The Volvo Penta D2 is a common diesel in sailing yachts and small motorboats. Its documented weak point is where the exhaust elbow, the bend where seawater is injected into the exhaust, bolts to the aluminium heat exchanger. Corrosion there can block the water, overheat the engine and leak exhaust gas into the boat.
The elbow and heat exchanger joint
What happens. In Mark Ryan's repair for Practical Boat Owner on a D2-55A, the face of the aluminium heat exchanger had corroded away where the elbow bolts on, and exhaust gas was leaking into the cabin. He puts it down to galvanic corrosion: a steel elbow, a stainless gasket and an aluminium heat exchanger together in a wet joint.
The cost of leaving it. Volvo advised him to replace the whole heat exchanger, at over £3,000 (about $3,900 or €3,500, converted). He had the face welded and machined instead, fitted a stainless elbow with a composite gasket, coated the studs against corrosion and pressure tested each chamber.
How long an elbow lasts. He reports Volvo telling him that elbows should only last a maximum of 10 years.
Where to look. The flange where the elbow meets the heat exchanger: white salt crystals, rust weeping, soot or exhaust staining. Smell for exhaust in the cabin with the engine running. Ask when the elbow was last replaced, and whether it's the original steel part or a stainless one.
Overheating and exhaust in the boat
A corroded or blocked elbow restricts the cooling water leaving the engine. Watch the temperature on the sea trial and check water flow at the exhaust outlet. Any exhaust leak inside the boat makes a working CO alarm essential; see no CO alarm. For recalls and other Volvo Penta engines, see the Volvo Penta page.
What to check on a Volvo Penta D2
| Area | What to look for | Source of the concern |
|---|---|---|
| Elbow to heat exchanger joint | Salt crystals, weeping, soot, corrosion of the aluminium face | PBO |
| Elbow age and material | Original steel or replaced stainless; date of replacement | PBO, reporting Volvo |
| Cabin | Exhaust smell with the engine running; CO alarm fitted and working | PBO |
| Cooling | Temperature on the sea trial, water flow at the outlet | PBO |
Writing it up
"Engine, Volvo Penta D2-55: salt deposits and rust weeping at the exhaust elbow to heat exchanger flange. Elbow appears original, no record of replacement. Recommend the elbow is removed and the heat exchanger face inspected for corrosion before the vessel is used, and a CO alarm fitted in the accommodation." Note the engine serial number and hours in the particulars.