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O.S. - OSMG1622 OSM13952 13952 531028022355 4531028022355
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O.S. 21XZ-M Speed 3.5cc Inboard Marine Engine
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O.S. 21XZ-M Speed 3.5cc Inboard Marine Engine
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Tech Notes
This is the O.S. Speed 21XZ-M Inboard Marine Engine.

****** Because of the competition nature of this engine,******
******it is NOT covered by the O.S. 2 Year Warranty.******


DLC (Diamond-like Coating) on crankshaft, plus tungsten weights to
minimize vibration, and silicone inserts to smooth fuel mixture
21D big-bore carburetor allows the use of high nitro fuel
Laser engraved water cooled cylinder head


21XZ-M Speed Inboard Marine Engine with RP7 Glow Plug, Exhaust Seal
Ring, Dust Cap, Head Gasket Set and Instruction Manual


Fuel: Boat blend with 10-30% nitro content (20% recommended for break
Exhaust system depending on application
Glow starter and shore equipment


Displacement: 0.213 cu in (3.49 cc)
Bore: 0.641" (16.27mm)
Stroke: 0.661" (16.8mm)
Practical RPM: 4,000-45,000
Output: 2.76 hp @ 33,000 RPM
Weight: 10.85 oz (307.5 g)
Crankshaft Size: 1/4-28
Carburetor Settings:
Needle Valve; Turn clockwise until closed, open 1.5 turns, close
10-15 after running hull through 1 tank of fuel, repeat until
approximately 2 liters of fuel have been consumed
Mixture Control Valve; After getting needle valve adjusted, turn
clockwise or counterclockwise in 10 increments to reduce
excessive smoke (too rich) or to reduce speeding up momentarily
(too lean)

Distance between mounting hole centers same side: 0.83" (21mm)
Distance between mounting hole centers opposite side: 1.4" (37mm)
Distance/mounting tab to center of exhaust: 1.1" (28.5mm)
Distance/mounting tab to center of cooling inlet: 2.2" (55.05mm)
Distance from exhaust center to mounting flange bottom:
Width not including mounting flanges: 1.2" (31.6mm)
Width including mounting flanges: 1.8" (45mm)
Height bottom of crankcase to top of intake: 3.1" (78mm)
Length from Front Bearing/end of Crankshaft: 0.87" (22mm)
Length from Front Bearing/center of Crankcase: 1.7" (44mm)
Length from Center of Crankcase/end of Crankshaft: 2.6" (66mm)

jxs 12/03/12

– If you need more information, use these O.S. resources –
Email: enginesupport@hobbico.com
Web Site: http://www.osengines.com/
Phone: 217-398-8970
  Postal Address:

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Accessories Needed
This is the O.S. Speed 21XZ-M Inboard Marine Engine. FEATURES: 21D big-bore carburetor allows use of high nitro fuel, Diamond Like Coating on silicone filled tungsten weighted crankshaft for optimum balance, RP7 turbo glow plug, laser etched water cooled head REQUIRES: 10-30% nitro boat fuel, glow starter, shore equip.

Accessories for the O.S. 21XZ-M Speed 3.5cc Inboard Marine Engine

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  Special Stock Number Product Description Parts Saver Eligible Tower's
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 LXZUK6 AquaCraft GrimRacer 30% Boat Fuel Quart
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11.99   In Stock
Subtotal for this Group of Accessories: 11.99  

Primary Accessories   Building & Field Equipment Optional Accessories

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