The top picks are 350 GPH or similar capacity water pumps that fit common GM V6/V8 marine engines and MerCruiser, Volvo Penta, and other stern-drive systems. This guide helps buyers choose pumps that deliver reliable cooling and circulation while avoiding compatibility issues. Best for: boat owners needing reliable, OEM-like replacements; DIY installers seeking straightforward fitment; and users upgrading from older pumps where corrosion resistance matters.
Summary of selected products
- Tykick Circulating Water Pump Assembly — Broad GM/MerCruiser compatibility; best for owners with early GM small-block engines.
- HeuroFosh 3853850 Sea Water Pump — Bi-directional design; better for mixed steel/composite timing covers.
- EvTok Sea Water Pump Kit — Wide OEM cross-reference; good all-around replacement for 1968-1998 era engines.
- UANOFCN Sea Water Pump — OEM-number compatibility; durable copper impeller and stainless back cover.
- SEAFLO 01 Series 350 GPH Bilge Pump — Practical for bilge and livewell applications; best value for 350 GPH needs.
Tykick Circulating Water Pump Assembly
This circulating water pump assembly is designed for MerCruiser, Volvo Penta, OMC, and GM small-block engines (V6 262 cu in and V8 305, 350, 377 cu in). It fits GM 4.3L V6 engines up to 2007 and is compatible with 5.0L, 5.7L, and some 6.2L small-block V8s. Best for: engine owners needing a broad-fit, cross-reference pump. Choose this if your model matches the listed GM/V6/V8 ranges. Caution: verify specific model numbers and dimensions to ensure fitment before purchase.
HeuroFosh 3853850 Sea Water Pump
Bi-directional design fits steel and composite timing chain covers on small-block V8 engines. Replaces multiple MerCruiser, MerCruiser 46-8M0113734, 8503991, 17477, and related part numbers. Best for: users replacing OEM pumps across MerCruiser/GM V6/V8 ranges; provides broad cross-compatibility. Caution: confirm timing cover material and engine family to ensure bi-directional compatibility.
EvTok Sea Water Pump Kit
Widely cross-referenced to fit Volvo Penta, MerCruiser, OMC stern drives, and Indmar/Chrysler GM V6 and V8 engines from 3.8L to 5.7L. Replaces 8M0113734, 8503991, 17437, and many related part numbers. Best for: a versatile replacement kit for multiple brands in older0400- era engines. Caution: assess the exact engine displacement and production year to ensure compatibility.
UANOFCN Sea Water Pump
OEM part number compatibility includes 8M0113734, 15201, 17437, 20318, 35341, 37951, 52226, 54793, 60658, 382218, 811841, 850399, 878341, 980477, 985429, 3853850, 7142520, 8503991, and 18-3599-2, among others. Durable construction features a stainless steel back cover and copper impeller for corrosion resistance. Best for: buyers needing wide OEM cross-references and robust materials. Caution: 2007 and earlier GM 4.3L V6 engines are specified; confirm engine year and model before purchase.
SEAFLO 01 Series 350 GPH Bilge Pump
12V bilge pump with 350 GPH flow, 3/4″ outlet, anti-airlock protection, and a four-year warranty. Best for: bilge or livewell applications where compact, reliable flow is needed. Caution: designed primarily for bilge use; verify compatibility with non-bilge marine fittings and mounting, if used elsewhere.
Buying Guide
Key factors to consider when choosing a marine 350 water pump:
- Engine compatibility: Match the pump’s OEM part numbers, displacement, and year range to your GM V6/V8 or MerCruiser engine.
- Material quality: Copper impellers and stainless steel back covers improve corrosion resistance in saltwater environments.
- Flow needs: 350 GPH is common for bilge or cooling tasks; evaluate your boat size, engine cooling demand, and auxiliary systems.
- Bi-directional capability: Some pumps support different timing cover configurations; verify this with your engine layout.
- Cross-reference coverage: Pumps listing many OEM numbers offer flexibility if your engine was produced under multiple part numbers.
- Installation considerations: Check fitting sizes, outlet diameters, and compatibility with timing chain cover materials.
Frequently Asked Questions
- What does 350 GPH mean for marine pumps?
It refers to the maximum flow rate in gallons per hour. Higher GPH can move more water for cooling or bilge duties, but ensure compatibility with your system’s fittings and head height.
- Can I use a 350 GPH pump for both cooling and bilge needs?
Yes, many 350 GPH pumps are suitable for both cooling circuits and bilge applications, but check the pump’s intended use and certifications.
- Why is OEM cross-reference important?
OEM cross-reference ensures the pump fits your engine across model years. It helps avoid misfits and ensures proper pump rotation and mounting.
- What maintenance improves pump longevity?
Regular inspection for impeller wear, seals, and mounting integrity; keep corrosion in saltwater environments in mind and replace as needed.
- Is bi-directional important for marine pumps?
Bi-directional pumps tolerate different timing cover orientations. Confirm your engine’s cover type before purchasing a bi-directional pump.
- When should I choose a SEAFLO bilge pump over a dedicated cooling pump?
Use SEAFLO 350 GPH for bilge or livewell tasks where a compact, reliable pump is sufficient; use dedicated cooling pumps for engine cooling circuits requiring higher stability and compatibility with cooling hoses.