In 2018, Yamaha announced a 425 hp V8 outboard engine. A very high output, rarely matched at that time in outboards. This series, christened XTO for Xtreme Thrust Output, offered thrust and torque superior to other engine manufacturers. This large 5.6-liter atmospheric (i.e., uncompressed) V8 was designed for large units capable of supporting its weight on the transom, and requiring torque to lift off.
Out with the 425, in with the 400 and 450!
For 2023, Yamaha has revised its copy and is proposing 450 and 400 hp engines on the same V8 base. Gone is the 425hp, replaced by these new power ratings. To gain the extra power, the Japanese manufacturer has worked on the surface finish of friction parts.
These engines feature very high compression, synonymous with high torque. The engine is fed by high-pressure injectors installed directly in the combustion chamber. In this way, injection can be varied according to demand, offering the best possible combustion. Exhaust and air intake are still handled by valves, 4 per cylinder for a total of 32 valves. The overhead camshafts are linked together by a chain, itself driven by a belt.
Silence, we're sailing!
A major effort has been made by the engineers to reduce engine noise. Despite their high power output, these outboards are very quiet. However, the characteristic V-engine noise, even more so in the V8 version, can be heard at high revs, for the pleasure of the boater.
Trials on several boats
We were able to test these engines on several hulls, whether single-engine on a RIB, twin-engine or even three-engine on a Capelli 44. Each time, the thrust is strong, but never violent. These engines have a fairly linear curve, making them very smooth to drive. Performance is there, but never extreme.
On a Capelli 900 RIB, for example, powered by a 400 hp XTO, maximum speed at 5950 rpm is 45 knots. Maximum fuel consumption is 126 l/h. Cruising speed is 3000 rpm at 19.2 knots, with fuel consumption of 33 l/h.
Other figures this time, with 3 x 450 hp on the longer, but also heavier Tempest 44, top speed in fine seas was 55 knots at 6,000 rpm. This time, the 3 engines consumed 412 l/h. Cruising at 3500 rpm, speed was 28.9 knots, with consumption of 140 l/h for the 3 engines.
Available in September 2023
These 400 and 450 hp engines will be available on the French market from September 2023. We'll let you know about prices shortly.
