Which engine was standard in the Hallberg-Rassy 31, and what weaknesses should I check?
I'm looking at a Hallberg-Rassy 31 with a Volvo Penta diesel and saildrive. Which engine should it have originally, and what expensive problems should I check before buying?
Answer
The Hallberg-Rassy 31 used Volvo Penta diesels: older boats commonly have the MD2020, while the later Mk II specification lists the three-cylinder, freshwater-cooled D1-20 producing 14 kW/19 hp. Check the engine identification plate and maintenance invoices first, as installations vary by build year and some boats have been re-engined; focus the inspection on cooling, the exhaust mixing elbow and the saildrive.
Identify the engine and drive
The later HR 31 Mk II paired the D1-20 with a saildrive and a two-bladed bronze folding propeller. Its published specification also lists a 115 A alternator, a 60-litre stainless steel diesel tank and separate 62 Ah starting and domestic batteries, though owners often upgrade the batteries.
Earlier HR 31s commonly carry the roughly 19 hp MD2020; the earliest examples can have its predecessor, the Volvo Penta 2002, a two-cylinder engine of about 18 hp. Confirm the boat's equipment rather than identifying its engine solely by the advertised year. The HR 310 is a separate model: its Yanmar 3YM20C/SD20 specification does not apply to the HR 31.
Record the engine model, serial number and saildrive identification separately before ordering parts. A replacement engine may retain an older drive, so an invoice for a new engine does not establish the age of the whole installation.
Check cooling and exhaust
These engines can give long service, but seawater components deteriorate even with low engine hours. Freshwater cooling means coolant circulates through the engine; seawater still passes through the heat exchanger and exhaust system.
- Exhaust mixing elbow: inspect for rust, salt tracks, leakage and internal restriction. Carbon and corrosion can narrow the water-injection passages, causing overheating or poor performance under load. An external inspection cannot establish the elbow's internal condition.
- Raw-water pump: look for drips around the shaft and salt deposits beneath it. Ask when the impeller was changed and whether any missing blades were recovered from the downstream cooling circuit.
- Heat exchanger: check end caps and hose connections, and look for evidence of coolant loss. Ask about cleaning and coolant replacement, particularly if the boat has a history of overheating.
- Exhaust hose and waterlock: look for cracking, leakage and heat damage. Check that any fitted anti-siphon valve has been serviced.
Close the seawater inlet before opening the pump or strainer, and reopen it before starting. Investigate persistent overheating under load; a strong exhaust discharge at idle does not prove the cooling system is healthy.