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View Full Version : cooling water basics,...I don't understand



oldLenny
12-28-2002, 12:33 PM
Looking at all the systems available, reversion principles etc, and my total lack of understanding any of it, what would the best way to go be, if money were no object?

I see sea-strainers, what do they do? transom mounted pick-ups, through hull pick ups, etc, "water dupms", what do they do? and if they separate the cooling water from the exhaust, why not use this method instead of putting it into the exhaust?

Is by-passing the pick-up on the leg the best way to go?

And Geoo, how do you cool the 383 (or whatever) at 106 and basically an airborne hull no leg?

I am trying to understand the whole cooling thing and the best system, but need to understand a basic one first...uneducated,...Lenny

Bryan Tuvell 33ZX
12-28-2002, 02:28 PM
Hi Lenny, there sure is alot of different ways to cool for sure, of course I am stock, there are some great threads here and other places (OSO) on water pick up, by pass set up etc, try a search.

Just left my buddy's house, looking at twin 650's, with dry exhaust CMI's with water dumps out the transom, crossover type set up...
Best of luck, see you in the chat room again soon.
Bryan

fasttrucker
12-28-2002, 06:17 PM
My 1998 28zx was set-up wrong from the factory.It was a new product/design...anyway my performance meck.put in a sea-strainer from teague.1)keeps the grass out.2)keeps the water supply to the engine full.He also filled in the upper water intake holes so as to not suck in air.So the seastrainer performs two functions,the constant water flow being the most important...dont burn-up your motor. :rolleyes:

Formula Jr
12-30-2002, 04:56 AM
Thru hull pickup systems:
These are the oldest design, and are still used for various ski boats and larger boats with direct or Vee drive type drive systems. You'll find these with very early volvo and eaton i/o drive systems, and Speedmaster lowers.

Transom mounted water pickups:
This is a newer solution to the fact that boats air-out more than they use to so the pickup had to be moved back to the transom. Used with Vee drives, direct drives, arnesons and Speedmasters.

Jetboats have the intake off the impellor tunnel - a very simple design..

Drive intake:
These typically use an impellor assist in the drive. The high water intakes are along the sides of the lower unit. Some have lower water intakes that are at the front of the leading edge of the lower unit. Very small holes by the way, cause the water pressure there is enormous at speed.

Cooling can be Freshwater, semi-freshwater, raw water or non exsistant in some drag boats.

Total fresh water designs, never let any raw seawater touch the internal engine water jackets. Its just like an automovive design, but instead of a radiator, you have a heat exchanger. Raw water flows over and through the exchanger, where heat is transfered from the closed system of anti-freeze and water mix sealed in this isolated system to the sea water. You need two pumps with this system. One is usually the drive impellor that circulates raw water through the exchanger, then back out the exhaust at the risers. The other pump is the motor mounted water pump that circulates the anti-freeze solution thru the engine and the exchanger. My Seaswirl is a freshwater system.

A raw water system - not recommended for salt - doesn't use a heat exhanger. You're just running raw water throught the whole system. You only need one pump for this, but most people still use both: the impellor, if they are using a legg, and a belt driven water pump - redundant, but it gets you home. My JR and GT are raw water systems with legg and engine pumps.

Raw water engines you will want to run cold, below 190 F, cause salt will percipitate out of solution at higher temps and coat the system. This is an engine killer. The boat I think you want to build, should have a freshwater system. You can have that with a transom pickup also. Forget the sea strainers for your area, cause kelp blocks the whole intake.

Gearhead99
12-30-2002, 08:15 PM
Nice looking pick up there.

Defeniatly the last piece of hull in the water.

BigGrizzly
12-31-2002, 02:35 AM
Everything has been said. I have a closed cooling system on all my boats now and will never go back. the temps are more even and fuel is better used. No outside material from swawater enters the block and with Anti-freez winterization is a snap. I have a Transom pick up in all the boats. if the pump fails it still has 10->15 PSI of pressure at speed so this isn't abig problem. Circulayion pump failure isn't any different than a car providing using antifreez for lubrication it leaks befor it seziez so green stuff is a teltail.All the systems work but what I have learned recently I would always use a circ pump for more even temp in the engine. I will say that I have not had any problems with the crossover system but I always used one with a by-pass and a t-stat.

GEOO
12-31-2002, 06:08 AM
Lenny,
I think Jr. said it all...
Fresh water cooling is the best. Engine system is all you need, the exhaust can be raw water cooled. However fresh water cooling is expensive, need space for the heat exchanger and it needs to work (no air bubbles etc..)
If you go ith a transom or thru the bottom pick up it is a crap shoot. The pick up may pick up too much water (too much pressure, blow head gaskets) too little pressure (over heat engine). You have to install the pick up and test it. The less it grabs the water the less drag the faster you go but the less pressure you have. Some have adjustable heights.
Water strainers help stop debris from getting in to engine and help keep water in system while airborn.
I have a transom mount pick-up with a screen on the bottom. I'm switching to a bottom pick-up.( I'm, switch trim tabs and the new ones won't fit with the water pick-up on the transom). The bottom pick-up does not have a screen so I will install a strainer in the boat.

riverrat
12-31-2002, 10:05 AM
What's wrong with going stock merc cruiser motor/alpha in the '16? eek!

BigGrizzly
01-01-2003, 02:56 AM
The closed cooling system I use is very small and is mounted of the engines in all my boats. there is an expantion tank mounter on the firewall higher than the higest water output to keep air out of the system. On the Criterion which os a blown 502 it is only30 inches long and 4 inches wide and mounts accross the stringers. the total addition of weight including hoes circulating pump and expantion tank and additional water is 56 punds. Best of all I no longer monitor water pressure and I use do it all the time with a bypass valve. BTW max safe pressure is 26 PSI, especially on blower ans high HP motors. One guy I know though he had reversion but water pressure was the real problem.

HyperDonzi
01-01-2003, 01:28 PM
On those water impellors that get dry and burnt out from catching air, where are those and how hard are they to replace?

Formula Jr
01-01-2003, 02:29 PM
Drive impellors don't burn out cause of air time. They burn out cause some fool fires up their motor without water muffs on the drive while its on land. Some people don't realize that the impellor is always spinning, the drive is always spinning, even if the drive is out of gear.

CDMA
01-01-2003, 11:52 PM
Grizz,

Water pressure being too high creates issues with head gaskets correct? One thing I always wondered...pressure in the combustion chamber is a heck of a lot more then 26 psi...why can the water jacket pressure only be 26psi? Seems odd to me that pressures in the chambers can be so high yet the water pressure has to be so low....not doubting just wondering.

Chris