Which engine was fitted to a Malö 36, and what common problems should I check?

Most Malö 36s were fitted with a naturally aspirated Yanmar 3JH-series three-cylinder diesel of roughly 38 to 40 hp, usually driving a conventional propeller shaft. Check the engine identification plate first: the exact model varies with build year and replacement history, and cooling-system condition matters more than engine hours alone.

Identify the engine and gearbox

The usual engines are the earlier 3JH2E, commonly quoted at about 38 hp, the 3JH3E at about 40 hp, and the later 3JH4E, often advertised as 39 or 40 hp. Published horsepower figures vary slightly with the rating convention. A sales description saying "Yanmar 40" does not adequately identify the engine.

Photograph the engine model and serial plate, plus the separate gearbox plate. Compare them with service invoices and any replacement-engine paperwork. Use those details when buying filters, impellers, belts and exhaust parts, rather than relying on the boat's year.

Ask for records of coolant changes, valve-clearance checks, injector work and heat-exchanger servicing. These engines have mechanical fuel injection, so a sound example should be straightforward to maintain. There is no fixed age or hours limit at which replacement makes sense.

Check cooling and exhaust

Check early for restricted seawater flow and a deteriorating exhaust mixing elbow. Both can cause overheating, loss of power and expensive secondary damage, even if the engine starts readily.

With the engine cold, inspect the following:

• Seacock, strainer and suction hose: look for leaks, cracked hose, loose clips and an obstructed strainer. A suction-side air leak may reduce cooling without leaving a puddle.
• Raw-water pump: check for salt deposits or leakage around the shaft and cover. Establish when the impeller was changed. If blades were missing, ask whether the fragments were recovered downstream.
• Heat exchanger: look for staining around end caps, neglected coolant and evidence of repeated topping up. A clear strainer does not mean the exchanger tubes are clear.
• Mixing elbow and exhaust hose: check for rust, salt tracks, cracking and heat damage. Internal carbon or corrosion can restrict the elbow even when its exterior looks sound.

Watch the exhaust-water discharge immediately after starting, then monitor temperature under sustained load. Water at the outlet alone does not prove adequate cooling. Close the seawater seacock before dismantling the cooling circuit and reopen it before starting. Never remove a hot coolant cap.

Cold start and sea trial

Arrange for the engine to be cold when you arrive. Check the oil and coolant first. An unexpectedly high oil level, milky oil or oily coolant needs investigation, although clean-looking fluids cannot establish internal condition.