Temp Sender not fitting 100%

[phillnjack2]

I have just got myself a temp guage and sender for my 1995 evinrude 60hp.

The pre-drilled and tapped hole is already on these engine for a temp sender, so i got one to fit the thread. ( 1/8th npt )

The problem is i have measured the depth of the hole and the depther the sender sender goes in.

There is a gap of around 3mm (1/8th inch) from end of sender to the cylinder head itself.

Now would it be best to place a small disc of aliminium or steel in the hole to build up the metal to
sender contact.

If the sender was 4 mm longer it would touch the cylinder head ofcourse, but they dont seem to come at this length.

or could i simply put oil or water in the hole as it would be sealed once sender is tightened up.
The oil or water would probably come upto the same temp as the cylinder head OR WOULD IT ?

any advice would be welcome on this.

pic below to help explain my problem.





phill

 

[Joe Reeves]

Re: Temp Sender not fitting 100%

On the earlier models that do not have the predrilled hole but rather use a "L" shaped bracket attached to one of the cylinder head bolts that the sensor screws into, it has always been best to leave a .010 space between the end of the sensor and the cylinder head in order to avoid a false reading. Taking this into consideration, the heat reading of the engine was being read by the sensor thru that .010 gap of ambient air and the conductive qualities of the "L" bracket.

Think about it...... that hole in your cylinder head is drilled that deep for a reason.

 

[metriccrescentwrench]

Re: Temp Sender not fitting 100%

It's been exceedingly seldom that I've ever disagreed with Joe, but here goes. I'm an engineer and have worked with industrial control and automation for over 20 years, so I've had to do a fair amount of temperature measurement applications. To get the most accurate and fast responding temperature reading you always need good thermal contact between the sensor and what you're measuring. Any kind of air gap would hinder both accuracy and response time. In your case Phill, I'd suspect that you'll have enough heat transfer through the threads to get a pretty good reading, but it wouldn't hurt to fill the gap with heat sink compound (or lacking that some grease) just to make sure.

 

[phillnjack2]

Re: Temp Sender not fitting 100%

heat sink compound !!! thats sounds very good to me.
i was originaly thinking oil or water, but grease sounds a much better answer.

is heat sink compound easily available ? does it go hard or stay soft ?

I too think an air gap would be a bad idea.
The original fitting for the omc engine was probably for their own fitting made longer, stopping people buying after market fittings.
Many things made by omc seem to be of their own very different size to other brands for this very reason.
Now also the overheat alarm sensor does go all the way in and does touch the head with no air gap !!!!!

Im not realy expecting a 100% accurate reading, but as long as i can see for example 70c at normal running temp on average, i
will know if on another day it should go much higher it will be getting too hot etc.

I dont like to disagree with epople on here as they normaly know a lot more about certain stuff than i do.
(especialy the electrical stuff)..

by the way any idea on normal running temp of a 60hp evinrude triple 1995 ?


phill..

 

[metriccrescentwrench]

Re: Temp Sender not fitting 100%

Here's one source for heatsink compound .... McMaster-Carr, part number 3883K24. It will remain a paste-like consistency.

As far as operating temperature, the factory manuals for both of my engines calls for a temperature at idle of about 145 deg F and when running above idle speed it drops down to 125 deg F. I'd guess yours should be similar.

 

[minuteman62-64]

Re: Temp Sender not fitting 100%

I'm no expert, but that looks like the type of sender that is made to sense the cooling water temperature - that would screw into the water jacket.

 

[metriccrescentwrench]

Re: Temp Sender not fitting 100%

I think you're correct, I believe he bought that one because it would fit existing threads.

 

[phillnjack2]

Re: Temp Sender not fitting 100%

quote
I'm no expert, but that looks like the type of sender that is made to sense the cooling water temperature - that would screw into the water jacket. ..........

yes i did buy the type you refer to, its the very same type that was originaly sold by OMC, many outboards have had
these fittings that go into threads in the cylinder heads/water jackets, but not actualy in water.!!!!!!!
I have tried to get an original OMC/BRP fitting, but they dont seem to exist anymore due to the OMC ones being a bit of a failure.
Also these same types are sold by many companies with a z fitting bracket, so the sender touches the metal head.

But being as mine already has a threaded hole that goes directly through the water jacket and onto the cylinder head i thought
it would be the best place to fit it.
Being threaded in there is no chance of accidentaly knocking it or vibration stopping the contact, its also at the top right hand
side of cylinder head in a very unobtrusive place.
I just wanted to find out whats the best way to do this due to the sender not being long enough to touch the head.

Now i have had answers from above, it will be a very simple easy fitment that should work perfect for me.
The guage i have got is a DURITE guage, from 40c to 120 c (104f - 248 f) with 80 right in the midle.
in the uk and europe temps are we mainly in celcius nowdays, so this will also be good for me.
I hope to see around 50c - 65 c on the guage during normal use...if it goes up at any time then i know ive got a problem.
The overheat alarm seems to be at a temperature that i would consider way to hot for safety.
I will be running independant wiring for the guage and not interfeering with the tan set up already in use by the alarm etc.

Before fitting to boat its going in a cup of very hot water to check its working ok, just incase ive got a duff one.
I have bought brand new guages before that had to go back due to being a non working item, it can happen !!!!!


phill............

 

[minuteman62-64]

Re: Temp Sender not fitting 100%

Ah. OK. Those sensors can be used either in contact with the cooling water flow or in contact with the cylinder head. I didn't know that.

So, if the NPT threaded hole in your water jacket was open, and the motor was running, there would be no water coming out of the hole? If that's the case it looks like some of the suggestions above would work.

How about this? Do a trial installation. Get one of those "point and shoot" temperature guns ad HF or similar and sue it to check the head temperature with the gauge reading.

 

[glenn property of pam]

Re: Temp Sender not fitting 100%

any place that does computers should have the heat transfer paste in a small tube as you wont need much

 

[phillnjack2]

Re: Temp Sender not fitting 100%

cheers Glenn, ill go to pc shop tommorow.
will fit the guage and sender then, as tested it today with different temps on a metal base and its pretty accurate.

Was dissapointed though when i looked in a cupboard tonight and found a brand new temp guage i bought about
10 years ago sitting in its box untouched !!!!!!!!!!!!!

still atleast ill have a spare if i do manage to break or destroy this one i suppose.


phill.