Why do our engines need raw water?

[gride]

I'm sure this is an insanely moronic question, but why do our engines need lake/river water? I've got the same engine in my truck. Also, why install a partially closed system on PCM engines when crusaders get fully closed?

[AirTool]

I'm sure this is an insanely moronic question, .... ?

I agree.

[Drock]

You could bolt a radiator on the front of your boat, but it may block your passengers view

[gride]

Airtool: notice our relatively similar join dates vs. number of posts. The funny thing to me is that mine are all questions and yours are all well explained answers.

[AirTool]

You could bolt a radiator on the front of your boat, but it may block your passengers view

I thought it but didn't say it. I have a 99 Tahoe with the same engine as my 206. So, give or take, here is the radiator we'd need:

http://www.rockauto.com/catalog/moreinfo.php?pk=325091

Note with the crappy Vortec intake/gasket design, after a year or so of running at 15 psi instead of atmospheric, we'll need to replace the intake manifold gaskets. Might as well just do it straight away before glycol/water goes down in the oil.

Oh, we'll need to change out the exhaust system to open headers or something not requiring dumping large quantities of cooling water in to keep everything from melting.

But at least we'll be able to get rid of that pesky impeller that takes three minutes to change.

[AirTool]

... and yours are all well explained answers.

Well...except for maybe post #2 above.

[gride]

Hey, I don't mind changing my impeller. It's easy as can be. I have limited knowledge on combustion engines besides the fact they are extremely inefficient. And airtool, you're always welcome to poke fun at me because I've received bountiful amounts of knowledge from you on this site.

[AirTool]

One other trivia note:

Give or take, for Otto cycle engines like the ones in our boat...a rule of thumb for the energy use from burning the fuel is:

1/3 out the output shaft in the form of fun (some consumed by the accessory drive belt/water pump/alternator/etc)
1/3 out the exhaust in the form of heat
1/3 out the cooling system in the form of heat

[SkiTundra]

1/3 out the output shaft in the form of fun (some consumed by the accessory drive belt/water pump/alternator/etc)
1/3 out the exhaust in the form of heat
1/3 out the cooling system in the form of heat

Wonder how this compares to an electric drive.

[DanielC]

This is how it compares to an electric drive.
I believe the battery in a Chevy volt is rated at a capacity of 16 KWH. That means it is capable of supplying 16,000 watts of electricity, for an hour. That sounds like a lot of electricity, and actually, it is, as far as electrical measurements go.
To convert watts to horsepower, you multiply horsepower by 746. Or divide watts by 746 to get horsepower. 16,000 watts / 746 = 21.447721 horsepower.
The battery in a Chevy volt will supply slightly less than 21.5 horsepower, for an hour. Then it has to be charged for several hours.

My boat will run for an hour on about three gallons of gas.

[DanielC]

Now, back to the radiator vs lake water cooling.
You will need a radiator quite a bit bigger than the radiator in your truck. At WOT (Wide Open Throttle) your boat will do maybe 45 MPH. 45 MPH on your truck is a part throttle cruise, even when towing the boat. So, where do you put the radiator?
Remember, you have to supply air to the radiator, and pass the hot air away from it after it goes through the radiator, one time.
By the way, with a boat, you have to get the hot engine exhaust out of the boat. Without raw water cooling, you have exhaust that is several hundred degrees going through fiberglass bulkheads, and out the transom. These exhaust parts would have to be made of metal, sealed, and insulated from the rest of the boat.

Why not just suck cool lake water into the engine, use part of that for cooling the engine, and dump the rest of it out the exhaust, cooling the exhaust, and not have to deal with a huge air radiator, and getting air to, and away from it.

[srock]

You have an inexhaustible source of coolant all you have to do is pump it. The "water" is a very efficient place to dump heat and it remains nice and cool at any speed. In a closed system the heat exchanger is a fraction of the size of a car radiator which illustrates the level of efficiency. Larger boats also dump the the air conditioner heat into the lake. All make sense? Simple.