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  #41  
Old 09-07-2021, 05:04 PM
FLexpat FLexpat is offline
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Volvo Penta used the crank mounted pumps on the SBCs for years. Marine Power as well. I have had them and was pretty happy even though it took me a bit to trust it. The way they use a rubber bushing around the arm bolt takes up a lot of flex/vibration. You can change the impeller pretty easily and if you have it set up with shutoff valves, you can do that in the water. My only concern would be getting enough cooling since it looks like you will end up with a pretty high performance motor.
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  #42  
Old 09-08-2021, 01:01 AM
Xcomunic8d Xcomunic8d is offline
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Brother you just hit my greatest concern. I have no idea if this will be adequate cooling.

I bought a 350,000 BTU heat exchanger and you can see my diagram below. I figure I’ll spend a small fortune in fittings and hoses but throughput is gonna be the name of the game. Assuming this cools adequately keeping it flowing is next priority.

It does have a shut off valve on 1.25” water inlet to strainer, to pump, to various fittings. I’m running the biggest hoses I can think of and utilizing both sides of elbows in/out to promote quick circulation.

I have a friend that runs the biggest cooling, refrigeration hvac (grocery stores etc freezers and a/c) for the island/state. He did some math and recommended this setup. But between us, I have no clue of this will work. Only one way to find out I suppose.

Last edited by Xcomunic8d; 09-08-2021 at 01:04 AM.
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  #43  
Old 09-11-2021, 08:53 AM
FishStretcher FishStretcher is offline
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Do you have more specs than just 350,000 BTU/h? At what temperatures, flows, etc?


I have done these sorts of calculations for piston aircraft engines- I *might* be able to help.





Quote:
Originally Posted by Xcomunic8d View Post
Brother you just hit my greatest concern. I have no idea if this will be adequate cooling.

I bought a 350,000 BTU heat exchanger and you can see my diagram below. I figure Iíll spend a small fortune in fittings and hoses but throughput is gonna be the name of the game. Assuming this cools adequately keeping it flowing is next priority.

It does have a shut off valve on 1.25Ē water inlet to strainer, to pump, to various fittings. Iím running the biggest hoses I can think of and utilizing both sides of elbows in/out to promote quick circulation.

I have a friend that runs the biggest cooling, refrigeration hvac (grocery stores etc freezers and a/c) for the island/state. He did some math and recommended this setup. But between us, I have no clue of this will work. Only one way to find out I suppose.
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  #44  
Old 09-11-2021, 02:34 PM
Xcomunic8d Xcomunic8d is offline
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40 GPM 4-1” ports on exchanger. Rated at 350,000 BTU. Using 1.25” hoses to feed water into and out of exchanger. See post 30 for thorough diagrams of system.

About all I know on it. 5.3 engine. 400-450hp output is my guess expect to spend most of my time 1500 rpm for trolling.

Any help greatly appreciated. I’m trusting other people on this one.

Last edited by Xcomunic8d; 09-11-2021 at 08:34 PM.
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  #45  
Old 09-13-2021, 08:15 PM
FishStretcher FishStretcher is offline
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I can only offer you a modest amount of guidance based on experience with other engines.



I did a fair amount of cooling work on Rotax 912 IS sport 100hp 4 cylinder aircraft engines. These were liquid cooled heads, but air cooled cylinders. And an oil cooler.



Crucially, they can operate for a long time at or near full power, like a marine engine.


For a 100HP engine (metric HP, but close enough for what we are discussing here) they were rated at 73.5kW for 5 minutes or 72kW continuous


Go to flyrotax.com and look for the installation manual for details: d06847.pdf


They required 30kW of liquid cooling, 6kW of air cooling and 10kW of oil cooling for takeoff. Takeoff is the worst condition, especially for oil cooling because of this highest engine speed.


In my experience, this air cooling was largely unneccesary except at above 80% power.

So, if we think the GM 5.3 is more efficient than a Rotax 912 iS Sport, and it probably is, then an estimate would be 30kW of water cooling 6kW of air cooling and 10kW of oil cooling for every 100HP at the crank.


So for the estimate: for every 100 metric HP you make 73.5kW shaft power and need 46kW of cooling.

Again, the 5.3 may make less heat, it's a modern engine.



You say you cam make 400HP. That's at WOT, at maximum engine speed. Power requirements are very approximately related to the cube of speed. So at 80% speed, you will need very approximately 51.2% power. (and heat rejection). Or 200HP.


So at 80% speed at 200HP, you need 2x(30+6+10)kW cooling. Call that 92kW heat rejection.


You have 350,000BTU/h heat rejection. My online calculator and a couple of references make me think this is 102.5kW.



So. For a first guess- I think you might overheat running at full throttle at full engine speed. But you are probably fine for almost all operation.


This is just a guess- a slightly scientific guess with a reference, but just a guess. You could be OK at all speeds. I don't think this is a terrible place to start for cooling. But it doesn't seem overcooled.


Remember, this is just an opinion that you got on the internet, using a different engine as a benchmark.
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  #46  
Old 09-13-2021, 08:47 PM
Xcomunic8d Xcomunic8d is offline
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It has occurred to me that I made an error in telling you it will only be 350k btu’s. That’s the main heat exchanger however there will be additional 50k (25k for power steering and oil each). So I’ll try to figure out what that looks like.

Heat soak is also a concern. I plan to have a bilge vent blower on the bilge exhaust side keyed to ignition so it pulls hot air out of the compartment and should draw cooler air in naturally. This blower is not to be confused with another blower I will install for venting gas fumes.

Thanks for doing all this math. There really is only one way to find out for sure. It will have a ps cooler and an oil cooler.

If needed a bigger exchanger is not the end of the world. But we will see. I’ll get up on plane and get going fast on rare occasions but majority is high speed trolling. 13mph. Give or take conditions.

Last edited by Xcomunic8d; 09-14-2021 at 01:19 AM.
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