Marine Parts Advisor: Crusader R028021A Big Block Exhaust Manifold

Our goal is to educate you about the purpose and function of many of the popular Crusader marine engine parts required to keep your boat running smoothly. Whether you're a veteran seaman or a novice, one thing you all know is that a boat comes equipped with hundreds of moving parts.

No one person can know everything there is to know about the proper functioning of every boat part. That's why we've tapped the collective wisdom of our long-time technical experts to share their knowledge and expertise.

What You Need to Know About the Crusader Big Block Exhaust Manifold

This Big Block GM center rise exhaust manifold is the original equipment used by Crusader. They began using this manifold in 1992 on the GM 454/7.4L and 502/8.2L engines. Beginning in 2001, it was used with the 496/8.1L GM engine through the end of production in 2012. It had a 20-year run of production when there were a lot of these engines built and is still available for service replacement.

It’s a water-jacket manifold cooled by either the lake water or the engine coolant if it happens to be a fresh-water-cooled, closed-cooled, heat-exchanger-cooled type engine.

The parts of a marine engine exhaust system, e.g. the exhaust elbows, risers, manifolds, are jacketed items. Jacketed means it's basically a casting inside a casting. You have an inner wall and an outer wall; the cooling water is flowing between them, reducing the heat of the casting.

The reason marine exhaust components need to be jacketed and cooled is to reduce the heat inside the engine compartment. There’s just no way you can run dry exhaust components in the bilge of a boat. There’s too much liability; too much heat; too much potential for a fire.

Marine exhaust is not like your car which has metal exhaust components exposed to the air coming in and around it through the engine compartment cooling them. Marine manifolds and exhaust components are enclosed underneath the floor or in the cockpit area generating a tremendous amount of heat which needs to be dissipated.

In raw water applications, the manifold needs to be drained in the winter if you’re in a northern climate. If you’re in a saltwater environment, flushing the engine is the best way to prevent corrosion and extend the life.

There is no routine maintenance. It’s a replacement type component when it fails. The exhaust manifold fails if it becomes cracked, corroded or plugged from scale. Any of these issues can require you to replace the part.

How might someone improperly drain the engine?

You can improperly drain the manifold if you don’t realize the drain is restricted because of sand, silt or corrosion. So, water remains in the manifold, which can freeze, expand and break the manifold. The drain plug hole usually requires probing to make sure there is nothing preventing the water from draining out. You can use a small pick, wire or screwdriver to make sure the drain hole is clear.

Marine Parts Troubleshooters On Call

Once a boat part fails, it's obviously too late to repair it. When possible we've provided tips on simple ways to maintain a part to minimize your cash outlay. We know you'd rather be on the water having fun than on the dock calling your marine mechanic.

That said, if you need help troubleshooting a system failure, give our boat experts a call at 866-388-0390. They'd be happy to steer you in the right direction.