caltexflanc
Guru
neurodoc, I hope you sort this out, it is often pretty simple.
Great name for a boat by the way.
Great name for a boat by the way.
The boat is 40 years old. The first owner passed away. The second is a jerk....
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
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!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!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!!
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 !
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.
neurodoc, I hope you sort this out, it is often pretty simple.
Great name for a boat by the way.
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.
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?
Hopefully not that one. I had a Chevy pickup with one. It was a disaster from the start.
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.
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
Hopefully not that one. I had a Chevy pickup with one. It was a disaster from the start.
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).
Those engines were V8 and a complete nightmare for GM, for many years: The ones I am talking about are real indestructible workhorses !
Heal well and heal fast. Good luck with surgery.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
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.
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
"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.
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.