4. When the current draw of the electronic device is between 4 and 20 amps, use a suppressor(G) rated at 20 amps. The suppressor(G) has 27 turns of #10 gauge wire. The inductance should be from .44 to .55 millihenrys at 450 to 550 KC. Use an electrolytic capacitor (H) (1000 MFD, 25 WVCD).

  Bonding "Non-Current" Carrying, Metal Parts

A proper bonding system is important to both radio noise suppression and to prevent electrolytic corrosion. The following reprinted with permission from the American Boat and Yacht Council's Standard E-l "Bonding of Direct Current Electrical Systems.

1. There should be a common bonding conductor (I) which connects the non-current carrying metal parts of the electrical accessories (J), the marine rectifier (K), a ground plate (L), and the fuel tanks (M).

2. The engine ground terminal (N) of both port (0) and starboard (P) engines should be connected to (I) unless the negative battery lead carrying starter current (O) is so connected.

3. The batteries (R) in lead lined battery trays or metal hold downs (S)  which are also connected to (I).

4. Any driveshaft couplings (i) should have a jumper (U) to assure electrical continuity.

5. Additionally, wires should be adjacent to each other throughout the system. Electrical equipment may be internally grounded. Switchboard and metal distribution panel cabinets should be connected to (I).

   Shielding Instrument Cable Emissions

Interference can be radiated from the engine to instrument cable. These are listed in order of the most likely noise makers, and a suggestion of what may help to reduce the interference.

1. Disconnect gray tachometer lead (V) at the terminal strip to determine if this wire is the source of noise.

2. If so, install a .5 MFD bypass capacitor P/N 378491 (W) to this terminal and to ground (X).

3. Reconnect tachometer wire. Do not connect the gray tachometer lead if the alternator tachometer is not being used. If tachometer lead is not used tape end to insulate.

   Covering Ignition System with Brass Screening

1. If RF interference needs to be reduced further: Install brass screening covering cylinder heads which will cover the ignition coils, spark plugs and the high tension leads.

2. Screen must be grounded to powerhead completely around items, on both port and starboard sides.

      Four Cycle Engines

Install Suppressor Type Leads and Resistor Spark Plugs
Install resistor type spark plugs (A) in engine if engine is equipped with standard spark plugs.

Suppression Plug

AC         MR43T
Champion   RBL 8

Check the high tension leads between spark plugs and distributor cap (B) and distributor cap to ignition coil (C) for defective leads. Check the resistance of each high tension lead with an ohmmeter (if suppressor type high tension leads (D) are used). The resistance of the leads should be approximately five thousand (5,000) ohms per foot. Replace defective leads. If engine is not equipped with suppressor leads, the addition of these leads will help eliminate more of the ignition radiation.