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General Information
Preparations For Starting
Before Starting
Starting Engine
Engine Break-in and General Running
Stopping the Engine
Decompression Lever
Instrument Panel
Wiring Diagram
Preparing Engine for Storage
Preparing Engine for Spring Service
Fuel Injection Timing
Diesel Valve Timing
Adjusting Fuel Timing
Decompression Device Adjustment
Fuel System
Fuel Bleeding
Oil Filter Change
Sea Water Pump and Impeller Replacement
Model 15 Sea Water Circulation Diagram
Model 12, 18, 20, 25, 25XP, 30, 40 & 50 Water
Fresh Water Circulation Diagram

Hurth Transmission
Periodic Service Chart for Engine
Marine Engine Warranty - Limited

Engine Specifications and Images
(by engine model)




For long dependable service, become familiar with the operating requirements of your engine. All Universal Diesel engines are completely factory tested under load conditions before shipment.

In preparation for starting engine, oil must be added to the crankcase. Refer to specifications for lubrication, oil type and capacity. Recheck oil level on dipstick, it should be to full mark, do not overfill, when checking oil remove dipstick, wait 15 seconds, then recheck.

The oil level should be checked before the first start-up each day. Dipstick has high and low markings. Oil levels either above or below these marks should never be allowed. Oil is put into the engine by removing the screw cap on the top of the rocker arm cover. Fill the crankcase with oil to the upper mark on the dipstick and securely replace the filler cap.

THE TRANSMISSION IS SHIPPED WITH OIL, BUT SHOULD BE CHECKED PRIOR TO OPERATION.  Refer to specification of oil type and capacity. Recheck oil level on dipstick. (DIPSTICK TO BE INSERTED ONLY. DO NOT SCREW IN). See transmission instructions for additional information. FILL TO INDENTED RING ON DIPSTICK only.

An unrestricted water supply must be provided to the engine. Use a minimum of 1/2" through hull fitting. Locate the scoop where it will have a full supply of water at all times regardless of running position or rough seas. A sea cock or gate valve is necessary at the water inlet point. The water pump has a 318" N.P.T. suction inlet.and the heat exchanger has a 3/8" N.P.T. water outlet. Use a non-collapsible hose for the suction side. A water strainer installed in the line ahead of the water pump aids in preventing clogging of the cooling system. The exhaust pipe is 1-1/4" N.P.T: on all models except M-50, which is 1-1/2" N.P.T.

The fresh water manifold on all models except M-1 5 should be filled slowly to the bottom of the filler cap. A 50/50 mixture of fresh water and antifreeze solution is acceptable as an all weather coolant, eliminating the need to drain the fresh water system for cold weather operation or storage. A coolant mixture may change based on climatic conditions in your area. The rust preventive will aid in reducing rust formation if no antifreeze is used.

Model 15, being sea water cooled, draws its water directly from the sea, filling the engine system and discharging the hot water overboard into the exhaust line.

Be sure water pump is lubricated by turning grease cup (if provided on your engine) clockwise 1/2 turn at 30 hour intervals. Pumps with no grease cup do not require lubrications.

Transmission shifting controls must allow the clutch to engage in the full forward and reverse positions. Restricted or partial engagement will cause undue wear. The transmission should always be in the neutral position before starting the engine. Also, the transmission shifter arm must be at a 900 angle to the transmission bracket cable when in neutral.


On all models, the fuel line must be connected from the fuel tank to the electric fuel pump, then to the fuel filter. On Model 15, connect directly to the fuel supply line. A fuel return line must be connected from the injector nozzles to the top of the fuel tank so that the unused fuel can blow back into the fuel tank. IT IS VERY IMPORTANT TO KEEP ALL FUEL LINES FREE OF DUST AND IMPURITIES. THEREFORE, BLOW OUT LINES BEFORE CONNECTING.

Check fuel supply and make sure fuel lines are tight. Any fuel leakage must be corrected before any attempt to start the engine. If fuel line leaks are discovered or any work is done on the fuel system, it may be necessary to bleed the fuel system before the engine will start. (Refer to bleeding instructions in this manual if that procedure becomes necessary.)

Check all electrical connections. A wiring diagram is included in this manual. GROUND IS NEGATIVE and the ground terminal should be connected to the engine block. Make sure it is metal to metal contact, and securely tightened. Also, check the battery to be sure all cells are covered with electrolyte. Do not allow flames or sparks near battery openings. Gases produced during normal battery charging are EXPLOSIVE.