3A0-76079-0 Tohatsu COLLAR, 8.2 - 9 - 7.5

Measurement Of Pressure In Inlet Manifold
The efficiency of an engine can be checked. Compare the pressure in the inlet manifold with the specifications that are given in the Fuel Setting and Related Information in the TMI (Technical Marketing Information). This test is used when there is a decrease in horsepower from the engine, yet there is no real sign of a problem with the engine. The correct pressure for the inlet manifold is given in the TMI. Development of this information is done with these conditions:
96 kPa (28.8 inches of Hg) dry barometric pressure
29°C (84°F) outside air temperature
35 API rated fuelAny change from these conditions can change the pressure in the inlet manifold. The outside air may have a higher temperature and a lower barometric pressure than the values that are given above. This will cause a lower horsepower and a lower inlet manifold pressure measurement than the pressure that is given in the TMI (Technical Marketing Information). Outside air that has a lower temperature and a higher barometric pressure will cause a higher horsepower and a higher inlet manifold pressure measurement.A difference in fuel rating will change horsepower and the pressure in the inlet manifold. If the fuel is rated above 35 API, the pressure in the inlet manifold can be less than the pressure that is given in the TMI. If the fuel is rated below 35 API, the pressure in the inlet manifold can be more than the pressure that is given in the TMI. BE SURE THAT THE AIR INLET OR THE EXHAUST DOES NOT HAVE A RESTRICTION WHEN YOU ARE MAKING A CHECK OF THE PRESSURE IN THE INLET MANIFOLD.
Illustration 1 g00322855
Pressure Test Location (Typical Example) (A) Pipe plug.In order to check the inlet manifold pressure, remove the 1/2-14-NPTF pipe plug (A). Connect the 1U-5470 Engine Pressure Group to this opening in the inlet manifold.This tool group has a gauge to read pressure in the inlet manifold. Special Instruction, SEHS8524 is with the tool group and gives the instructions.
Illustration 2 g00284796
1U-5470 Engine Pressure Group (1) Pressure indicators. (2) Zero adjustment screw. (3) Pressure indicator. (4) Pressure tap. (5) Pressure indicator.Measurement Of Exhaust Temperature
Use the 1U-8865 Infrared Thermometer in order to check the exhaust temperature. The Operating Manual, NEHS0510 for the 1U-8865 Infrared Thermometer gives complete operating and maintenance instructions for this tool.Individual cylinder head exhaust temperatures can be checked with the 4C-6090 Temperature Selector Group, the 6V-9130 Temperature Adapter, and the 6V-7070 Digital Multimeter. Refer to Operating Manual, NEHS0537 for the complete operating instructions for the 4C-6090 Temperature Selector Group .Crankcase (Crankshaft Compartment)
Pistons or rings that have damage can be the cause of too much pressure in the crankcase. This condition will cause the engine to run rough. There will be more than the normal amount of fumes coming from the crankcase breather. This crankcase pressure can also cause the element for the crankcase breather to have a restriction in a very short time. This crankcase pressure can also be the cause of any oil leakage at the gaskets and at the seals that would not normally have leakage.Compression
An engine that runs roughly can have a leak at the valves. An engine that runs roughly can also have valves that need an adjustment. Removal of the head and inspection of the valves and valve seats is necessary to find those small defects that do not normally cause a problem. Repairs of these problems are normally done when you are reconditioning the engine. Cylinder Heads
The cylinder heads have valve seat inserts, valve guides, and bridge dowels that can be removed when the parts are worn or damaged. Refer to Disassembly And Assembly for the replacement of these components.Valves
The removal and the installation of the valves is easier with use of the 1P-3527 Valve Spring Compressor .Valve Seat Inserts
Use the 6V-4805 Valve Seat Extractor Tool Group for the removal and the installation of the valve seat inserts. Lower the temperature of the insert before the inset is installed in the head.Valve Guides
The tools for the removal and the installation of the valve guides are the 5P-1729 Valve Guide Driver Bushing and the 7M-3975 Valve Guide Bushing Driver. The counterbore in the driver bushing installs the guide to the correct height. Use a 1P-7451 Valve Guide Honing Group in order to make a finished bore in the valve guide after the guide is installed in the head. Refer to Special Instruction, SMHS7526 for an explanation for this procedure. Grind the valves after the new valve guides are installed. Checking Valve Guide Bores
Use the 5P-3536 Valve Guide Gauge Group in order to check the bore of the valve guides. Refer to Special Instruction, GMG02562 for the instructions for the use of this tool.
Illustration 3 g00285313
5P-3536 Valve Guide Gauge Group Bridge Dowels
Use a 5P-0944 Dowel Puller Group and a 5P-0942 Dowel Extractor. Remove the bridge dowels. Install a new bridge dowel with a 6V-4009 Dowel Driver. This dowel driver installs the bridge dowel to the correct height. Valve Lash
Valve lash is measured between the rocker arm and the bridge for the valves. All of the clearance measurements and the adjustments must be made with the engine stopped. The valves must be FULLY CLOSED. Valve Lash Check
An adjustment is NOT NECESSARY if the measurement of the valve lash is in the acceptable range. The range is given in Table 1.
Table 1
Valve Lash Check: Engine Stopped    
Valves     Acceptable Valve Lash Range    
Inlet    
0.42 to 0.58 mm (.017 to .023 inch)    
Outlet    
0.92 to 1.08 mm (.036 to .043 inch)