Updated October 26, 2026
How surveys describe it
Wording varies by surveyor. Illustrative examples (not quoted from any real survey):
- “Exhaust risers show external corrosion and scale; recommend replacement.”
- “Riser joints weeping at the manifold.”
What it is
On gas inboards and sterndrives, cooling water is mixed into the exhaust through cast-iron manifolds, risers and elbows. They corrode from the inside, especially in salt water, and are treated as wear items.
How serious it is
Worn risers can let water back into the engine, which can damage it badly. Owners in salt water describe them as semi-disposable; one owner reported a set lasting eight seasons.[1]
In our reports this usually lands under Negotiate. Your survey's details decide.
What it typically costs
| Scope | Estimated range |
|---|---|
| 1 engine | $1,500–$3,000 |
| 2 engines | $3,000–$6,000 |
These are whole-job ranges drawn from published figures.[1]
- Gas V8 inboard or sterndrive
- Shop installs aftermarket or OEM cast parts
- Seized bolts and access raise labor
Estimates to help you frame a conversation with a yard, not quotes. Real prices depend on the boat, the yard, access and what's found once work starts. Confirm with your surveyor or a qualified yard.
What to ask your surveyor or yard
- Is there any sign of water in the oil or cylinders?
- When were the risers last replaced, and are there receipts?
- Does the corrosion look external only, or are joints leaking?
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- MerCruiser exhaust manifold set, iboats forums (owner reports). Boat owners' reported prices. Accessed 2026-10-26.