Modification on engine cooling system?

[caltexflanc]

neurodoc, I hope you sort this out, it is often pretty simple.

Great name for a boat by the way.

 

[McGillicuddy]

In answer to your original question, I don’t think that what you are proposing is at all unreasonable. You have a steel hull vessel that runs at hull speed or less. However installing pipe on the hull does provide another failure point in the system in the event of a grounding. Gulf of Mexico steel shrimp trawlers work at high horsepower-low speed-shallow water while dragging big nets close to shore. Also shallow draft tugs have the same issue. The typical solution for them is to weld inverted C channel beam coolers on the bottom. This has several advantages. They are low profile and therefore low drag. They are strong and not easily damaged. They actually increase the longitudinal hull strength of the vessel. They provide more low weight thus increasing stability. They are pretty thick steel so erosion on the inside of the beams take a long time.
Disadvantages are the hull plating head to have sufficient thickness remaining to support the water flow through the channels. No point having 12 mm thick channel coolers if the bottom thickness remaining that they are attached to is only 5 mm. Also, channel coolers remove the ability to water cool the exhaust. So a dry stack would have to be installed. In my view, this is not a bad thing as it removes underwater through hull penetrations which is always a good thing.

As for calculations on how long the runs will be? The fishermen use seat of the pants calculations. Typically I see two runs of 20-30 feet per 350hp engine. The ends are joined together with a short piece of channel. You might actually have a little too much cooling with this set up but that is easily controlled with an appropriately sized thermostat.

Or you can go with a pre-engineered grid cooler such as Fernstrum as mentioned by others. Advantages/disadvantages are discussed in earlier butI would definitely inset that type of cooler in the hull or provide some type of protection for the softer metals in the cooler. That would be a viable solution if a little more expensive.

Good luck and let us know how you decide to proceed.

 

[Transaxial]

The boat is 40 years old. The first owner passed away. The second is a jerk....

A bit over 2 years ago I bought a 40 year old 40' Palmer FD trawler ex fishing boat that had been redone totally about 20 years ago. I think the older guy that did the rebuild or at least contracted parts of it, did a nice job and I have been happy with most of the boat. It had "slight" heating problems according to the PO. Part of the reason I chose this boat was because it has a dry stack and about 40' of 1 1/4" K grade copper for the keel cooler running close in to the keel, down one side and back up the other. I have spent a lot of time (as much as I can living 900 miles away from the boat) trying to be sure all the existing cooling system is in order. There are lots of good suggestions from some smart guys on this forum that you should check before you start into a new cooling system. I have tried the flush, check gallons per minute flow with an external water pump, new thermostat, no thermostat(which helps a lot but then runs too cold), new water pump, modified water pump, increase the size of the keel cooler piping and fittings to 1 1/2", close all the domestic hot water and bus heater valves, and have hired several different technicians and had HD mechanic friends on board with heat guns and thermal imaging camera to go for a run. It still over heats when you get it just above an idle. So I have bought a Fernstrum custom built keel cooler and am going to install it so I can run a really short and direct 2" pipe and hose loop with under 4 psi of back pressure total for just the engine. The other cooler loop will use the existing copper pipe loop and a second belt driven circ pump. Also to maintain the full 2" flow, even in thermostat bypass mode, I have built an Amot style, full flow three way temperature control unit that I will work nicely into the plumbing. The only way I could get a handle on heat rejection numbers was to build a test bracket for my new water pump and drive it with a 3 HP electric motor at about 2500 rpm. Then I knew it was pumping about 60 US gallons per minute and maintaining 8 psi at the pump while doing it. I neglected to say the single main engine is a 6D14 Mitsubishi NA in line 6 that is rated at either 115 or 126 HP at 2600 rpm. The service manual states some of the specs like water jacket heat rejection at 138,000 btu which seems way low, specially considering that loop also goes through the transmission cooler, the hydraulic cooler and the exhaust manifold cooler. The manual also tells you water pump flow and pressure. Another way to see if you have an undersized system is this. By using fuel burn at a max of 7 gph X 138,000 btu per gallon burned makes close to a million total BTU produced. Rule of thumb is that 1/3 goes to each coolant, exhaust, and rotary energy. So since I am cooling the exhaust manifold (50% of that 1/3 ) and 5-8% from transmission cooling, and a small amount from hydraulic cooling, I am getting close to 500,000 btu to move out. The Walter keel cooler sales guy would not even talk about exhaust heat and the other small loads. His comment was "I have been doing this for 30 years, are you questioning me?" Well yes I am because my boat is overheating!! So maybe many of these boats are running undersized coolers??? Water pump flow at 58 gpm and 8 psi, right on spec. Now I checked the flow charts for 58 gpm and there is no way I can push 58 gpm through all that crooked 1 1/4" plumbing with 8 psi. Bigger pump? No because the max water jacket pressure is 15 psi. So now I know it will not cool at full power. Maybe it was made to just be a trawler at 1/3 hp and 5-7 knots. Another interesting formula is the one to determine gallons per minute of flow to be able to move the heat out with the temperature differential your cooling system can provide. GPM = BTU total heat rejection divided by 500 for water (450 for antifreeze) X Delta T which is the difference in temp leaving the engine and the coolant temp returning to the engine. Sea water temp makes a big difference on Delta T. Our BC water is about 55 - 70 F in summer so quite cool. If I run my numbers, 500,000 btu divided by 500 times Delta T of 20 degrees which seems like a good starting point, I get 50 gpm of flow to get that heat out. This is getting kind of long and murky, but these numbers are what I needed to get a handle on where the problem was. Some of these you can get from your service manual, as long as your engine is actually doing that, you can play with some of these formulas and see if your boat is undersized in the cooling department. I would be happy to help you with some of these concepts if you want. I am not the engineer, just the figure out what works and git er done guy!

 

[Transaxial]

McGillicuddy made a great post while I was doing mine about steel channel keel coolers for your steel hull boat. Could be the answer as long as you don't cause problems on the inside while welding on the outside. Sizing numbers I have heard are 4 hp per square foot of cooler surface in water below 55 F and 3 hp per sq ft for warmer water. BC warm!!

 

[DavidM]

I believe that we and the OP are overthinking this problem. To switch to keel cooling is a big change and significant money.


His current over heating problems could be simple to fix or not, but almost certainly cheaper than adding a keel cooling system. And that keel cooling system might have exactly the same problems, if the current system has a problem on its coolant side. Also he will have to keep the raw water system for exhaust gas cooling or install a dry stack system- more bucks!.


He said he could get the data I asked for early in this thread over the weekend. I hope he does so we can try to diagnose what is going on with his current system.


David

 

[twistedtree]

I believe that we and the OP are overthinking this problem. To switch to keel cooling is a big change and significant money.


His current over heating problems could be simple to fix or not, but almost certainly cheaper than adding a keel cooling system. And that keel cooling system might have exactly the same problems, if the current system has a problem on its coolant side. Also he will have to keep the raw water system for exhaust gas cooling or install a dry stack system- more bucks!.


He said he could get the data I asked for early in this thread over the weekend. I hope he does so we can try to diagnose what is going on with his current system.


David

I totally agree. All the diagnostics need to be done regardless of any possible change in the cooling system type. Diagnose the problem, then come up with the solution.

 

[neurodoc]

McGillicuddy made a great post while I was doing mine about steel channel keel coolers for your steel hull boat. Could be the answer as long as you don't cause problems on the inside while welding on the outside. Sizing numbers I have heard are 4 hp per square foot of cooler surface in water below 55 F and 3 hp per sq ft for warmer water. BC warm!!

Lote of interesting information in your post. Thank you!. I had in mind to make the keel cooler using thin wall steel tubing as used in heating systems. It may not be as efficient as copper, but it is way cheaper, less electrolysis issues... and it will last longer than I will live!

 

[neurodoc]

McGillicuddy made a great post while I was doing mine about steel channel keel coolers for your steel hull boat. Could be the answer as long as you don't cause problems on the inside while welding on the outside. Sizing numbers I have heard are 4 hp per square foot of cooler surface in water below 55 F and 3 hp per sq ft for warmer water. BC warm!!

Unfortunately this is not an option. High risk of burning boat down!

 

[neurodoc]

I believe that we and the OP are overthinking this problem. To switch to keel cooling is a big change and significant money.


His current over heating problems could be simple to fix or not, but almost certainly cheaper than adding a keel cooling system. And that keel cooling system might have exactly the same problems, if the current system has a problem on its coolant side. Also he will have to keep the raw water system for exhaust gas cooling or install a dry stack system- more bucks!.


He said he could get the data I asked for early in this thread over the weekend. I hope he does so we can try to diagnose what is going on with his current system.


David

Hi David! Just called the exhaust manifold gasket manufacturer (they are custom made) and there is a delay in the manufacturing.... may be next week. So I will spend the weekend doing some painting maintenanace and having some good SIESTAS !

 

[DavidM]

Hi David! Just called the exhaust manifold gasket manufacturer (they are custom made) and there is a delay in the manufacturing.... may be next week. So I will spend the weekend doing some painting maintenanace and having some good SIESTAS !

OK, let me expand a bit on how to collect the data needed. What I want to do is make a heat balance around your main heat exchanger to try to see why it isn't performing.


So, either at the dock with lines tied down tight and in gear or underway, slowly speed up until the engine begins to overheat. Hold that speed for a few minutes to let temps stabilize and if it gets too hot, say 200 F or 93 C then back off to hold it near there. Check the coolant temp to make sure it is stabilized. Take temps in and out of both the coolant and raw water nozzles of the main heat exchanger with an IR gun. Note the engine rpm.


Then let the engine cool down. Loosen up the hose to the injection elbow so it can be quickly pulled off. Start the engine from cold and rev it to the rpm noted above but in neutral and quickly pull off the hose and put it in a 5 gallon bucket. Time how long it takes to fill and then reconnect the hose.


I know it may be messy so adapt to your situation, maybe use two buckets, one to catch the water after startup and another to catch it at the specified rpm. What we are trying to do is get an accurate indication of water flow at the rpm noted above to do a heat balance.


Reconnect the hose and let it run for a while until the temps stabilize. With no load presumably it won't overheat. Then take temps in and out of both sides as above.


We could speculate ad infinitum as to what could be wrong, but the foregoing data will provide some clues.


David

 

[FF]

"either at the dock with lines tied down tight and in gear"


In most marinas this is a NO NO as it will scour the bottom and can move large amounts of marina bottom into a channel.

 

[Brooksie]

Get yourself a copy of David Gerr's book "Boat Mechanical Systems Handbook" It has a very complete section on keel cooling which will tell you everything you need to know & more with charts for different size and material pipe length per HP. Also great sections on dry exhaust and many other subjects. Last year we keelcooled my friend's boat using Gerr's information and it came off w/o a hitch.

 

[mikecambrai]

Overheating and keel coolers

Fitting a keel cooler is not an easy job and they can be prone to problems with respect to bleeding and airlocks. I would suggest that you get working what you have first and as suggested start by checking the cooler end covers for debris from the previous owner's trials and tribulations. These Detroits do not like overheating and is the main cause of their demise.
I would suggest that 700 hp in a 55ft displacement hull is way over the top, and the engines would be struggling to produce too much horsepower at too little revs and be overheating anyway. 200 hp should be ample HP for this hull.
Bring up the boas speed to 8 knots which would be a good cruising speed, and watch the incremental revs/speed/temperatures.

 

[ben2go]

Hi, greetings from Tigre, Argentina!

I have a 55 Ft full displacement steel trawler with two GM 350 aspirated diesel engines.
The engine cooling is by means of heat exchangers + wet exhaust.
The system works ok at 50% of the engine´s power. At 80% or more, engines heat up.
I would like to change the cooling system to one of those used in fishing boats or commercial vessels: this is basically to attach a steel tube-serpentine to the outside of the hull, fill it with engine coolant system and eliminate the heat exchanger currently in operation.
Problem is I have no idea on where to get this information: already talked to a couple of mechanics, but their opinions difered a lot.
Anyone done the same before?
Please let me know your thoughts!

I keep pondering over the GM 350 diesel angle. If those are GM/Oldsmobile 350 gas engines that were converted to diesel in the 70's and 80'sby GM, then that may be your issue. They had overheating issues in autos after they got some mileage on them. The heads, from my understanding, weren't a very good design. Those engines were very inefficient for a diesel engine. The only good thing about them, in the US anyway, was that most GM 350 gas engine marine components would bolt onto them.

 

[sunchaser]

I keep pondering over the GM 350 diesel angle. If those are GM/Oldsmobile 350 gas engines that were converted to diesel in the 70's and 80'sby GM, then that may be your issue. They had overheating issues in autos after they got some mileage on them. The heads, from my understanding, weren't a very good design. Those engines were very inefficient for a diesel engine. The only good thing about them, in the US anyway, was that most GM 350 gas engine marine components would bolt onto them.

Hopefully not that one. I had a Chevy pickup with one. It was a disaster from the start.

 

[neurodoc]

neurodoc, I hope you sort this out, it is often pretty simple.

Great name for a boat by the way.

Thanks a lot for your comment! and Yes, the boats name is great: When I bought it, it had a stupid name (put together using the two first letters of the previous owner´s children... or so), as the boat had been neglected for a quite long time it was a real mess: nothing worked, everything was rotten, rusted or broken. I worked on it after work hours, weekends, holidays... for three looong years. Many things went wrong too many times, and had to be redone.... People who knew me well thought I would give up... but I did not! When thinking of a new name for the boat, the story of a madman called Fitzcarraldo (actually Fitzcarrald) who transported his steamship over a steep hill in the Peruvian Amazon (ca. 1920) came to me....
.
I have attached a picture; hope you can see it!

By the way: there is an excellent German Film (Captions in English) that tells the story

 

[Ski in NC]

I think his GM 350's are English Bedford straight sixes, no relation to the V8 automotive engines.

To the OP- Can you post some photos of the engines, especially showing coolant heat exchangers and related hardware?

 

[neurodoc]

In answer to your original question, I don’t think that what you are proposing is at all unreasonable. You have a steel hull vessel that runs at hull speed or less. However installing pipe on the hull does provide another failure point in the system in the event of a grounding. Gulf of Mexico steel shrimp trawlers work at high horsepower-low speed-shallow water while dragging big nets close to shore. Also shallow draft tugs have the same issue. The typical solution for them is to weld inverted C channel beam coolers on the bottom. This has several advantages. They are low profile and therefore low drag. They are strong and not easily damaged. They actually increase the longitudinal hull strength of the vessel. They provide more low weight thus increasing stability. They are pretty thick steel so erosion on the inside of the beams take a long time.
Disadvantages are the hull plating head to have sufficient thickness remaining to support the water flow through the channels. No point having 12 mm thick channel coolers if the bottom thickness remaining that they are attached to is only 5 mm. Also, channel coolers remove the ability to water cool the exhaust. So a dry stack would have to be installed. In my view, this is not a bad thing as it removes underwater through hull penetrations which is always a good thing.

As for calculations on how long the runs will be? The fishermen use seat of the pants calculations. Typically I see two runs of 20-30 feet per 350hp engine. The ends are joined together with a short piece of channel. You might actually have a little too much cooling with this set up but that is easily controlled with an appropriately sized thermostat.

Or you can go with a pre-engineered grid cooler such as Fernstrum as mentioned by others. Advantages/disadvantages are discussed in earlier butI would definitely inset that type of cooler in the hull or provide some type of protection for the softer metals in the cooler. That would be a viable solution if a little more expensive.

Good luck and let us know how you decide to proceed.

Very interesting! If I had to choose, I also would have gone for inverted "C" channels welded to the hull.... but it is too late for that (high risk of fire).
I will start gather as much info as possible and when getting the boat on the hard (quite soon) I will flip a coin and decide the way to go.

 

[neurodoc]

I think his GM 350's are English Bedford straight sixes, no relation to the V8 automotive engines.

To the OP- Can you post some photos of the engines, especially showing coolant heat exchangers and related hardware?

Hi! you are right: these Bedford are straight sixes originally developed in the UK and later on mass produced in many counties. General Motors of Argentina used this engine (as it was designed) in 5 Ton trucks during the mid 60´s and later increased HP and performance by making a number of modifications on it. Here it was produced until the mid 80´s. A large number of these remaining engines were used in harvesting equipment, work boats and gensets.


I will take some pics and post them quite soon.
In the meantime, a picture of the original Bedford found on the internet: (this one has a linear Bosch pump, while the engines on my boat have AGV UK made rotary diesel pumps).

 

[neurodoc]

Hopefully not that one. I had a Chevy pickup with one. It was a disaster from the start.

Those engines were V8 and a complete nightmare for GM, for many years: The ones I am talking about are real indestructible workhorses !

 

[neurodoc]

Get yourself a copy of David Gerr's book "Boat Mechanical Systems Handbook" It has a very complete section on keel cooling which will tell you everything you need to know & more with charts for different size and material pipe length per HP. Also great sections on dry exhaust and many other subjects. Last year we keelcooled my friend's boat using Gerr's information and it came off w/o a hitch.

Good advise thak you!

 

[neurodoc]

I believe that we and the OP are overthinking this problem. To switch to keel cooling is a big change and significant money.


His current over heating problems could be simple to fix or not, but almost certainly cheaper than adding a keel cooling system. And that keel cooling system might have exactly the same problems, if the current system has a problem on its coolant side. Also he will have to keep the raw water system for exhaust gas cooling or install a dry stack system- more bucks!.


He said he could get the data I asked for early in this thread over the weekend. I hope he does so we can try to diagnose what is going on with his current system.


David

Hi David, I will do this quite soon. So far, one engine is still down because gaskets were not delivered on time, on the other hand, walking around barefooted I broke / displaced mi right index finger toe and will have it straightened by means of a nail. Surgery is on Friday. Will be out tied to the bed for some days

 

[ben2go]

Hopefully not that one. I had a Chevy pickup with one. It was a disaster from the start.

78-85 and I was glad those fell out of favor quick. I worked on a few when I was an auto tech in the '90s. I saw most of them in the junkyards and A few guys bought them and converted them into hot rodded gassers.


https://en.wikipedia.org/wiki/Oldsmobile_Diesel_engine

I think his GM 350's are English Bedford straight sixes, no relation to the V8 automotive engines.

To the OP- Can you post some photos of the engines, especially showing coolant heat exchangers and related hardware?

Thankfully this was confirmed. There's little info that I can find around the interent about them. I must say, that I know little about the Eng Bed engines.

Hi! you are right: these Bedford are straight sixes originally developed in the UK and later on mass produced in many counties. General Motors of Argentina used this engine (as it was designed) in 5 Ton trucks during the mid 60´s and later increased HP and performance by making a number of modifications on it. Here it was produced until the mid 80´s. A large number of these remaining engines were used in harvesting equipment, work boats and gensets.


I will take some pics and post them quite soon.
In the meantime, a picture of the original Bedford found on the internet: (this one has a linear Bosch pump, while the engines on my boat have AGV UK made rotary diesel pumps).

Those engines were V8 and a complete nightmare for GM, for many years: The ones I am talking about are real indestructible workhorses !

This is good to hear. Unfortunately, I don't know enough about your engines to offer advice specifically about them. All I can do is parrot what others are saying. I will be watching and learning.

 

[ben2go]

Hi David, I will do this quite soon. So far, one engine is still down because gaskets were not delivered on time, on the other hand, walking around barefooted I broke / displaced mi right index finger toe and will have it straightened by means of a nail. Surgery is on Friday. Will be out tied to the bed for some days

Heal well and heal fast. Good luck with surgery.

 

[neurodoc]

I have no advice to give on you cooling system design, but just wanted to say I have been to Tigre and it is beautiful.


Are your engines getting to the correct RPM at full throttle? If not, you may be over-propped which would cause the symptoms described.

Hi, sorry for the late reply. a lot has happened since. I have the feeling the props are ok or slightly under - propped. Nevertheless I will have this checked as well when on the hard quite soon.

 

[neurodoc]

OK, let me expand a bit on how to collect the data needed. What I want to do is make a heat balance around your main heat exchanger to try to see why it isn't performing.


So, either at the dock with lines tied down tight and in gear or underway, slowly speed up until the engine begins to overheat. Hold that speed for a few minutes to let temps stabilize and if it gets too hot, say 200 F or 93 C then back off to hold it near there. Check the coolant temp to make sure it is stabilized. Take temps in and out of both the coolant and raw water nozzles of the main heat exchanger with an IR gun. Note the engine rpm.


Then let the engine cool down. Loosen up the hose to the injection elbow so it can be quickly pulled off. Start the engine from cold and rev it to the rpm noted above but in neutral and quickly pull off the hose and put it in a 5 gallon bucket. Time how long it takes to fill and then reconnect the hose.


I know it may be messy so adapt to your situation, maybe use two buckets, one to catch the water after startup and another to catch it at the specified rpm. What we are trying to do is get an accurate indication of water flow at the rpm noted above to do a heat balance.


Reconnect the hose and let it run for a while until the temps stabilize. With no load presumably it won't overheat. Then take temps in and out of both sides as above.


We could speculate ad infinitum as to what could be wrong, but the foregoing data will provide some clues.


David

I got the idea and agree with you on applying a "scientific method" to diagnose the problem and find a solution. Unfortunately due to a surgery on my toe next Friday, this may have to be delayed for some weeks. I will be around as soon as my doctor sets me free.

 

[neurodoc]

"either at the dock with lines tied down tight and in gear"


In most marinas this is a NO NO as it will scour the bottom and can move large amounts of marina bottom into a channel.

My boat is in a German rowing and Yachtclub, so it will get a NEIN NEIN !

 

[neurodoc]

Bedford 350 6 straight + Cooling Syetem

HI there, I just found some images from the new cooling water tray I made to replace the corroded original which was casted aluminium. I built it in 304 SS in two halves: the inferior half contains the exhaust manifold and a "U" shaped radiator for gearbox oil.
The upper half contains the engine coolant heat exchanger, which is built in copper. Both halves are screwed together with a gasket in between forming a "box" measuring about 1 meter (3Ft) x 30 (1Ft) x 30 (1 Ft) that runs along the engine. The exhaust manifold has an elbow on the back on which a vertical "tank" is attached to. Inside this tank gases are mixed with water leaving the SS "box", before being evacuated trough the exhaust hose.There is also a picture of the engine which I took last evening after installing the new exhaust manifold gaskets. Everything is a mess due to exhaust gases. tar, oil, coolant...

So far I did my homework! Tomorrow surgery... and in 10 days (God provide ) some scientific testing of the cooling system as Dave suggested

 

[FF]

Looking at the size of the boat and the installed engines , I would guess going faster is not the goal, perhaps making better headway in a bow on breeze is the goal.

I think I would install EGT gauges for each engine and accept the slower speed in bad conditions.

 

[neurodoc]

Looking at the size of the boat and the installed engines , I would guess going faster is not the goal, perhaps making better headway in a bow on breeze is the goal.

I think I would install EGT gauges for each engine and accept the slower speed in bad conditions.

I agree with you: The cruising speed of this boat is 7.5 Knt @ 1800 RPM. And my brain is set to that speed If I increase RPM´s up to 2500 ... fuel consumption skyrockets, while speed increases perhaps in 2 Knt (can´t recall exact figure right now)

No idea on how EGT gauges info is understood and how to apply the reading from these gauges on actual driving behavior of the boat.