Water Flow

[Poida]

Hi just joined the forum as I was looking for info on water cooling.
I have had a timber 6m (20') power boat with a marinised straight 6 motor GM.

This boay may have changed hands a few times and I am checking with anyone who may know if the water cooling is set up properly.

The engine uses raw water, which is pumped into the engine block, runs up into the head and out to the exhaust manifold. As one would expect.

But also about 1/4 of the way up the engine from the rear, obviously it tilts for the prop shaft, there is the fitting where the temp. gauge is fitted with a hose running to the heat exchanger of the small marine gearbox, then also to the exhaust.

Why would you run hot water to the gearbox? I was wondering if it has been altered by a previous owner or if in fact the gearbox is supposed to be kept warm.

Does anyone know the direction of water cooling flow?
Thanks if you can help.

[bilgeboy]

Not sure if that is a stock set up or not. I am pretty sure the arrangement is not to keep the gears warm, though. Cooler gears last longer.

My diesels get cooled AFTER the gears. This arrangement makes sense to me, since I figure the thermal load from the transmission fluid is a tiny fraction of that produced by the engines. Why not take care of the little guys first?

After really spending some time thinking about your cooling system, I think you will feel comfortable modifying for improvements. Shorter hose runs are key in keeping resistance to flow down, as well as eliminating sharp angles, etc, etc. Its not brain surgery. You will be able to figure out direction of flow very quickly with a bit of investigating. Exhaust is last, pickup is first - you will be an expert in no time.

Good Luck,

Mike

[gonzo]

The usual installation makes the water go through the gears first.

[Poida]

Thanks guys, that's what I thought. Must have been changed by a previous owner.