View Full Version : How does a raw water cooling system work?

03-12-2009, 10:24 AM
This may sound strange....but how does a raw water cooling system operate?

In a standard closed cooling system, the water is circulated, and when it reaches a specific temperature, the thermostat opens, water then passes the radiator, which is cooled by a fan, returning to the block, etc, etc.

So how does my raw water system work?

It draws water in, but i dont have a radiator, nor a fan, and the water is returned back out the exhaust........after circulating the system once???

If not....how is is kept in?

Do i have a thermostat? If so...where is it....and what purpose does it serve?

Anyone have a web link to a diagram?

p.s. i must have too much time on my hands.....

03-12-2009, 10:42 AM
There is a hole in the bottom of your boat, it picks up raw water from the lake. It is pulled into your boat to the engine via the raw water pump (impeller). From there it is pushed into the engine block at the thermostat housing. Yes you have a thermostat. Some of the water waits there until the engine is up to temp and then flows through the block cooling your engine. The other part of the water is routed to the exhaust manifold to cool and silence the exhaust. That is the basic outline.
Your transmission is cooled by raw water prior to the impeller pump.

03-12-2009, 11:06 AM
Thank you .....

I will change both thermostats to be safe.

03-12-2009, 12:04 PM
Thank you .....

I will change both thermostats to be safe.

Both thermostats?

03-12-2009, 12:52 PM
Yes, both, seemingly there are two on my system.........
"Indmar LT 1 engines use 2 thermostats, the 160 goes in the intake manifold (like a car) and a 143 in the triangular housing." to quote SKIDIM.COM

03-12-2009, 08:12 PM
the water comes in the raw water pump (impeller) is pumped into th exhaust to heat the water some so ice cold water water is not going into your block.and at the same time cools the exhaust. then fills the block for cooling. when the water getts to 160 the thermostat opens and the water is excanged with new water.

03-13-2009, 04:28 AM
Scrap my last statement......only 1 thermostat.......but for some reason my manual lists two.

03-13-2009, 01:51 PM
Maybe two different applications for the same engine.

03-13-2009, 05:00 PM
Does anyone have any information on the volume (gph) that the raw water pump produces? I've made a garden hose adaptor that connects to the raw water pump inlet for winterizing and redeployment in the spring. I find that the garden hose begins to collapse and I'm worried that the pump on the sand point well at my cabin can't provide sufficient flow volume to meet the demands of the pump at idle.

03-14-2009, 09:15 PM
Wolfstone - sorry to hijack the thread, but my wife and I are traveling to London in early May. It'll probably be way too cold still, but if for some reason the weather isn't too bad is there a place to rent a boat for a day or an afternoon? Just curious and saw you were in Stroud. Had a crazy thought that it would be cool to say I've wakeboarded in England!

By the way - I was in Stroud in 2004 and loved it there. I work for an oil company that has a location there and got the opportunity to go for a week. My wife wasn't able to go then, so this will be her first trip abroad. Planning on taking a day trip to the Cotswolds. We're staying in London, so any other must do's would be appreciated!

03-15-2009, 06:09 AM
Way too cold in May....?
We start boarding first of April.
The water will be about 50degrees fahrenheit....but thats as good as it gets until summer when it might warm up t 60 degrees or maybe 70 in a very warm year!

I don't know of any places where you can hire a boat for boarding in the U.K., but you can hire tows at the Watermark Club on a lake in the Cotswolds, just google watermark club in cotswold water park and youll find info.