Evinrude 33 HP Ski-Twin Electric 20″ Long Shaft (1965) Outboard Motor Specifications & Maintenance Guide
The 1965 Evinrude Ski-Twin Electric Model 33553 represents the top-tier long-shaft configuration in Evinrude’s 1965 33 HP line. Engineered for 20-inch transoms on deeper hulls and pontoon boats, this 144-pound motor combines electric starting with a twin-cylinder 40.5 cubic-inch powerhead. Producing 33 horsepower at 4,500 RPM, Model 33553 features a full Forward-Neutral-Reverse gearshift, remote control integration, and Centri-matic water cooling.
To ensure smooth performance and reliable electric starting, regular technical inspection is essential. Key service parameters—such as setting breaker points precisely to 0.020″, gapping 14mm spark plugs to 0.030″, maintaining carburetor float level flush with the bowl rim, and inspecting lower unit pin integrity—directly preserve powerhead life and ensure instant starting on the water.
Maintenance Recap & Tune-Up Checklist
- Electrical & Ignition Check: Verify starter circuit wiring, adjust magneto breaker points to 0.020″, check condenser rating (.25–.29 mfd), and set Champion J4J or equivalent spark plug gaps to 0.030″, torquing to 20–20.5 ft-lbs.
- Fuel System & Choke Adjustment: Inspect the single-barrel float-feed carburetor, verify float rests flush with casting edge, set inlet needle clearance to 0.062″–0.065″, and test electric/manual choke operation.
- Gearcase & Water Pump Inspection: Servicing the Centri-matic water pump impeller regularly ensures proper cooling. Check lower unit oil level (12:21 gear ratio) and verify propeller drive pin (Part No. 304575, 1/4″ x 1-15/32″ stainless steel) is undamaged.
- Internal Tolerances & Overhaul Spec: During powerhead inspection, ensure crankshaft journals align with factory specs (Top: 1.2495″–1.2500″; Center/Bottom: 0.9995″–1.0000″; Crank Pin: 1.1823″–1.1828″) and verify standard 3.0625″ piston ring compressed tension (6–9 lbs).
Technical Specifications
| Specification Parameter | Details / Value |
|---|---|
| Model Number | 33553 |
| Model Year | 1965 |
| Horsepower (O.B.C.-Certified) | 33 HP @ 4500 RPM |
| Full Throttle Operating Range | 4000 to 5000 RPM |
| Engine Type | 2 Cylinder, 2-Cycle |
| Bore and Stroke | 3-1/16″ Bore x 2-3/4″ Stroke |
| Piston Displacement | 40.5 cu. in. |
| Starter Type | Electric (Ski-Twin Electric) |
| Transom Length | 20″ (5″ longer than standard) |
| Outboard Weight (Without tank) | 144 lbs. |
| Cooling System | Centri-matic (Combination positive displacement & centrifugal) |
| Ignition Type | Flywheel magneto |
| Spark Plug Type | AC-M42K, Champion J4J, Auto-Lite A21X (14mm) |
| Spark Plug Gap | .030 inch |
| Spark Plug Torque | 20 – 20-1/2 foot-pounds |
| Breaker Point Gap | .020 inch |
| Condenser Capacity | .25 – .29 mfd. |
| Carburetion | Single barrel, float feed, high/low-speed adjustments, manual/electric choke |
| Float Level Setting | Flush with rim of casting |
| Inlet Needle Seat | .062 – .065 inch |
| Fuel Capacity | 6 gallons, suction type tank |
| Fuel Tank Weight | 12 pounds net |
| Speed Control | Knob on steering bracket or remote (Synchronized throttle & spark) |
| Gear Shift Control | Forward, Neutral, Reverse |
| Propeller Gear Ratio | 12:21 |
| Propeller Drive Pin | Part No. 304575, 1/4″ x 1-15/32″ stainless steel |
| Propeller | 10-3/8″ diameter x 12-1/2″ pitch, 3 blade |
| Piston Ring Set – Standard | Part Number 378436 |
| Piston Ring Set – .020″ Oversize | Part Number 378437 |
| Piston Ring Set – .040″ Oversize | Part Number 378438 |
| Diameter of Ring (Standard) | 3.0625 in. |
| Width of Ring | .0925 – .0935 in. |
| Compression When Compressed | 6 to 9 lbs. |
| Piston Less Rings – Standard | Part Number 380039 |
| Piston Less Rings – .020″ Oversize | Part Number 380557 |
| Piston Less Rings – .040″ Oversize | Part Number 380558 |
| Crankshaft Top Journal | 1.2495 – 1.2500 in. |
| Crankshaft Center Journal | .9995 – 1.0000 in. |
| Crankshaft Bottom Journal | .9995 – 1.0000 in. |
| Connecting Rod Crank Pin | 1.1823 – 1.1828 in. |
Disclaimer & Information Notice: Specifications, fuel ratios, and maintenance guidelines listed on VintageMotorSpecs.com are compiled for historical reference and educational purposes only. Always verify data against an official OEM service manual prior to ordering parts or executing repairs. VintageMotorSpecs.com assumes no liability for repair errors, equipment damage, or personal injury resulting from the use of this data.
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