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.
Part Number 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.
Frequently Asked Questions
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.
