Use two temp senders on a V block outboard?

[Mark42]

Was looking at the power head on the 2003 Johnson V4 outboard to determine where to put a temperature sender for a temp gauge. It has 1/8" NPT "ports" on both heads. I noticed that each head has its own thermostat, and that started me thinking that one bank could have thermostat failure and run hot when the other bank is running normal. So a single temp sender would have a 50/50 chance of reporting a problem like that. Although the System Check should be triggered if either bank starts to over heat.

Started wondering if a sender should be installed on each head and run up to the temp gauge with a switch to flip/flop back and forth between heads? Would it provide any useful function to be able to monitor each bank independently?

 

[JustJason]

Re: Use two temp senders on a V block outboard?

Alot of them do have twin temp switches, 1 in each head. I couldn't tell you which year and which block J/E do them on, but it's been done. What I would do is first see if the other bank will hold a temp switch, and if it does, press on into the head and wire it in parralell to the other temp switch, (i believe its a tan wire)

 

[dingbat]

Re: Use two temp senders on a V block outboard?

200 HP Evinrude Ocean Pro
Two temps sensors, both hooked into the Check System Alarm.

Don't have a temp gauge. Don?t see a need for one. Overheating in outboards is rare.

I monitor water pressure gauge instead. IMHO a better overall diagnostic tool for the cooling system.

 

[Mark42]

Re: Use two temp senders on a V block outboard?

200 HP Evinrude Ocean Pro
Two temps sensors, both hooked into the Check System Alarm.

Don't have a temp gauge. Don?t see a need for one. Overheating in outboards is rare.

I monitor water pressure gauge instead. IMHO a better overall diagnostic tool for the cooling system.

Yes, the V4 90 hp has the same two sensors for the System Check, but that is only a warning after the fact that temps have risen to a dangerous point. A temp gauge will let me know ahead of time that temps are rising. I have had overheating problems on a few occasions, one caused $900 in repairs.

The old MFG w/40 hp twin has a temp and pressure gauge. I'm thinking same as you that for the V4, the pressure might be the better way to go. Seeing as the system check does have sensors in both heads, a pressure gauge in one cylinder head will monitor pressure throughout the entire system (right?).

 

[Haffiman]

Re: Use two temp senders on a V block outboard?

Temp gauges in some outboards might be a bit confusing.
Most of the Evinrude/Johnson runs at lower temp at 3/4 - full speed than idling due to the design and calibration of the by-pass system.
A pressure gauge is of more value and gives an earlier indication of when to change impeller which is quite a bit sooner than most people are aware of.

 

[JustJason]

Re: Use two temp senders on a V block outboard?

I'm with haffiman. Water pressure gauges work just as good. Wicked easy to install as well.

 

[dingbat]

Re: Use two temp senders on a V block outboard?

Yes, the V4 90 hp has the same two sensors for the System Check, but that is only a warning after the fact that temps have risen to a dangerous point. A temp gauge will let me know ahead of time that temps are rising. I have had overheating problems on a few occasions, one caused $900 in repairs.

The old MFG w/40 hp twin has a temp and pressure gauge. I'm thinking same as you that for the V4, the pressure might be the better way to go. Seeing as the system check does have sensors in both heads, a pressure gauge in one cylinder head will monitor pressure throughout the entire system (right?).

It's not a warning after the fact. The Check System will put the motor in S.L.O.W. long before you get to a dangerous level.

A pressure gauge measures the pressure of the entire system. The pressures you are dealing with are relatively small, 0-30 psi, so subtle changes show up well. You can even tell when the thermostats opening and closing by watching the pressure move up and down. Once you learn how the motor behaves, it is easy to see a cooling anomaly long before you would see it in the head temperatures.

A pressure gauge also helps with your maintenance. I stopped changing my water pumps on a regular schedule long ago. I now change my pumps on an ?as needed? basis.