Evinrude Ocean Pro 175 '98 in slow mode

[gam101]

Gee, that temp sensor should have a plastic hex head "nut" holding it to the block. Yours looks to be broken off. If you have a voltmeter (ohmmeter), test the tan/blue wires on each of the two sensors for continuity to ground, with the engine cool. If either is grounded, that sensor is bad.

The fact that your temp sensor "nut" looks to be broken off, is suspicious.

I would test/replace the thermostats, if the sensors test OK.

Appreciate that voltmeter suggestion. I am planning to use it to test that sensor. At the moment, the sensor in the picture is disconnected. I guess you are recommending I reconnect it, and then power up the OB (without starting it), then test with the voltmeter. Please confirm.

 

[gam101]

Besides all the patched wiring with tape....if the motor go hot enough to melt pack it has melted the "salt shaker" t-stats in heads......

Appreciate the help. "Salt Shaker" ? "T-Stats"? I'm totally lost now. :facepalm: I did issue a "newbie" alert in the first post.

I tried to google those terms too & nada. I apologize, it's my first boat, and I am still learning. :blue:

Is this what you meant?

https://www.amazon.com/Thermostat-Johnson-Evinrude-75-175hp-1993-2006/dp/B01M0WZ7HG

 

[gam101]

Gee, that temp sensor should have a plastic hex head "nut" holding it to the block. Yours looks to be broken off. If you have a voltmeter (ohmmeter), test the tan/blue wires on each of the two sensors for continuity to ground, with the engine cool. If either is grounded, that sensor is bad.

The fact that your temp sensor "nut" looks to be broken off, is suspicious.

I would test/replace the thermostats, if the sensors test OK.

Appreciate the reply.

I should mention that according to the mechanic, currently the OB has good tell-tale flow & he said it is not overheating. When he said that, I remember him putting his hand on the head while the OB was in a barrel & running.

 

[gam101]

Thermostats are under the hex shaped housing above the spark plug. But i wouldnt go opening them up and risk damaging the o ring unless you know they are the problem. Feel both heads, are they a similar temperature, that will tell you if one thermostat has broken, to have two go down at the same time would not be very likely. I think you need to run it at idle on muffs or in a barrel and check temperature on both heads and then develop a plan.

Yes that middle thing is the overheat switch unit, ive never had to replace one so not sure how thats done but it definitely looks like you dont have to remove the head so keep your wrench in its holster for a while longer before embarking on that as someone else will know

Ok, so if the thermostats are below the housing, then if I am not mistaken, that housing has a gasket.

Below that housing is the head that the mechanic removed, and replaced the piston o-rings. Please correct me if I am wrong about the location of the thermostats.

I am going to look at the thermostats at the very end, following the "hand on the head in idle for heat" check & the voltmeter check for the temp. sensor.

 

[racerone]

???----" piston o-rings "--------There are no rubber o-rings on the pistons.-----There are o-rings that seal the cylinder head to the block instead of a head gasket.

 

[gam101]

???----" piston o-rings "--------There are no rubber o-rings on the pistons.-----There are o-rings that seal the cylinder head to the block instead of a head gasket.

Yes, that is what I meant, but failed to explain. There is a gasket above the head, in the housing with the plugs. That is where I am assuming the thermostat is. The mechanic did say that the gasket was fine in that housing.

 

[Faztbullet]

Is this what you meant?

https://www.amazon.com/Thermostat-Jo.../dp/B01M0WZ7HG
Yep........

 

[Bosunsmate]

I thought it was an o ring with the thermostat housing too but doesnt matter you can report on that if you do need to open it up, but as has being said if your motor did get really hot then they may have warped and so its probably best to check them over anyhow.
You will never regret having done extra checks when you a speeding around on the water miles from the ramp

 

[Bosunsmate]

thermostat housing is directly above the top sparkplug on both cylinders by the way, you definitely dont remove the whole metal head

 

[gam101]

thermostat housing is directly above the top sparkplug on both cylinders by the way, you definitely dont remove the whole metal head

Could you please review the image attached. Am I pointing to the right location of the thermostat?

Thanks again.

 

[Chris1956]

Yes, that is the cover over the thermostat. Use a large wrench on the larger hex head. The smaller hex head can break off, especially if the motor has seen some salt.

The thermostats on my '98 Johnny 150HPV6 needed replacement last spring. They had stuck open. if your's have never been changed, that may be a problem.

 

[gam101]

Yes, that is the cover over the thermostat. Use a large wrench on the larger hex head. The smaller hex head can break off, especially if the motor has seen some salt.

The thermostats on my '98 Johnny 150HPV6 needed replacement last spring. They had stuck open. if your's have never been changed, that may be a problem.

Thank you sir.

 

[gam101]

Gee, that temp sensor should have a plastic hex head "nut" holding it to the block. Yours looks to be broken off. If you have a voltmeter (ohmmeter), test the tan/blue wires on each of the two sensors for continuity to ground, with the engine cool. If either is grounded, that sensor is bad.

The fact that your temp sensor "nut" looks to be broken off, is suspicious.

I would test/replace the thermostats, if the sensors test OK.

Wanted to you let you know that looks like both the sensors are bad. I hooked up the tan wire to the red on the multimeter, and the white to the black, the buzzer went off on the continuity setting while the OB was not running. Going to keep this simple but effective test in mind. Appreciate the help.

 

[Faztbullet]

No you check to ground....red lead to tan and black to engine block...same for white. Tan is heat alarm and white is Quikstart

 

[gam101]

No you check to ground....red lead to tan and black to engine block...same for white. Tan is heat alarm and white is Quikstart

Appreciate the help again. So, I followed the instructions & have attached pics too.

I can only test the left heat sensor because it has both the wires. And during it's test, the multimeter's buzzer did not sound off on either the tan or the white wire. In each wire's case, I hooked up the meter's red to the respective wire & the meter's black to the engine block.

I think the test implies the left heat sensor is bad too. The right sensor is missing the white wire (bad).

Any pointers on how to get the sensors out without unbolting the top engine cover? Removing the top engine cover will require a gasket replacement.

 

[racerone]

Your testing assumptions may be wrong.----The motor left the factory with 2 different sensors !----Cylinder head does NOT need to come off to replace those sensors.

 

[gam101]

Your testing assumptions may be wrong.----The motor left the factory with 2 different sensors !----Cylinder head does NOT need to come off to replace those sensors.

2 different ones? I did not know that. I thought left & right were identical. Attached is the pic of the port side sensor I just got from the dealer. The last one they had. So I still need to get the right side.

I just realized the wiring on the new one is totally different from the one on the motor (posted pics above). :facepalm:

Yep, someone already mentioned here that I do not have to remove the head for sensors. Thing is, as they pics convey, the plastic nut is broken, the sensors are stuck & all I have for leverage to pull the heat sensors out are fragile wires. Hence my question.

Appreciate the help.

 

[Faztbullet]

The one with 2 wire tests ok if you tested like I posted, and that goes for the single wire one also. No buzz is good ,buzz is bad.

 

[gam101]

The one with 2 wire tests ok if you tested like I posted, and that goes for the single wire one also. No buzz is good ,buzz is bad.

Well I tested with the meter's red onto the sensors each wire (left sensor), and the black on the engine block. And yes, no buzz.

Now I am wondering why the sensors are screaming overheat while they appear ok. :facepalm: Thermostats malfunction?

Appreciate the correction to my assumption that the sensors were bad.

 

[CatTwentyTwo]

Just for the heck of it, try switching your meter to the 200 or 2K ohm setting instead of buzz and see if you get any reading on the tan sensor wires.
I pulled the sensor out of my 94 175 motor and it's just a blind hole so removing the head isn't going to do you any good.

edit: It wouldn't hurt to go even higher on your meters ohm scale and check for a reading, I'm not sure what it would take to trigger slow mode.
Good luck