200f

[sprague]

I have an A4 that I installed in a Hullmaster Douglas. Originally it came with a Farrymann Diesel but it was very underpowered. I replaced the diesel with the A4 and it seems to be doing the job. I installed a capillary type temperature guage. It takes a few minute to warm up an operates at 200F. As a former auto mechanic this did not bother me until I started reading articles about the A4s running at temperatures as low as 140F and as high as 180F I am not having any trouble with the engine but am concerned about the temperature. Any comments?

[Dave Neptune]

Temps

sprague, if you are running with raw salt water cooling it is to high. If you are using a heat esxchanger some on this site wil be a bit envious of such a temp. What thermostat set-up are you using?
Myself I run at 140 on salt water with no thermostat and have done so for 26+ years.
If your temp is steady you might re-check the temp after a run by turning on the key and checking the engine temp about 10 minutes after shut down. This will give you a good idea of the actual temp the core of the engine is running at.

Dave Neptune

[Dave Neptune]

OOps

Just noticed that was your first post, welcome to our forum.

Dave Neptune

[Mo]

Welcome aboard.

I'm with Dave. No thermostat, however, I do have a ball valve in the line just before the thermostat housing. Mine is salt water cooled and I keep the ball valve opened to 45 degrees (1/2 open). Never above 140.

I use the hotter operating plugs which cut down on the carbon in the combustion chambers and my plugs are clean as is everything else in there.

I also do a muriatic acid flush every 3 or 4 years....easy to do.

[sprague]

sprague, if you are running with raw salt water cooling it is to high. If you are using a heat esxchanger some on this site wil be a bit envious of such a temp. What thermostat set-up are you using?
Myself I run at 140 on salt water with no thermostat and have done so for 26+ years.
If your temp is steady you might re-check the temp after a run by turning on the key and checking the engine temp about 10 minutes after shut down. This will give you a good idea of the actual temp the core of the engine is running at.

Dave Neptune

I have checked the system as you suggested but it just cools slowly after use as you would expect. It has a thermostat and there is good water flow through the exhaust. The electric temperature sensor read the same. I recently did a 20 hour trip across the lake and the guage remained steady at 200F. I have ordered another thermostat and will see if that makes a difference. As I said before I am used to engines running at 200F and it seems to get great fuel economy

[sprague]

Just noticed that was your first post, welcome to our forum.

Dave Neptune

Thank you...much appreciated.

[sprague]

I'm with Dave. No thermostat, however, I do have a ball valve in the line just before the thermostat housing. Mine is salt water cooled and I keep the ball valve opened to 45 degrees (1/2 open). Never above 140.

I use the hotter operating plugs which cut down on the carbon in the combustion chambers and my plugs are clean as is everything else in there.

I also do a muriatic acid flush every 3 or 4 years....easy to do.

My question is this: At 140F is the water absorbing enough of the heat generated by the engine? When the water passes through the engine too quickly, it will not have time to absorb the heat. Therefore the water may be cooler but engine may actually be running hotter.

[J W Greenstone]

The water may be passing thru more quickly, but isn't it is also being replaced more quickly by much cooler intake water? I would think the heat transfer would be about the same, if not perhaps more.

John G.

[hanleyclifford]

The water may be passing thru more quickly, but isn't it is also being replaced more quickly by much cooler intake water? I would think the heat transfer would be about the same, if not perhaps more.

John G.

On a raw water cooled engine running without a thermostat permits much greater and faster flow thru the system thus keeping it cleaner. A thermostat is a huge obstruction in a small engine cooling system. If I ever went to raw water cooling I'd get rid of mine in a heartbeat.

[Dave Neptune]

Temps

sprague, the 200 degree is a very good temp to operate an engine at for economy, clean burning and wear on rotating parts. However it is not good for salt water as the salts can begin to deposit at around the 170 degree mark or so. I'm really not sure but that is the reson most saltwater cooled engines use a 140 ~ 160 degree t'stat.
I too keep my engine at 140 without a t'stat with a valve in the bypass line and it sits at around a 45 degree angle. When I begin to need to close the valve down to maintain my 140 I know a flush or debree inspection is in my near future. I have run this engine like this fo 26+ years with no problems and 2 acid flushes. During that time I have cleaned out the exit fitting area on the manifold every few years or so.
By using the bypass you are not restricting the flow of water you are splitting the flow to maintain the temp manually (the valve) not automatically as with the t'stat. It's simple and adjustable not so with the t'stat.

Dave Neptune

[lat 64]

The water may be passing thru more quickly, but isn't it is also being replaced more quickly by much cooler intake water? I would think the heat transfer would be about the same, if not perhaps more.

John G.

If the water is moving through the block fast it will remove more heat. This is because the temperature differential is greater. This is called Delta—T. Heat always moves from hot to cold in conduction, and the cooler the water, the faster the cooling. What does not happen is that the water gets up to temperature because it is replaced with cold water quickly. If you slow down the flow the water will get hotter, but the Delta—T will be less and the heat transfer will be less. This is Ok for guys like me that like to use the heat for cabin heater etc. Not so good for the Florida crowd.
Cooling systems are a balance between keeping the engine up to good temp for efficiency and stuff, and cool enough for not burning up the motor. thus the bypass valve was concived.

I like 160 to 180 myself for the a-4. It just seems happier, but I'm sure at these temperatures, these old motors would never make EPA approval for emissions.


Welcome,
Russ
P.S. Full disclosure; I run with antifreeze and a heat exchanger—I don't need to worry about the salt deposits.

[sprague]

sprague, the 200 degree is a very good temp to operate an engine at for economy, clean burning and wear on rotating parts. However it is not good for salt water as the salts can begin to deposit at around the 170 degree mark or so. I'm really not sure but that is the reson most saltwater cooled engines use a 140 ~ 160 degree t'stat.
I too keep my engine at 140 without a t'stat with a valve in the bypass line and it sits at around a 45 degree angle. When I begin to need to close the valve down to maintain my 140 I know a flush or debree inspection is in my near future. I have run this engine like this fo 26+ years with no problems and 2 acid flushes. During that time I have cleaned out the exit fitting area on the manifold every few years or so.
By using the bypass you are not restricting the flow of water you are splitting the flow to maintain the temp manually (the valve) not automatically as with the t'stat. It's simple and adjustable not so with the t'stat.

Dave Neptune

One difference is that I am not in a salt water environment. Eventually I will be taking her south however. I may try it with the thermostat just to see.
ar

[Mo]

If you install a by-pass valve and remove the T-stat you will be ahead of the game. I've had mine removed for 4 years....never had an overheating problem; never had to replace the head gasket.

That keeps the engine dependable. I can hold my fingers on the block and head while she is running. If I get into a sea state and have to use cut loose a few more horses she will not overheat.

My carb is leaned out and the hotter plugs...you will be delighted at how well it runs....on and on and on. Not bad for an old design. Just a note and certainly not intended to snub other members' point of view....keep it cool and keep the restrictions to a minimum. I haven't had to help with an overheating problem on an engine that had the T-stat removed and a by-valve in place.

[J W Greenstone]

Does this bypass valve get installed right before the thermostat housing, between the "T" fitting on the side of the engine and the thermo housing? What kind of valve is best?

John G.

[Mo]

Just before the T-Stat

Yes, install just before the T-Stat. There's a pic of one in my "engine album". When I rigged mine I didn't know about MMI. I got plumbing material at the local hardware store and pieced it together. That said, Moyer sells a by-valve kit with everything you need.

PS: The valve is fully opened in the picture because it was taken when she was on the hard and it was open to winterize with antifreeze...made sure it went everywhere.