Mounting thermostat sensor

[titaniumneck]

Here is a picture of my M40C Tohatsu thermostat housing. Can I drill and tap this to put thermostat sensor for temperature gauge?

 

[Sea Rider]

If thinking a temp gauge will save future overheats due to impeller failure or lower leg water intakes obstructions, definitely not. Temp rises high and fast in a very short term specially at fast, wot throttle range that although detected by gauge will be too late, already will have fried impeller and probably damaged combustion head gasket as well. Upload pic of probe/sensor to see size, form, find a better attachment point.

Happy Boating

 

[titaniumneck]

I have removed thermostat awhile back, so that area is clear. That's why I was thinking it would be a good place to put sensor. It's such a compact motor that I do not know of any other place to put temperature sensor.

 

[Sea Rider]

That 40 needs to work with a thermo, combustion chamber will be warmed faster during cold starts along good operating temp at idle through wot range as well. What's the use of counting with a temp gauge, besides looking cool ? is it a digital round, square gauge ? you plan installing it on a dashboard if counting with a center console, on OB front cowl, tiller ?

Is it a screw type sensor, or one that can be bolted/attached/fixed to head ?

Happy Boating

 

[titaniumneck]

I haven't gotten one yet, I was thinking about just putting sensor with the overheat buzzer. Just don't want to warp another head or blow another headgasket.

 

[Sea Rider]

Will need to know which is the correct normal operating temp of that 40 at fast speed/wot throttle. Does the temp gauge has a heat refference at which temp will sensor trigger itself. If buzzer is inside gauge, will hardly hear it buzzing if installed on OB. Is the 40 HP equipped with a third water intake screen right under anticav plate ?

Happy Boating

 

[titaniumneck]

Ok, wow you're good. Let me try and find the temp specs on M40C Tohatsu, and what would that third water intake look like.

 

[Sea Rider]

Like doing crazy things on outboards, but would not dream about installing a thermo gauge on a portable OB. M40C service manual does not states working temp, probably Paul has an appropiate spec answer for that. If not, will need to get a heat gun, the ones you aim at a point you want to heat measure, in this case at cylinder head to know working temp while at wot. Once correct temp is known will need to adjust gauge, if adjustable one, to some heat degrees more to detect an overheat for buzzer to start buzzing. Bit complicated, colud turn out into a costly experimentation.

The idea could be cool, but it's not same as counting with a proper heat spot around head, say removing a bolt to screw sensor there...

That OB doesn't have a third lower water intake, this one will prevent any overheat condition if lower leg happens to catch any unwanted floating debris, kelp, plastic bags and both side water intakes are completely obstructed. Luckily my 18 has one, which love.

Happy Boating

 

[pvanv]

That motor needs a thermostat, or the plugs will foul from being too cold for too long during warm-up. Block temp will be around 150F, head a little warmer perhaps. Unless the temp sensor will kill the motor, it will be useless. The motor would cook before you would notice the needle.

 

[titaniumneck]

I know to some a little M40C is not enough motor to put too much effort into, or experiment with, but it is all I have and with my disability retirement check being what it is, this little motor is golden to me. Steering wheel, remote box controls, and electric start which I am unable to pull start a motor. And I can barely afford to fix it, much less replace it. So I want to do whatever I can to keep it up and running. 35 mph is plenty for me to get down the Bayou. Paul you are right, I will find one that will kill engine when to hot. Thank you sir.

 

[Sea Rider]

Moons back fabricated a metal mount and attached a thermo fuse, don't remember the heat range, was mounted directly on head of a Evi 15 HP. Solved 2 overheat conditions while kelp boating, (lower leg water intake kelp blockage) Worked fantastic well shutting down OB when begining to overheat due to impeller or thermostat failure. Down issue needed to carry a spare wire jumper to ground back IC ground to powerhead when thermo fuse blew. This was the cheapest overheat control ever.

Happy Boating

 

[titaniumneck]

Thanks a lot. I will start looking up some information on this and try it out. Thanks again.

 

[Sea Rider]

CL, good news, check this, should be an easy install....

https://www.hardlineproducts.com/product/digital-powersports-thermometer-gauge/

Happy Boating