. It pairs with the 551-33-1 filler so you can drain, refill from the bottom, and then pressure and vacuum test the unit in one service.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eThe gauge shows a slow leak but I'm not sure it's real. What now?\u003c\/summary\u003e\n    \u003cp\u003eThick cold gear oil can mask a slow weep and read like a false pass, or hide a real one. Warm the unit or use the recommended synthetic lube and test again to confirm.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eIs this a genuine CDI kit?\u003c\/summary\u003e\n    \u003cp\u003eIt's a Sierra Marine kit engineered to work with the CDI Electronics tester system and to meet or exceed the original tooling it replaces.\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 18-99525 Lower Unit Adapter Kit\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\u003e18-99525\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eUPC\u003c\/th\u003e\n\u003ctd\u003e808282394882\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eProduct Type\u003c\/th\u003e\n\u003ctd\u003eLower Unit Adapter Kit\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eApplication\u003c\/th\u003e\n\u003ctd\u003eGear case pressure and vacuum testing\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eCompatible Tester\u003c\/th\u003e\n\u003ctd\u003eCDI Electronics 551-34PV Pressure and Vacuum Tester\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eCompatible Gear Case Filler\u003c\/th\u003e\n\u003ctd\u003eCDI Electronics 551-33-1\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eCompatible Hose Assemblies\u003c\/th\u003e\n\u003ctd\u003e551-34HA, 551-34HB\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eIncluded Metric Adapter\u003c\/th\u003e\n\u003ctd\u003e551-334M\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eIncluded Suzuki Adapter\u003c\/th\u003e\n\u003ctd\u003e551-334S\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eIncluded Volvo Adapter\u003c\/th\u003e\n\u003ctd\u003e551-334V\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eIncluded Nozzles\u003c\/th\u003e\n\u003ctd\u003e551-33TN Threaded and Unthreaded Nozzle\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eEngine Applications\u003c\/th\u003e\n\u003ctd\u003eSuzuki outboards, Volvo Penta sterndrives, metric-thread gear cases\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eInterchange\u003c\/th\u003e\n\u003ctd\u003eCDI Electronics 551-334K\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's included in the Sierra 18-99525 adapter kit?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"You get four pieces: the 551-334M metric adapter, the 551-334S Suzuki adapter, the 551-334V Volvo adapter, and the 551-33TN threaded and unthreaded nozzles. The tester, filler, and hoses are not included.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Does this kit include the pressure and vacuum tester?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"No. This is the adapter kit only. It's designed to work with the CDI Electronics 551-34PV pressure and vacuum tester and the 551-33-1 gear case filler, which are sold separately.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What engines do the adapters fit?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"The kit covers Suzuki outboards, Volvo Penta sterndrive legs, and metric-threaded gear cases. Match the right adapter to the engine's fill and vent port and the tester threads in cleanly.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What is gear case pressure and vacuum testing for?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It checks the driveshaft, prop shaft, and shift shaft seals for leaks. Catching a weak seal early keeps water out of the gear oil before it ruins the bearings and gears.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Will the Suzuki adapter fit larger Suzuki outboards?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Yes, it's made for Suzuki lower units. Just go easy on torque, especially on the bigger DF-series, because the threads can strip if you overtighten them.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"My Volvo leg won't hold vacuum. What should I check?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"On older Volvo SP and 290 legs the port can be worn. Adding an extra O-ring on the adapter usually helps it seal and hold vacuum.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Can I use this with the CDI gear case filler?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Yes. It pairs with the 551-33-1 filler so you can drain, refill from the bottom, and then pressure and vacuum test the unit in one service.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"The gauge shows a slow leak but I'm not sure it's real. What now?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Thick cold gear oil can mask a slow weep and read like a false pass, or hide a real one. Warm the unit or use the recommended synthetic lube and test again to confirm.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Is this a genuine CDI kit?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It's a Sierra Marine kit engineered to work with the CDI Electronics tester system and to meet or exceed the original tooling it replaces.\"\n            }\n        }\n    ]\n}\n\u003c\/script\u003e\n","brand":"Sierra Marine","offers":[{"title":"Default Title","offer_id":45072311550045,"sku":"2009202","price":49.69,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0299\/7266\/0317\/files\/ImageServerAPI_105e3638-72ad-4cb3-9add-c083fb75e97f.jpg?v=1789736860","url":"https:\/\/nvnmarine.com\/products\/sierra-18-99525-lower-unit-adapter-kit-gear-case","provider":"NVN Marine","version":"1.0","type":"link"}