I would like to add audible oil pressure and temperature alarms

San_Diego_SeaRay

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Hello!

Well I purchased a major project: 1982 27' SeaRay Sundancer w. twin Mercruiser 5.7s. Gonna take a lot of work to get these overhauled but I'm well on my way and everything is going great so far.

One thing I'm going to insist on is installing audible oil pressure and temperature alarms. I see that Cole Hersee makes exactly what I'm looking for, but I have some questions I was hoping someone can help me with:
  • I imagine this is the way it operates: The body of each switch is grounded to the engine, when a certain value is reached (too hot or not enough pressure) the circuit is completed and the buzzer sounds? So the buzzer is fed a “hot” wire and grounds out when one of the switches gets tripped? Is this correct?
  • Are there already made locations on a Mercruiser 5.7 where the switches can be screwed in to? If so, do you know where they are? Are the threads universal or do I have to buy the Cole Hersee Chevy version?
  • Are there any other brands that make something similar? If so, which one would you prefer and why?

Thanks in Advance ;) -

JC
 
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UncleWillie

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How it works... The Alarm is supplied a Hot wire to one side and the other side floats (silently) until one of the sensors provide the ground to complete the circuit.
Not sure if this is what you meant, ("Grounds Out" is a nebulous term)

It would surprise me that the Merc 5.7 didn't have the sensors in the first place.
Did someone remove them, or are they present and just not wired.
The Temp switch is usually on the thermostat housing, and the Oil switch is a little lower down on the block.
 

alldodge

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Hello!

Well I purchased a major project: 1982 27' SeaRay Sundancer w. twin Mercruiser 5.7s. Gonna take a lot of work to get these overhauled but I'm well on my way and everything is going great so far.

One thing I'm going to insist on is installing audible oil pressure and temperature alarms. I see that Cole Hersee makes exactly what I'm looking for, but I have some questions I was hoping someone can help me with:
  • I imagine this is the way it operates: The body of each switch is grounded to the engine, when a certain value is reached (too hot or not enough pressure) the circuit is completed and the buzzer sounds? So the buzzer is fed a “hot” wire and grounds out when one of the switches gets tripped? Is this correct?
  • Are there already made locations on a Mercruiser 5.7 where the switches can be screwed in to? If so, do you know where they are? Are the threads universal or do I have to buy the Cole Hersee Chevy version?
  • Are there any other brands that make something similar? If so, which one would you prefer and why?


Thanks in Advance ;) -

JC

The two senders are actually switches, one Normally Open (NO) and one Normally Closed (NC). The NC oil pressure switch remains closed until oil pressure exceeds 2 to 6 PSI. The NO water temp switch remains open until temp exceed 200 degrees F.

Power comes from your key ignition source (purple wire) to the buzzer. From the other sides of the buzzer it goes to both switch's. To install the oil pressure switch look below the distributer and find the oil pressure sending unit for the gauge. Remove the gauge sender, add a Tee fitting and install the switch with the sender.

Look on the thermostat housing for a plug which can be removed. You should have your temp gauge sender on one side. Remove the plug and install switch. If you do not have an additional plug, do not Tee with the gauge sender. need to find another location on the block. Provide your engine serial number and we can see if there is another spot.
 

San_Diego_SeaRay

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Uncle Willie and AllDodge –

Thanks for the replies. That helps a lot. These 5.7s may very well have had these switches installed originally. But when I bought the boat, the engines could be described as “stripped lumps of rusted iron”. They didn’t have hoses, belts, carbs, alternators, thermostat housings and a lot of other things. Fortunately the internals were in great condition. So I guess you can say I’m really starting from scratch here.

Since they didn’t have thermostat housings, I went out and bought an aftermarket one. Looking at it, I can indeed see two plugs that can be removed and look the same size. I’ve attached a picture that points out the locations. Is there a location that’s better than the other?

The engine serial number is 6072521 – MCM 260 manufactured in 1981.
 

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alldodge

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Uncle Willie and AllDodge –

Thanks for the replies. That helps a lot. These 5.7s may very well have had these switches installed originally. But when I bought the boat, the engines could be described as “stripped lumps of rusted iron”. They didn’t have hoses, belts, carbs, alternators, thermostat housings and a lot of other things. Fortunately the internals were in great condition. So I guess you can say I’m really starting from scratch here.

Since they didn’t have thermostat housings, I went out and bought an aftermarket one. Looking at it, I can indeed see two plugs that can be removed and look the same size. I’ve attached a picture that points out the locations. Is there a location that’s better than the other?

The engine serial number is 6072521 – MCM 260 manufactured in 1981.

They should work.
Since your engine was stripped, have a look at this thread to see what this guy is doing. He is changing from that style thermostat to the newer one.
http://forums.iboats.com/forum/engi...nes-outdrives/9252596-thermostat-housing-swap
 

San_Diego_SeaRay

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They should work.
Since your engine was stripped, have a look at this thread to see what this guy is doing. He is changing from that style thermostat to the newer one.
http://forums.iboats.com/forum/engi...nes-outdrives/9252596-thermostat-housing-swap


Ha. I've been pulling my hair out about this very issue the last couple of days. When I started this project last November, I bought Mercruiser Tech Manual 3. In that manual, they mention model MCM260, which is the model my engines have written on them on their information tags on the valve covers. And when I called Mercruiser support they confirmed this is my model. So I look in the tech manual, and I see that the MCM260 has log style manifolds. But then there's another model called the MCM260R in the manual that nobody seems to know anything about. It has center rise manifolds. I'm scratching my head because my engines came w. center rise manifolds. I called Mercruiser back and asked them what the difference between the MCM260 and the MCM260R is; they said they didn't know. I said "Could it be that Mercruiser was getting away from log style manifolds around this time and they decided to designate later model MCM260s w. center rise manifolds with an R to differentiate these engines?". The person in support said "Yeah, that sounds possible". ....Sigh :facepalm:. Everybody knows what an MCM260 is, but I can't get any traction on a what a MCM260R is.

Anyway, I figure whoever owned this boat before me at some point decided to do the conversion to center rise manifolds. Unfortunately I don't have all of the parts of the puzzle to work with. Appreciate pointing out that other thread. I'll have a deep look at it later. I might have purchased the wrong T housing but I'll have to do some research; seems like that thread would address this very subject.
 

alldodge

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If you can get away from the log style I would

Edit: when looking up the 260R it also shows up with 898R and 288R for exhaust. All exhaust manufactures identify them as center risers manifolds.
 
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San_Diego_SeaRay

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If you can get away from the log style I would

Definitely will. I already have the center rise manifolds; they came with (not originally though...purchased by the previous owner and installed at some point before I bought the boat). Question for me is why did Mercruiser get away from the "warm" manifolds and move to the "cold" manifolds. I purchased a T housing that supports "warm" manifolds.

I haven't mentioned this, but I also bought a fully complete 1983 MCM260 on Craigslist in great shape (apparently it was a remanufactured engine originally purchased from Michigan Motorz). I'm using it as a "template" from which to rebuild one of my original MCM260s. I'm actually only rebuilding one of the original 5.7s and will use the Craigslist engine as the second engine. I've uploaded some pictures of both the Craigslist engine and one of my original 5.7s. The Craigslist engine has a mid-80s "warm" cooling configuration. I bought my new thermostat housing based on what was on this Craigslist engine.

Edit: when looking up the 260R it also shows up with 898R and 288R for exhaust. All exhaust manufactures identify them as center risers manifolds.

Yeah so to me it seems that this is evidence Mercruiser used this as a designation to distinguish the migration away from log style manifolds. However, when you look through the Tech Manual, almost every subject (not just cooling and exhaust) makes a distinction between MCM260 and MCM260R. You would think these are two completely different beasts.
 

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Fun Times

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So I look in the tech manual, and I see that the MCM260 has log style manifolds. But then there's another model called the MCM260R in the manual that nobody seems to know anything about. It has center rise manifolds. I'm scratching my head because my engines came w. center rise manifolds. I called Mercruiser back and asked them what the difference between the MCM260 and the MCM260R is; they said they didn't know. I said "Could it be that Mercruiser was getting away from log style manifolds around this time and they decided to designate later model MCM260s w. center rise manifolds with an R to differentiate these engines?". The person in support said "Yeah, that sounds possible". Everybody knows what an MCM260 is, but I can't get any traction on a what a MCM260R is.
Hi there, I found some homework for you if interested.:)

First just to be sure, have a look at this bulletin to see if you can ID your exact engine model. Stern drive or inboard.. See pages 1, 3 & 6. http://www.boatfix.com/merc/Bullet/95/95_05.pdf

Below are some things that you might need to take into consideration about the model designation revision that took place around 1983. There doesn't seem to be a whole lot mentioned about the changes that affected the engine external components or the rear engine mounting location. The info found mostly covers the stern drive and transom assembly.

As you read the history quote below, Keep in mind the the exhaust went from log to center risers which may also change the Y pipe to elbow size and connection angle. https://www.perfprotech.com/blog/articles/mercruiser-3-4-exhaust

Histroy of the Mercruiser Alpha Sterndrive Beginning in 1983 Mercruiser introduced the R/MR/Alpha 1 series of sterndrive models. These units differed greatly from previous years not only in design but also in that the flywheel housing on the engine changed at this point. This creates one of the big break points customers should be familiar with when inquiring about re-powering older boats. Since the flywheel housing changed from 1982 to 1983, you cannot couple a new engine to a pre-1983 sterndrive unit as the rear engine mount spacing differs on the new engine and therefore will not match to the old style inner transom plate. The other difficulty is that the newer 14 inch flywheel utilize a larger coupler that prevents re-using the old flywheel housing on the new engine.
https://www.perfprotech.com/blog/art...a2-sterndrives

http://www.boatfix.com/merc/Bullet/83/83_23.pdf
http://www.boatfix.com/merc/Bullet/84/84_18.pdf
Pages 15 - 21, http://boatinfo.no/lib/mercruiser/manuals/mercruiser3.html#/14
http://forums.iboats.com/forum/engi...rives/548694-what-is-different-about-mcm-470r

http://www.mercruiserparts.com/selectSerailRange.asp?doc_nbr=260+(4+BBL.)++++GM+350+V-8+1978-1982
http://www.mercruiserparts.com/selectSerailRange.asp?doc_nbr=260+(4+BBL.)++GM+305+V-8+1982-1986
 

UncleWillie

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.... Looking at it, I can indeed see two plugs that can be removed and look the same size. I've attached a picture that points out the locations. Is there a location that's better than the other? ...

Let me mention this based on a modern T-Stat housing and may or may not apply to your housing....
On some housings there are two water paths internally.
One Path will have the constant water flow that circulates through the engine.
The other path is the back side of the thermostat and only has water flow when the T-Stat opens and is dumping water to hold temperature.
Will it make a difference which water you monitor? Maybe not! The housing should be the same temperature as the block.
However, the T-Stat flow might produce delay in alarming if the engine overheats because the T-Stat failed and the Sensor is monitoring an air bubble instead of the overheated circulating water.

I can't tell from the picture if the two ports are going to be on the same side of the T-Stat or one on each side.
I would favor the port that is in the circulating water, over the T-Stat dump water if at all possible.
 

San_Diego_SeaRay

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Let me mention this based on a modern T-Stat housing and may or may not apply to your housing....
On some housings there are two water paths internally.
One Path will have the constant water flow that circulates through the engine.
The other path is the back side of the thermostat and only has water flow when the T-Stat opens and is dumping water to hold temperature.
Will it make a difference which water you monitor? Maybe not! The housing should be the same temperature as the block.
However, the T-Stat flow might produce delay in alarming if the engine overheats because the T-Stat failed and the Sensor is monitoring an air bubble instead of the overheated circulating water.

I can't tell from the picture if the two ports are going to be on the same side of the T-Stat or one on each side.
I would favor the port that is in the circulating water, over the T-Stat dump water if at all possible.

I see what you're saying. I guess it would matter *if* the thermostat failed to open, and the water never circulated past the sensor. In that case, you would insist on having the sensor tapped into the "constant water flow that circulates through the engine", right? But in my T stat housing, both of those plugs are accessing the same part of the housing just below the thermostat (based on this exploded view). So they are on the "engine" side, and *should* be triggered if the t stat never opened....hopefully.

This is the way my t housing seems to work: When the engine is cold and the water is below 140 degrees, 100% of the new raw sea water is funneled past the ball check valves and directly to the exhaust elbows for immediate release w/o any cooling functions. As the engine side water starts to warm, the thermostat opens and *some* of the warm water is cycled back into the engine right in front of the circulation pump. The hot water that is not recirculated back into the engine is circulated up through the top of the t stat housing and then to the bottom of the exhaust manifolds, where it moves up through the manifold ports to cool them.

Meanwhile, at the very point where the some of the hot water was diverted back to the engine , *some* of the new raw sea water that was originally being 100% dumped into the elbows now gets diverted and merged w. this hot water and re-introduced to the engine.

So I think based on your comments, don't put the sensor on the side where the "cold water meets the hot water after the thermostat has opened". But from looking at my housing, it seems I couldn't even do this if I wanted to. Both plug are on the same "hot" engine side. So that begs the question why? Which we can probably only guess at.
 
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alldodge

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In your picture the one which has the blue arrow on it will be on the engine side. This is the side which will give you a good reading for engine heat. The red arrow is for water leaving going to manifolds
fetch

This link has the cooling system diagram for the housing you purchased, page 7A-43 or 890
http://boatinfo.no/lib/mercruiser/manuals/mercruiser3.html#/888
 

UncleWillie

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...So I think based on your comments, don't put the sensor on the side where the "cold water meets the hot water after the thermostat has opened". But from looking at my housing, it seems I couldn't even do this if I wanted to. Both plug are on the same "hot" engine side. So that begs the question why? Which we can probably only guess at.

Be sure you understand the how the water flows!
Again based on a current Merc block and not necessarily your block....

The Cold water passes through a "Y" connection external from the block.
Most of the water bypasses the block and heads straight to the exhaust headers.
The remainder of the flow initially fills the block and is circulated by the water pump.
Once the block reaches temperature, the T-Stat opens to dump HOT water to the exhaust.
This allows more Cold water to enter the bottom of the block to maintain temperature.

It would be more accurate to thinks of the thermostat as a device that opens to allow hot water OUT instead of allowing Cold water IN.
If the thermostat were metering the cold water entering the block, It would immediately close as soon as it opened.
If placed in the exit flow of the block, it will not close again until the block had cooled to the desired temperature.

Look closely at how the thermostat housing meters water when all the parts are assembled.
There is more engineering in that simple casting than meets the eye.
 
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