Heating and Cooling› Thermostats, Housings and Fillers

SIERRAMARINE

THERMOSTAT KIT

$47.68

SKU: S08C 18-3668

In Stock
In Stock
Ships by Jun 13
Free Shipping
Non-Returnable Item
INSTALL DIFFICULTY
DIY PRO SHOP

Easy — 1–2 hours

Description

The Sierra 18-3668 is a thermostat kit for Mercruiser Stern Drives. It is designed for engines using 142-degree thermostats and fits 1983 and newer GM V-6 and V-8 engines with standard cooling. The kit includes a thermostat cover gasket, thermostat, and O-ring. It replaces Mallory part number 9-43150 and Mercruiser part numbers 807252T4, 807252Q4, and 807252T7.

Fitment

Fitment Guaranteed

Don’t gamble
on fit.

Log your build in the MOTORMIA app and we’ll guarantee this part fits your exact setup — or your money back, return shipping covered.

Available on iOS & Android

Specifications

BrandSIERRAMARINE
Part NumberS08C 18-3668

Buy with Confidence

Built for enthusiasts. Every order is backed by our 30 day return window on eligible items. Unused and uninstalled products may be returned with approved RMA and no restocking fees when received in new condition. Orders placed through the MOTORMIA app with a complete build qualify for our Fitment Guarantee — free return shipping if the part doesn’t fit your exact setup. The guarantee covers fit only; installation must follow manufacturer instructions, and we recommend a qualified shop for parts marked Difficulty 4–5.

View Full Return Policy