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Question for Joe

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rob

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Hi Joe...thanks for your help

Hi Joe...thanks for your help on my last flooding problem.....I need to find out what kind of RPMs my engine is running at full throttle...How do i find that out? I have no Tach on my boat...Can i hook one up? If so..Are they easy to hook up? I would appreciate any info you have...Thanks.


Rob
 
"Rob... You'll need to ref

"Rob... You'll need to refresh my memory as to what engine, year, and hp we're speaking of.

Joe
"
 
Sorry Joe...I have a 1975 Joh

Sorry Joe...I have a 1975 Johnson 70 HP....Has warm up lever and a toggle choke....I have no Tach or speedometer..so I have no idea what RPMs im running at full throttle. Thanks.


Rob
 
"Rob... That 1975 70hp Johnson

"Rob... That 1975 70hp Johnson hits its horsepower at 5000 rpm, and the top rated rpm is 5500 rpm. The desired rpm at wide open throttle would be between that 5000 and 5500 figure NOT OVER the 5500 figure!

The tachometer is quite easy to hook up but you must have one that is compatible with the Johnson outboard. The OMC tachs have a dial on the back that must be set to six (6) as they operate off the charging system.... and the charging system is a six (6) pulse setup.

On the tach, there's a purple, a gray, and a black wire. The purple wire is for 12 volts from the key switch when the switch is on. The black is naturally a ground. The gray is the pulse wire from the charging rectifier.

On the engine wiring harness or at a plug on the factory type OMC control box, there are the identical wires. Simply a matter of hooking the wires together.

Joe
"
 
Thank you Joe...your a big he

Thank you Joe...your a big help.....Can you tell me were to find that harness? Is it on the Cotrol console or is it inside the engine cover itself?....Thanks Joe.


Rob
 
"Rob.... The wiring harness I

"Rob.... The wiring harness I speak of is the group of wires that run from the engine to either a OMC Control Box, or to a area under a console, dashboard, whatever one might call it.

In the case of the OMC Control Box, you will see , most likely on the area facing the stern, a rubber plug. That plug has three holes in it (sockets) that accept a three pin connector (pins). Those three holes are the connections for the tach.... Gray,Black,Purple wires. The connections (wire colors) at the holes in the plug on the control box are:

.....Gray->o
Purple->o....o<-Black

The OMC type tachometers are equipped with a plug that you simply plug into that c/box plug.


In the case of a harness going to the console, etc, the wires will be protruding out of the visible harness there and will be obvious.

Joe
"
 
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