Which to use water pressure or temp guage on 1987 225 Evinrude outboard

[j_k_bisson]

Which is the better guage to use for this type of motor?

I am rebuilding a Evinrude 225hp outboard. I was told by the dealer that seeing I was reworking (modifying) the cooling system to the 70hp thremostat and spring system that the engine will be prone to over heat unless the thermostat springs are heated and played with untill they "lift" at the proper temps and RPMs. Anyone else ever hear this?

So this leads me to ask the question. On outboards which is better water pressure or temp guage? I'm trying to not have to put both in my boat.

 

[wilde1j]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

I have both on my boat. The pressure gauge will give an early warning of pump wear or suction side blockage. Water pressure, like the tell tale, are no guarantee cooling is taking place properly. The temp gauge will alert to malfunctioning thermostats or other persistant temp issues. All my boats in the last 25 years had both. Contiluing to run an overheated motor is a prime cause of PH failure, along with lean running as another.

 

[bob johnson]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

if EITHER one OR the other...you gotta go with the temp gauge......everything is to make sure the motor dont overheat... the temp guage lets you know... you can turn the motor off and save it...

the others( tell tale, water pressure,) can show good numbers and you could still over heat....and ruin your motor!!

but why not use BOTH!!

i ahve a temperature guage for EACH head!!

bob

 

[j_k_bisson]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

if EITHER one OR the other...you gotta go with the temp gauge......everything is to make sure the motor dont overheat... the temp guage lets you know... you can turn the motor off and save it...

the others( tell tale, water pressure,) can show good numbers and you could still over heat....and ruin your motor!!

but why not use BOTH!!

i ahve a temperature guage for EACH head!!

bob

Each power head (Twins) or each side of power head? (V-6 one on one side and one on the other?)

I can see where the temp guage is more important. It is telling what temp the water is at.

Next question:

Where to pipe it in at. The top of the block or bottom? Seeing the water cascades down the cylinders. Right?

 

[bob johnson]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

Each power head (Twins) or each side of power head? (V-6 one on one side and one on the other?)

I can see where the temp guage is more important. It is telling what temp the water is at.

Next question:

Where to pipe it in at. The top of the block or bottom? Seeing the water cascades down the cylinders. Right?

well NORMALLY temp guages dont measure the water temperature ITSELF, they measure the temperature of the metal of the head.. and as such they are bolted or screwed into some part of the head, usually close to the center, to measure the average temperature of the head...ie, one cylinder maybe running hotter than its sister cylinder...

so calling the temperature guage a WATER TEMP GAGE is a misnomer, Id say.

on motors that dont have a pipe fitting recepticle to screw the SENDER into they attach under a head bolt someplace..

good luck

get the whole package as a kit to make sure the sender and the gauge are in sync..

good luck

bob

 

[wilde1j]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

Like this:

 

[Silvertip]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

well NORMALLY temp guages dont measure the water temperature ITSELF, they measure the temperature of the metal of the head.. and as such they are bolted or screwed into some part of the head, usually close to the center, to measure the average temperature of the head...ie, one cylinder maybe running hotter than its sister cylinder...

so calling the temperature guage a WATER TEMP GAGE is a misnomer, Id say.

on motors that dont have a pipe fitting recepticle to screw the SENDER into they attach under a head bolt someplace..

good luck

get the whole package as a kit to make sure the sender and the gauge are in sync..

good luck

bob

This is not entirely true. If there is a port that enters the water jacket so water is in contact with the sender, then you indeed have a water temp gauge. If the sender is mounted in contact with the cylinder head using either a "Z" bracket or recessed in a pocket in the head, you technically have a "cylinder head" temp gauge. Regardless, both methods use the same resistance range senders which may look like either the threaded type or the contact (bolt on) type in the following diagram. If you install a sender on each head you can use a single gauge and a toggle switch to toggle from one sender to the other.

Here is a contact (bolt on style sender)

Here is a threaded sender installed directly into the water jacket on a Merc. They can also be used with a "Z" bracket and used as a contact type.

Here is how that is done:

 

[j_k_bisson]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

I found the matching Faria square face gage on ebay to match all my other gages on my dash. The gage is new so even better. So we are going with water temp.

I called Faria and they gave me sending unit number 90401 which is a 1/8 npt sumbmersion sending unit to match the gage. So I'll keep the omc temp sending units in the head for the warning over heat horn. Then either pipe this new unit in the pee hole with a tee fitting or one of the lower 1/8npt openings in the housing where the old cooling system hoses used to hook up.

I understand that need to keep the pee hole at the top to help with air entrapment at the top of the block, but does the sending unit need to be at the top of the block? Right now I can drill anywhere and locate this unit anywhere I want. I have not scrubbed the block after honing yet.

Is there a hotter side on these v-6 looper blocks? Port or starboard? Also the cooling system is a flood system from top down right?

 

[j_k_bisson]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

As I was driving home tonight (just got home) I was thinking about this proposed system. I like the idea of being able to tell how the power head is running. It would help alot in the diagnosis of problems. Sort of like Rotax aircraft motors. Remember the airboat I designed and helped make? They have temp sensors on the cooling water and exhaust for each cylinder. Anyways, is there sending units (non submersion) that fit 1990 evinrude 225hp heads? I know the threads in the heads are for plastic retaining nuts and are not a universal thread. Or will the OMC temp sensors work with the Faria gage? I know the Faria guage is 100'F-250'F and is 240ohms if that helps. ANyone know how the temp sencors from OMC work. I have a brand new set of temp sensors for the motor. Would be a shame to have to post them on ebay to get rid of them because I did not use them, but hey the things on a motor the less that can go wrong. I hate rodundant systems. Just adds weight.

 

[bob johnson]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

As I was driving home tonight (just got home) I was thinking about this proposed system. I like the idea of being able to tell how the power head is running. It would help alot in the diagnosis of problems. Sort of like Rotax aircraft motors. Remember the airboat I designed and helped make? They have temp sensors on the cooling water and exhaust for each cylinder. Anyways, is there sending units (non submersion) that fit 1990 evinrude 225hp heads? I know the threads in the heads are for plastic retaining nuts and are not a universal thread. Or will the OMC temp sensors work with the Faria gage? I know the Faria guage is 100'F-250'F and is 240ohms if that helps. ANyone know how the temp sencors from OMC work. I have a brand new set of temp sensors for the motor. Would be a shame to have to post them on ebay to get rid of them because I did not use them, but hey the things on a motor the less that can go wrong. I hate rodundant systems. Just adds weight.

OK lets be CLEAR..

do YOU have temp SENDERS...or
Temp SENSORS for your motor??

they are NOT the same...

the SENSORS are part of the warning syatem... and cannot be hooked to a guage...

SENDERS are what we are talking about to READ the actualy temperature on a gauge!!

and they do NOT go into the same place...you need to keep the SENSORS you have where they are on your motor and hooked up..

if you dont have an open spot on your head made for SENDING units... they you should just go with the style thats bolts under a head bolt , like silvertip posted..

PS: you orginally said you have a 1987 225, then you ask if something fits a 1990 225 head... which do you have??

and SILVERTIP:

i did originally hook up my dual temp senders to a single temp gauge.. and I have NOTHING but trouble.

I had used an on-on switch and it gave me false readings...one would read high, the other would read low...verified by the infared thermometer.

i hooked up an ON-OF-ON switch and it didnt help much...so i eventually went with seperate gauges for each sender... and i get accurate readings now.


bob

 

[boobie]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

I think you should talk to another Dealer. "Heating up thermo springs" Hummmm??

 

[j_k_bisson]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

To clear everything up I have a 1990 225 power head with a 1987 ignition system. And to confuse you even more I have a 1986 mid section and lower unit. LOL It works. So the reason I said I had a 1987 was to identify the electrical system. I do not have "quick start" feature on my motor that I know of. That came out in 1988.

Here is a pic of the heads and the sensors which are direct replacements for what was in there. Matched up the part numbers. Do they really need to be there? My index finger is pointing to the "sensors" (OMC) holes. The pinky finger is pointing to holes that are not used. Are these threaded holes for the other type of "senders" (Faria gage)?



Sorry for all the questions. But I do like learning this stuff.

So the switch thing does not work accurately. Could it be that the switch was giving off a slight restance? Thus affecting your numbers? Then I'll go with the single temp "sender". Any Idea which head I should go with? Port or startborad?

As to sensors. I could drill out the Sender (pinky finger) hole straight thru to the water passage. Or is the temp I want of the metal and not the water. Seeing that the water temp will not relect the true temp until the thermostat opens.

As to "Heating the springs" The old mechanic (around 65 years old) says that they did not have very good luck with the water cooling system rework. They always need to play with heating the springs and adjusting the length so they work correctly. Is there anything to this?

 

[j_k_bisson]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

Just bumping this to the top. Hoping for a couple of answers.......

 

[j_k_bisson]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

Stopped by my local Evinrude dealer on the way home tonight. They gave me part number 172843 which is NLA. Then they gave me 174675 which is the current part number that will fit into the other hole in the head. They also stated the sender goes into the higher of the two heads, due to that one will heat up first if there is a water problem with the cooling system. This sender is matched to their Evinrude gage. Not a Faria.

Anyone try these parts before?

Any chance anyone try these parts with a faria gage?

By chance anyone have the specs on this here part. The ohms for 100'F and 250'F?

 

[Faztbullet]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

I was told by the dealer that seeing I was reworking (modifying) the cooling system to the 70hp thremostat and spring system that the engine will be prone to over heat unless the thermostat springs are heated and played with untill they "lift" at the proper temps and RPMs.

That fellow dont understand the system as this converts engine into 2 seperate systems and t-stats/springs control only that head as there is no crossover plumbing. The 2 tan sensors are for a hot horn and pull the water pressure guage off adapter plate elbow. In my opinion temp guages are a waste of money and problems as I have see customers chase non existent heating problems that guages registered and none I have seen are accurate except on a inboard,,...my $.02

 

[bob johnson]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

To clear everything up I have a 1990 225 power head with a 1987 ignition system. And to confuse you even more I have a 1986 mid section and lower unit. LOL It works. So the reason I said I had a 1987 was to identify the electrical system. I do not have "quick start" feature on my motor that I know of. That came out in 1988.

Here is a pic of the heads and the sensors which are direct replacements for what was in there. Matched up the part numbers. Do they really need to be there? My index finger is pointing to the "sensors" (OMC) holes. The pinky finger is pointing to holes that are not used. Are these threaded holes for the other type of "senders" (Faria gage)?

View attachment 83167

Sorry for all the questions. But I do like learning this stuff.

So the switch thing does not work accurately. Could it be that the switch was giving off a slight restance? Thus affecting your numbers? Then I'll go with the single temp "sender". Any Idea which head I should go with? Port or startborad?

As to sensors. I could drill out the Sender (pinky finger) hole straight thru to the water passage. Or is the temp I want of the metal and not the water. Seeing that the water temp will not relect the true temp until the thermostat opens.

As to "Heating the springs" The old mechanic (around 65 years old) says that they did not have very good luck with the water cooling system rework. They always need to play with heating the springs and adjusting the length so they work correctly. Is there anything to this?

is the hole by your pinky a threaded hole???? as in a 1/8th" pipe thread?

if so thats a good place to put the temp SENDOR. i think you still need the sensors you have that go in the larger hole by your other finger...like fazt says it is for the warning horn..

good luck

bob

 

[Silvertip]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

I think there are still some issues with UNDERSTANDING what a temperature SWITCH/SENSOR is vs what a temperature SENDER is. Temperature switches (also called sensors) do not measure resistance. They are technically switches that are either open (normal temps) or closed (overheat). They CANNOT be connected to a temperature gauge and expect to get a reading. Only temperature SENDERS can do that. So for the alarm function you need to retain the switch/sensors. If you add a gauge then you need to add the SENDER (one on each head if you wish). Then and only then will the single gauge with a switch diagram apply. Lastly, installing the temperature SENDER in the tell tale is NOT going to work. You need to get that sender into the water jacket or in contact with the hottest part of the cylinder head. Use either type of sender I showed. The screw in type needs an open port INTO THE WATER JACKET or you need to use a "Z" bracket to mount the sender in contact with the head. Just follow the instructions that come with the bracket.

 

[j_k_bisson]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

Yep the over heat (Big hole) sensors are going in for the warning horn. The temp sender (variable reistance depending on temp) go in the small hole. The OMC part number for this sender is 174675, 172843.

Anyone have the specs on this sender?

 

[bob johnson]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

Yep the over heat (Big hole) sensors are going in for the warning horn. The temp sender (variable reistance depending on temp) go in the small hole. The OMC part number for this sender is 174675, 172843.

Anyone have the specs on this sender?

specs??

its a 1/8th NPT thread, I am pretty sure, the outer thread for the electrical connection is a 10-32 ....it mates to a lot of different OMC offered temp guages from 1988 to 2006

probably even more than that!! since it is also offered for 79-1987 motors as well..

if you have an OMC gauge, you are all set!!!

other than running the wire all the way!!!!!!! there is no provision for the temp sender wire on the harness that i know of....

at least there wasnt on my motor

good luck

bob

 

[phoenixgold2100]

Re: Which to use water pressure or temp guage on 1987 225 Evinrude outboard

Does anyone know if 174675 - 172843 works with a faria temp gauge? I have already ordered the gauges and haven't ordered the temp senders yet. I think the gauges are standard us 33-240 ohms. Is that what these senders put out? I can't see them being strictly omc guage compatable. I was doing some digging and they say most temp gauges are in US ohms 33-240 Any help would be great.