Detroit 671 non T water temp

[Mario Tranquilein]

I finally start my engines after 9 years!, the gauge marks 185 in iddle. I read that 185 is the max but my concern is what would happen under load? How many termostat have my engine and please where are located?. Can a eliminate them? My Hatt live in Caribbean warm waters. I know some motors needs the Termostat for create water preassure in the sistem. But i really preffers run my engine at cold and practical possible. Please any suggest? Thanks

 

[yachtsmanbill]

I think an N at 185 is ok as long as it doesnt creep up under load. My 12-71Ns run at 185 which the engine actually needs to prevent a bunch of other problems. Dont remove them. Turbo Detroits are a whole different issue... ws

 

[q240z]

My 671Ns run pretty much locked onto 165, and raw water temps up here run into the mid-80s in summer. 185's hot if you ask me.

Mario, I recommend getting a Detroit manual. Thermostats could be the issue. You could also have clogged heat exchangers. The intake hoses could be collapsed on the inside. I think I read where you just replaced the impellers, but the ones you put on were different than the ones you removed. Are you moving lots of water out the exhaust?

What I absolutely would not do is remove the thermostats. That's a hack "repair" that you will almost certainly regret eventually.

 

[Mario Tranquilein]

Thanks to everyone: I have the Detroit manual I will check how remove the head exchanger core. About the termostat I could not identified where are located I want to start with that, then heat exch. The impellers are pumping and incredible amount of water and I touch it and feels cold a thing that surprise me. Where can I order cold termostats I will like 165 because is better to have margin in a emergency. If there any idea where is the core of the HE and the termostats if there are one or two for each motor. thanks a lot to both. Mario H43DC

 

[lumina]

Hi All,

I have 8V71 naturals, at idle sitting at the dock they run at 180 and under load say 1800 RPM they rarely exceed 185.

FYI both raw water cooling systems have been dismantled and flushed within the last 2 years.

 

[Boatsb]

Thanks to everyone: I have the Detroit manual I will check how remove the head exchanger core. About the termostat I could not identified where are located I want to start with that, then heat exch. The impellers are pumping and incredible amount of water and I touch it and feels cold a thing that surprise me. Where can I order cold termostats I will like 165 because is better to have margin in a emergency. If there any idea where is the core of the HE and the termostats if there are one or two for each motor. thanks a lot to both. Mario H43DC

How are you measuring the temps and where. Forget the gauges for a minute and get a laser thermometer. The first thing you need to do is determine if the readings are accurate.

 

[yachtsmanbill]

I think the V71s run a tad warmer. I shot mine at about 10 different locations and they all came in between 179 and 187... I would guess that the 185 on the gage is pretty close. It reads on the water manifold (return) from the heads to the HE.
FWIW... the 12-71s have 4 thermostats... two on each bank. ws

 

[Will]

185 seems very hot for a 6-71 at idle. On inline 6-71's, the thermostat is often on the back end of the fresh water manifold which sits on the head between the valve cover and above the exhaust manifold. It usually has a water tempurature sender and/or an over-tempurature sensor with electric wires attached somewhere.
Will

 

[yachtsmanbill]

Maybe I should clarify the 12-71 part... if I start them cold and idle all day they will reach 130-140. If I run them at 1500 for 15 minutes they will reach 170 and underway run all day at 180-185 depending on load. ws

senders are the last stop before the T stats on the return on the water manifold.

 

[Mario Tranquilein]

Thanks for clarify thay 671 only have one termostat and yes my have a sender close to the termostat cover. Yesterday in just seconds reach 200 and I stop them in the moment. But the motor feels only warm at the HE no hot noises or boiling water. So I start to suspect about my readings I probably will change to mechanical gauges that never fails. I bought the repair kit for the HE if I take the water refill cap the water looks full of mud and 95% I thinks that's the problem. If the mud cover the sender probably reads incorrectly. Where can I buy 160 termostats? I ask in a Detroit dealer here and they only have 170 I preffer to have more margin just in case of broken hose etc. Thanks again!

 

[Mario Tranquilein]

Hi again! For remove the HE core can I only remove the left side of the HE or ai need to remove the side that have the o rings etc. I have a friend that fills the HE with acid and he claims that works great without remove them but I don't feels that's a good fix

 

[q240z]

I have run muriatic through mine without removing the HE core and had good results.

Have you tested the actual temperature with an infrared thermometer?

 

[Mario Tranquilein]

[QHi: no I din't yet, where you put the acid in the fresh water area or both??? And in the raw water area how you filled with acid? Before the water pump or just disconnect both sides and lived the acid for a while? Please let me know, I already bought the repair kit but the screws looks rusty and I'am afraid to break one during the dissambly. In the fresh water area I have a lot of mud so I imagine the raw core probably is full of mud and sea coral too. Thanks. MarioUOTE=q240z;169008]I have run muriatic through mine without removing the HE core and had good results.

Have you tested the actual temperature with an infrared thermometer?[/QUOTE]

 

[q240z]

I only did muriatic on the raw water side. If you've got "mud" on the freshwater side, I'd begin by flushing it clean. I would imagine a dilute muriatic flush might be good on the fresh side, too, though I've never done it.

When I did my HEs, I began with a bucket of diluted muriatic. I used a hose and Shurflo water pump and pushed the muriatic through another hose that was connected to the HE inlet (of course, you first disconnect the HE from the raw water system). From the HE outlet, I connected another hose that went back to the bucket. Turned on the switch and watched things bubble for about 5-10 minutes. Then put the inlet hose into a bucket of clean water with a dash of baking soda in it and ran the pump for 2-3 minutes. Hooked up the HE and VROOM!

 

[newinlet]

671N. is a 173F thermostat

 

[JD5652]

671N. is a 173F thermostat

Winner! Winner! Chicken Dinner!

You should be able to shoot right on the thermostat with an infrared heat gun.

If you haven't started these engines in 9 years, I'd HIGHLY recommend you remove the heat exchanger bundle and clean with diluted muriatic acid.

BEFORE, you do that, Use the Pencool system to flush out the freshwater side of the engine block. It's also an acid-based system that requires you to drain and fill the fresh water cooling system several times.

After all that, you should be good to go even in warn caribbean waters.

IF the REAL temps are 185 at the slip with an unloaded engine, you have cooling issues. The thermostats should open at about 173.

 

[Captain Ralph]

671N. is a 173F thermostat

Winner! Winner! Chicken Dinner!

.

I wonder if you kids know it was a 13 year old thread your responding to?

 

[whoover]

Maybe now the engines have not been started in 22 years?

Walt Hoover