Silver Wraith 8.1L 430bhp

V8 Small Block Chevy 496cid

8.1L 430bhp V8 Performance Marine engine rebuilds This engine is literally the pride and joy of our technical director Dave Martin. Developed in constant consultation between himself and David Vizard to specifically meet the needs of Greg Copp, Technical Writer for Motorboat & Yachting magazine. It is a superb choice for the discerning owner of a larger boat, 35ft+. Greg has a 43ft Sunseeker Thunderhawk which weighs in at 7.5 tons, and was very thirsty. Swaymar have always maintained that, especially for larger heaver boats the 496 cid is actually a better engine than the 502 cid commonly offered.

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8.1L 430bhp V8 Performance Marine engine rebuilds Despite being slightly smaller in capacity (all be it only 98cc) the 496 achieves its 8.1 litre by using a smaller bore but longer stroke than the commonly offered 502, and while the big bore short stroke of the 502 may be ideal in the cars and trucks they were designed for, they develop their power further up the RPM range, not a problem in a vehicle with gears. We recognise that boats, especially heavier ones, benefit from as much power and torque as low down the RPM range as you can get it. Figures commonly quoted for 502's are 420 BHP @ 5200 RPM. Because of its longer stroke, our Silver Phantom 496 makes 431 BHP and an awesome 521 ft. lbs of torque almost a thousand RPM lower @ 4350 RPM. in fact it topped the magic 500 ft.lbs of torque at just below 3000 RPM. This is a petrol engine that dwarf's many turbo diesels, yet because of the hugely increased efficiency, at cruising speeds can actually save fuel over the standard 330 BHP units. These carefully considered engineering improvements result in a considerably faster boat but without the usual fuel penalties associated with more power.


  • Mercruiser
  • Volvo Penta
  • Indmar
  • any boat running Chevy V8s

Whilst fine on Volvo Penta Duo-prop legs, in Mercruiser applications it is recommended not to use legs of less than Bravo 2X or Bravo 3X specifications.


All of our engines include a free inlet manifold inspection and reconditioning to 'as good as new'.
Note: If prior to inspection your existing manifold is un serviceable, a new one will be required.

  • Fresh water cooling system
  • Stage 1 performance marine camshaft
  • Full refurbishment and re assembly of existing ancillaries


Most but not all engines that are sea water cooled will require a new block upon rebuild.

  • Re-manufactured block
  • Brand new block


  • 1 year limited warranty,subject to the fitting of a new or refurbished inlet manifold and new cast iron exhaust manifolds
  • 2 years limited warranty when fitted with 1 piece stainless steel exhaust manifolds

Not Included

  • *New Cast iron exhaust manifold*
  • *New Inlet manifold*


Performance Marine engine rebuilds We strongly recommend to all of our customers to consider trying a 1 piece stainless exhaust system and do away with the fear of leaky cast iron ones ruining your engine. You can find more detailed information on stainless steel marine exhausts as well as independent articles written by marine surveyors on the pit falls of cast iron manifolds at

Propeller Pitch

V8 Performance Marine engine rebuilds Depending on boat, in order to prevent over-revving, and feel the full effect of its extra torque, this engine may need to carry a larger diameter or coarser pitch propeller.

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Displacement 496 CID (8.1L)
Engine Type V8
Peak Torque 535-545 ft lbs @ 4250 RPM
Torque Range 500+ ft lbs @ 2750 - 4500 RPM
Bore & Stroke 4.310" X 4.250" (109.5mm X 107.95mm)
Compression Ratio 9.5:1
Camshaft Stage 2- Specially developed marine camshaft - delivering more torque at lower rpm.
Major Components Steel crankshaft, forged competition con rods, and performance pistons.
Head & chamber work Moderate reshaping of combustion chambers and cylinder heads - Improve gas flow and increase torque.
Cooling System Closed fresh water cooling, Long Life 5-Year Anti-Freeze, 20 year long life silicon hoses - Protecting your engine from the inside out.
Advanced Engine Lubrication System Expertly modified oil galleries provide greatly improved lubrication to the camshaft, cam followers, gears and timing chain - For optimum engine longevity.
Dimensions (LxWxH) in 43x 30 x 22
Dimensions (LxWxH) mm 1092 x 740 x 559
Weight (lbs./kg) 948/431
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