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Yanmar 4Lha Dtp8/24/2020
However, a mechanical engine is easier to repair in remote areas.Its the most powerful of a trio of marine diesel engines from 158 to 237bhp that suit semi-displacement cruisers up to 11m as singles, and up to 13m as twins.Sure, electronic engine management reduces exhaust emissions and allows for real-time fuel flow and range-to-empty meters but in remote areas a mechanical engine is easier to repair than an electronic unit.
Yanmar 4Lha Dtp Full Displacement HullsBut these are heavy, achieve maximum output at much lower revs and are intended for full displacement hulls, not semi-displacement cruisers.Yanmar didnt opt for a belt-driven overhead camshaft as with the six and stayed with two valves per cylinder instead of four. Sensibly, the piston stroke isnt much greater than the cylinder bore so piston speeds wont be excessive. Yanmar 4Lha Dtp Plus A CastAnd Yanmar has kept a reliable OHV design with gear-driven pushrods plus a cast-iron cylinder block and head, even though freshwater (heat exchanger) cooling is standard. Just as well since few owners would want the drag of keel cooling pipes in a semi-displacement hull. The 2kW starter motor is mounted above the engine bearers and away from bilge water, though a well-maintained boat should never have more than a puddle in the bilge. The Kanzaki box has reduction ratios from 1.67:1 to 2.43:1 ahead and astern, while the ZF63A ratios are 1.21:1 to 2.53:1. The 6LPA-STP2 engine is 1257mm long, though at 451kg with box its not much heavier. Like all mechanically injected diesels, the STP should not be run continuously below its maximum torque band or excessive injection advance could glaze the cylinder bores through unburned fuel. Mechanically injected diesels must be worked to maintain a long service life. Yanmar states the maximum continuous rpm is 3100 but Id recommend running at this rpm in calm water only and 2900 to 3000rpm would be better for maximum continuous operation. A Fairway 36 cruises at 12kt and 2400rpm and runs out to 18kt at wide-open throttle, whereas twin STP engines cruise a 13-metre Millcraft cat at 16kt, with WOT achieving 22kt. Millcraft states that 2.48:1 gear reductions are used while swinging four-bladed 22 x 22.9in props. Its not a marinised automotive engine nor does it have a combined cylinder block and head as with one of the direct competition. In my opinion that design is plain stupid how are the bores accessed should re-honing and oversize pistons be needed.
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