Product Description
Sierra 18-1903 marine port exhaust manifold for OMC Cobra V8 5.0L and 5.7L (305 and 350 cu in) V8 marine gas engines. GM/Chevrolet small block. Fits many OMC 1989 and earlier models with log style (end rise) manifolds. Comes with gasket set. Each "Buy It Now" is for one port-side manifold. Find the starboard side here.
Riser mating bolt dimensions are 3-7/8" (98.4mm) by 2-19/32" (65.9mm) bolt center-to-center.
This manifold is new, high-quality cast iron construction, and is made in the USA. For tips on replacing exhaust manifolds and risers, see my eBay guide. To determine if this is the correct replacement for you, look on your current manifold for casting numbers and match them to the cross-reference below:
Sierra Catalog
View the Sierra online catalog for part numbers, descriptions, and application fitment on over 6,000 marine parts. If you have an OEM or aftermarket part number you're trying to replace, you can use the Sierra SONAR part number lookup to find the correct Sierra part for your application.
Search all of my other Sierra items here.
Tech Support
If the part numbers and information above aren't enough to determine fitment, you can contact Sierra's Tech Support Line directly via email or phone.
Warranty
Sierra products are engineered to meet or exceed OEM standards, and stand up in harsh marine environments. Every new Sierra part comes with a limited lifetime warranty that covers the useful life of the product against any defects in workmanship and materials. The warranty does not cover normal wear and tear.
Riser mating bolt dimensions are 3-7/8" (98.4mm) by 2-19/32" (65.9mm) bolt center-to-center.
This manifold is new, high-quality cast iron construction, and is made in the USA. For tips on replacing exhaust manifolds and risers, see my eBay guide. To determine if this is the correct replacement for you, look on your current manifold for casting numbers and match them to the cross-reference below:
| Cross Reference | Part Number |
|---|---|
| OMC | 912442, 909279, 910144 |
| Osco Motors | 2442 |
| Barr Marine | OMC-1-912442 |
| Sierra Marine | 18-1903 |
| Aqua Power | 5513 |
| GLM Products | 51420 |
Sierra Catalog
View the Sierra online catalog for part numbers, descriptions, and application fitment on over 6,000 marine parts. If you have an OEM or aftermarket part number you're trying to replace, you can use the Sierra SONAR part number lookup to find the correct Sierra part for your application.
Search all of my other Sierra items here.
Tech Support
If the part numbers and information above aren't enough to determine fitment, you can contact Sierra's Tech Support Line directly via email or phone.
Warranty
Sierra products are engineered to meet or exceed OEM standards, and stand up in harsh marine environments. Every new Sierra part comes with a limited lifetime warranty that covers the useful life of the product against any defects in workmanship and materials. The warranty does not cover normal wear and tear.
Payment
- PayPal is the preferred method to make secure payments with a credit/debit card or bank account.
- Sales tax is charged for Washington state USA addresses. Other states are not charged tax. International locations may have import duty/tax (please contact your customs department).
Shipping and Tracking
- Items ship same day if purchased on a business day before 1pm for UPS or 10am for USPS (Pacific Time).
- Tracking info is emailed once an item ships, and is also available in your Purchase History on eBay. Double-check that your email address is correct and confirmations aren't going into spam/junk folders.
- Faster shipping options are available in the Shipping and Payments section.
- Business days are Monday through Friday, not including holidays.
- Pickup is not available. All items must be shipped.
International Buyers
- Items heading outside the USA cannot be used for military or government applications. The seller and marketplace expressly disclaim liability for misuse of its products.
- Shipping prices shown do not include import taxes or customs duties. Contact your country's customs department for more information.
- Items cannot be marked as gift or have a lowered value on the documentation. It is unlawful to forge international documents.
- Most international shipments ship via DHL Express or USPS Express Mail.
Warranty and Returns
This item has a Limited lifetime warranty covering any manufacturer defects. Defective items are generally replaced within a few business days, plus time in transit, and there will never be any extra cost to you.
Lost Items, Damage, or Other Problems
If your item has a problem, such as being delayed, lost, or damaged by the shipping company, or if there are missing components, please send an eBay Message or Email right away describing the nature of the problem and its urgency (include pictures if possible). Everything will be done to assist you in a timely manner and there will never be any additional cost to you.
Regular Returns
You may return an item if you no longer need it or don't want it anymore. Returns are accepted on items still in the same condition they arrived in. There may be a 10% restocking fee and all shipping costs must be covered by the buyer. To initiate a return, log in to eBay, go to your "Purchase History", and use the "Return" link next to the transaction.
Lost Items, Damage, or Other Problems
If your item has a problem, such as being delayed, lost, or damaged by the shipping company, or if there are missing components, please send an eBay Message or Email right away describing the nature of the problem and its urgency (include pictures if possible). Everything will be done to assist you in a timely manner and there will never be any additional cost to you.
Regular Returns
You may return an item if you no longer need it or don't want it anymore. Returns are accepted on items still in the same condition they arrived in. There may be a 10% restocking fee and all shipping costs must be covered by the buyer. To initiate a return, log in to eBay, go to your "Purchase History", and use the "Return" link next to the transaction.
Frequently Asked Questions
Q: Does this fit the port or starboard side of the engine?
This manifold fits the port side of the engine.
Q: What should I torque the bolts to?
It depends on the grade of bolt and thread size. Use the below chart to determine the torque rating you should use:
Q: How does the quality compare to other brands?
This manifold will meet or exceed the quality of the original factory manifold. It is manufactured in the USA and comes with high-quality, thick gaskets (not thin paper).
Q: Who manufactures this item?
This item is manufactured by Sierra.
Q. What are the shipping dimensions and weight?
This item ships in a box approximately 20" x 10" x 6" and weighs approximately 37 lbs.
This manifold fits the port side of the engine.
Q: What should I torque the bolts to?
It depends on the grade of bolt and thread size. Use the below chart to determine the torque rating you should use:
Q: How does the quality compare to other brands?
This manifold will meet or exceed the quality of the original factory manifold. It is manufactured in the USA and comes with high-quality, thick gaskets (not thin paper).
Q: Who manufactures this item?
This item is manufactured by Sierra.
Q. What are the shipping dimensions and weight?
This item ships in a box approximately 20" x 10" x 6" and weighs approximately 37 lbs.
Please read the information above thoroughly before asking a question. Questions are answered Mon-Fri 8am-4pm PST. All coorespondance must be via Email or eBay Message.
Thank you for your time!
Thank you for your time!