Barr MerCruiser GM 7.4L 454 502 Lower Thermostat Housing 29-90736
BAMC29-90736
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Barr MerCruiser Big-Block Lower Housing
GM 7.4L / 454 / 502 | Design No. 1
Barr Marine aftermarket lower thermostat housing for legacy MerCruiser GM/Chevrolet big-block centre-riser cooling systems. It replaces the Design No. 1 lower housing used on specified 330, 340 and 454 Magnum applications.
Key Features
- Lower thermostat housing only
- For GM/Chevrolet big-block marine engines
- Design No. 1 centre-riser cooling system
- Barr Marine aftermarket casting
- Replaces MerCruiser 90736 assembly family
Technical Specs
| Part type | Lower thermostat housing |
| Engine | GM big-block V8 |
| Displacement | 7.4L / 454 / 502 cu in |
| Housing design | MerCruiser Design No. 1 |
| SKU | BAMC29-90736 |
Compatibility / Fitment Guide
| Application | Verified fitment | Notes / exclusions |
|---|---|---|
| MerCruiser 330 / 340 Inboard | Legacy big-block Chevrolet centre-riser installations | Confirm original lower housing reference. |
| MerCruiser 454 Magnum | Applicable inboard/sterndrive units using Design No. 1 housing | Inspect hose ports and upper-cover interface. |
| GM 502 applications | Only conversions/engines retaining this Design No. 1 centre-riser housing | Do not select from displacement alone. |
| Exclusion | Small-block V8 and later thermostat housing designs | Port layout and cover differ. |
Match the complete model, serial number, housing design and original part reference.
OEM Cross Reference
| Barr Marine | MC-29-90736 |
| MerCruiser | 90736A4; 90736A18; 90736A23 application family |
| OSCO | MC552-BB |
| Upper cover used with housing | MC-29-47442 |
| 4Boats SKU | BAMC29-90736 |
This is an aftermarket replacement. Manufacturer references are provided for identification only.
Questions & Answers
Is the thermostat included?
No. This listing is for the lower housing.
Does it fit every 7.4L MerCruiser?
No. It must use the legacy Design No. 1 centre-riser housing.
What upper cover matches?
Barr identifies MC-29-47442 for this lower housing.
Installation note: Inspect corrosion and sealing faces, use the specified gasket/seal, and verify leak-free operation after installation.
For the products under £150 the shipping is £6.99.
Free delivery for most items over £150.
