Crossover vs. Circ. pump

[geerbox]

I have read other threads regarding the question which is better crossover tubes or the circulation pump. I am getting into my cooling system and I've found horrible rust. I think I need to pull the pumps off and take a closer look at the impeller. The hose barbs on the t-stat housing are falling apart when removing hoses and chunks of rust are falling out of the hoses. I have been looking at replacement t-stat housings, but now I think my circ. pumps might not be very good. I would like to replace with crossovers and new t-stat housings, but I have heard I might need to drill the thermostat to do this. I do not where or what size to drill and if it's totally necessary. I have twin 454s pretty much stock. Any suggestions? Is there really a hp gain from doing this?

[gcarter]

I've read circ pumps can take 4-7 HP, some even more.....it all adds up.

[Cuda]

I've got cross overs in my Formula, and circulating pumps on my Donzis. I've heard of people who have had excess water pressure problems with crossovers, though I haven't experienced any. They were on the boat when I bought it. I might also point out, I have no thermostats in the Formula.

I just took the hoses off the 25 year old t stat housing on Deb's 22, and there is virtually no corrosion at all. It would be easier to put a new housing and pump on, to save plumbing issues.

[maddad]

If the crossover and t- housing have a bypass port, there is no need to drill the t-stat. The bypass will get the exhaust all the water they need when the t-stat is closed.

[d1mbu1b]

So, what is the water flow circulation path for both T-stat conditions using the cross over?


T-stat closed:
raw water pump to T-stat housing
t-stat housing to exhaust manifolds

T-stat open:
raw water pump to T-stat housing
t-stat housing to intake manifold to heads
heads to block???
block to crossover???
crossover to t-stat???
t-stat housing to exhaust manifolds

What creats a circulation path through out the block and heads if there is no circulation pump? Is it the size of the ports on the t-stat housing and crossover?

[Cuda]

What creats a circulation path through out the block and heads if there is no circulation pump? Is it the size of the ports on the t-stat housing and crossover?
The sea water pump.

[Cuda]

I ran across this the other day on engine cooling.

http://www.perfprotech.com/home/techtips/warm-manifold-cooling-tips.htm

[MOP]

The only engines that need a circ pump are closed systems, any raw water cooled engine can run a cross over. The supply is the drive or engine driven sea pump feeding water to the Tstat/cross over it then dumps into the riser via Tstat or cross over by-pass.
The BS about cross overs adding pressure to the system is just that BS! The inlet supply "vs" the amount the riser will flow out is what dictates the pressure, the type of pickup drive "vs" transom has a lot to do with it. Big Griz has seen pressure near 100lbs with a transom P/U, also Hi/Lo water pickup drive like late Bravo diesel adds more pressure to the system then a standard side intake drive. I put a late Bravo on my 22 after having run a Blackhawk drive the pressure difference between the two was surprising.

Mind you head gaskets start to weep on the outer edges over 30-35lbs, that is what causes the rust stains hiding behind you exhaust manifolds.

Phil

[BUIZILLA]

alrighty then..............

who has dumped their circ pump on an Alpha drive, and used the crossover only with the drive pump?? :confused:

[geerbox]

Here is a picture of the starboard side t-stat housing, I think the hose barbs will crumble pretty easy. So, if I get a t-stat housing with a bypass, I will be ok? I have a hose going to each riser and each manifold, do I eliminate the hose going to the riser, or make a jumper. The water should flow through the manifold to the riser, right? Is that enough water?

[Cuda]

alrighty then..............
who has dumped their circ pump on an Alpha drive, and used the crossover only with the drive pump?? :confused:
Personally, I don't think an Alpha will pump enough water. I know that Budman had a sea water pump installed on the engine he just had made. Seems to me that every Alpha has steam coming from one side, which I would attribute to lack of cooling water, but I could be wrong. Gcarter has a crank mounted sea water pump, but I don't remember if he kept the circ pump or went with a cross over.

[gcarter]

alrighty then..............
who has dumped their circ pump on an Alpha drive, and used the crossover only with the drive pump?? :confused:
My boat was like that when I got it. Of course it didn't run either....frozen w/about 5 gallons of saltwater/oil emulsion in it.
But, like Joe mentioned, I did go w/ a crank driven seawater pump pulling from a transom pickup.

[gcarter]

Gcarter has a crank mounted sea water pump, but I don't remember if he kept the circ pump or went with a cross over.
I did utilize the crossover to mount a Meziere electric circulating pump for the closed cooling system.

[Cuda]

I did utilize the crossover to mount a Meziere electric circulating pump for the closed cooling system.
Picture?

[d1mbu1b]

I've got cross overs in my Formula, and circulating pumps on my Donzis. ... I might also point out, I have no thermostats in the Formula...


So now you have the choice to run a thermostat and a bypass from the crossover to the t-stat housing for when the t-stat is closed
-OR-
no bypass and no thermostat and let the water flow simply in the crossover, through the engine, and out the thermostat. This sounds like a super clean and simple configuration.

What are the disadvantages?
A long time to warm up the engine?
It seems most of the boating we do is when its warm out anyway.

[gcarter]

Picture?
Here ya go;

http://www.donzi.net/forums/attachment.php?attachmentid=20477&d=1146928687

[BigGrizzly]

As for crossover causing problems is not BS. Anything over 35psi in the block is detrimental to head gaskets. It just happens to be more prone to the problem then circ systems, circ systems have it too just not so much due to application Race boats have relief valves for this reason. think about this the first place the cold water hits is the front of both heads than block then t-stat. if the state is open, takes a while to close, then the exhaust. Garry Grimes designed the one tat Mercury sells. If you look at some engines and you see rust from the head down the block this was probably the cause. This is especially true on blower and high compression engines. with a circ the impeller restricts the flow of warer. Now in most applications that the average 65-70 mph unit it is on the verge, especially with hull pickups and re entry. My Criterion would surge upto 32 psi at 78 untill i put on the closed system. I won't go into the temperature differential thing because have done this on the net before. Believe me it does exist.

[BUIZILLA]

alrighty then..............
who has dumped their circ pump on an Alpha drive, and used the crossover only with the drive pump?? :confused: :wink:

[ALLAN BROWN]

The alpha pumps enough for a small block, probably not for a big block. If you have that combo, you may need to weld up some of the bottom holes on the riser dumps to force the cooling water to the top when idling (to keep your skin from sticking to it)

No matter what you do when you remove the circ pump, you must introduce the water into the same two holes that the circ. pump did.

If you run a thermostat on the crossover application (a must to me), you must drill 3 5/32" holes in the crown of the thermostat to allow water to bypass at all times. All thermostats are automotive based, and are expected to have the same (more or less) temperature on both sides of it. If you install a standard thermostat, the temperature will spike LIKE CRAZY.

The circ. pump belt is a fractional horsepower belt. How long do you think it would last on a 20HP Go-Kart?

[Barry Eller]

I had to drill holes in my T-stat with my crossover. Temps went high real quick before the holes were drilled. The bypass does not flow enough water.

[d1mbu1b]

if you have to drill the t-stat to bypass hot water when its shut, why not just remove it.

What is the advantage to running with a thermostat.
. warming up the engine ?
. emmissions are less with hotter chambers ?
. heat exchanger will have more time to suck the heat out of the fresh water ?
. I must be missing the biggie. what is it ?

When I was a kid I always took the t-stat out of my cars in the summer and only ran them in the winter.

running w/out a t-stat:
. will run cooler
. reduce potential for detonation for those on the edge
. eliminate the potential for the t-stat to get stuck closed then overheat
. simplify the cooling system using a crossover
one hose to the raw water pump to..
one host to the crossover
two hoses from the t-stat housing, each to the exhaust manifolds.

[Barry Eller]

T-stat will restrict waterflow enough to let water cool engine. Without T-stat, water flows so fast it doesn't dissapate heat properly. And it still functions enough to help regulate temps and faster warm up.

[d1mbu1b]

T-stat will restrict waterflow enough to let water cool engine. Without T-stat, water flows so fast it doesn't dissapate heat properly. And it still functions enough to help regulate temps and faster warm up.


That souds reasonable. thanks

Babbling below...

I wonder if its more applicable to closed cooling since the fresh water does not act like a heat sink and needs more time in the heat exchanger. Where in a raw water cooled engine the raw water can act more like a heat sink since there is an infinite supply thats always cold.

I am sure your right. Maybe free flowing water with little back pressure will not fill all the voids in the block completely. This means that the surface area for heat transfer is less and the mass of the heat sinc is less, both will reduce the amount of cooling.
I dont really see how velocity can affect the heat transfer.
(temperature decreases as pressure decreases, pressure decreases as velocity increases; ice falls off rockets when there launched, and wind chill effect)

I just installed an oil temperature gauge. I will experiment with this.
I figure the oil tempurature will give a better indication of the cooling systems ability.

[Cuda]

T-stat will restrict waterflow enough to let water cool engine. Without T-stat, water flows so fast it doesn't dissapate heat properly. And it still functions enough to help regulate temps and faster warm up.
I'm going to have to disagree here. Look at the water as one big heat sink, the cooler the water is, the more heat it will carry overboard. I think oil temp is more important than the water temp.

[BigGrizzly]

Two things. Cuda is correct on both counts. The thing with no t stat is, the way you state it, is a old wives tale. The real reason is the fast moving water creates a thermo barrier, like a pipe within a pipe. I am told that this also helps create steam pockets in some blocks. My suggestion is listen to Brownie. I have know him a long time and as of yet have never found him wrong. When he says I prefer, that means you should do it, when he says a must to me that means do it or pay the concquences.

[Barry Eller]

Two things. Cuda is correct on both counts. The thing with no t stat is, the way you state it, is a old wives tale. The real reason is the fast moving water creates a thermo barrier, like a pipe within a pipe. I am told that this also helps create steam pockets in some blocks. My suggestion is listen to Brownie. I have know him a long time and as of yet have never found him wrong. When he says I prefer, that means you should do it, when he says a must to me that means do it or pay the concquences.


Grizz, "Old Wives Tails" are OK in my book, on my third! I've always used T-stats, never killed a motor by overheating. Usually killed them by wearing them out!

:yes:

[geerbox]

I decided to go with crossovers and new t-stat housings after all of the information from everyone.
Thanks a bunch!
Does anyone have a picture of a drilled out thermostat, I think I better do it if Brownie says to...
What about the oil coolers, should I be worried with all of the rust in my system?

[gcarter]

Do you have any idea why you seem to have an extraordinary amount of rust in your engine? You obviously operate in fresh water in Nebraska, does the lake or river water have a low pH?
I would guess the water you boat in is very corrosive.
Any ideas?
If it is corrosive, and if you were to replace your engine, I'd consider closed cooling.

[geerbox]

I just bought the boat in the spring, for a good price...or so I thought. It has been in NY, GA, NC, those are the registrations I know of anyway. I think if I get it cleaned out good, I won't have to worry about it too much. I will periodically check things though

[gcarter]

I just bought the boat in the spring, for a good price...or so I thought. It has been in NY, GA, NC, those are the registrations I know of anyway. I think if I get it cleaned out good, I won't have to worry about it too much. I will periodically check things though
OK, all three of those states have a LOT of salt water.

[gcarter]

You might consider a flush with some acid.....maybe muriatic. It will definately dissolve a lot of rust and scale in your engine. It won't affect cast iron. You might try it for about 30 minutes and flush for another 30 minutes. You would want to disconnect your water pickup hose and remove the thermostat and anything else that's not iron. You would flush through the disconnected pickup hose. I don't htink you have anything to lose.
I'm not crazy, I'm in the water treatment business and using low pH is how you dissolve iron and put it into solution.

[Cuda]

Grizz, "Old Wives Tails" are OK in my book, on my third! I've always used T-stats, never killed a motor by overheating. Usually killed them by wearing them out!
:yes:
No, a t stat won't kill the motor, but keeping the water in the engine longer won't make it cool better. I remember arguing that point about t stats in cars. Some would try to say that a t stat keeps some water in the radiator, allowing it to be cooled longer. That may be true, but what do you think the water in the block is doing while that water is getting cooled. It's getting hotter, that's what.

[Barry Eller]

With holes drilled in the T-stat, water is moving, just at a more controlled flow rate.

[BigGrizzly]

Maybe you misunderstood. I always use Tstats. the wives tail is motors over heating because there is not one and the reason for it.

[d1mbu1b]

http://www.donzi.net/forums/showthread.php?t=47522

Coincidentally, the engine pictured in this thread shows a bypassless cooling system.

No circ pump, no bypass, no thermostat.
Looks nice, clean, and simple.

[gcarter]

http://www.donzi.net/forums/showthread.php?t=47522
Coincidentally, the engine pictured in this thread shows a bypassless cooling system.
No circ pump, no bypass, no thermostat.
Looks nice, clean, and simple.
That aluminum casting bolted to the front of the engine w/the water hose running to it is a bypass, i.e., it pypasses, or circumvents, a circulating pump.

[gcarter]

OK, my bad!

[mphatc]

Thermostats . . a few things seem to be getting missed here . .

They maintain a constant engine block temperature . . atleast they are supposed to

Holes are drilled in the top to maintain flow but most of all to bleed out air, as air pockets restrict water flow and a thermostat will not open unless it is submerged in water . .

As Brownie stated, an Alpha water pump is inadequete at idle to create enough water pressure or flow to push all the air through the bleed hole that should be in every thermostat . . and these need to be installed with the bleed hole at the top. Drilling a larger hole reduces the back pressure on the Alpha drive pump, allowing full water circualtion before the engine overheats. Restricting the risers ensures water is everywhere it needs to be.

Mercruiser 260 HP Alpha set ups come with a circulation pump . . for a reason. Service is easier with stock off the shelf components versus modified t-stats and welded risers . . .plus the pumps help to balance the flow to both sides of the V8. Cross over tubes, especially those where the inlet comes from one side, will not have a balanced flow.

In a marine application with fresh water cooling . .or sea water cooling a thermostat is still essential . . you do not want to inject 55 degree water into an engine at one end while it exits at 160- 180 some where else . .

Know that the block temperature at the inlet will barely rise above the inlet water temp, while the temp at the exit, or close to that will exceed 160, especially at the heads on top of the combustion chambers. This is not a good thermal equilibrium for the engine . . and can lead to headgasket failure . .especially with aluminum heads . . .


Gcarter, on your picture you show a crank driven pump. Please watch out for the front cover. The gasket is teflon or plastic, and when run at high rpms the pump will create enough pressure to push the gasket out. It is only clamped between two flat surfaces. I have the same pump, BTDT 2x and am now getting a cover made with an O-ring seal.

Mario

[gcarter]

I like the idea of the o-ring....are you having a groove cut into one side of it?
I've changed the impellor once and each time I've had it open, I changed the gasket. Right now I'm getting 1-2 gallons in the bilge every time I run it...maybe that's where it's coming from.

[gcarter]

Mario, can I interest you in getting two of them? The covers, that is.

[ALLAN BROWN]

The mission of the cooling system in a marine engine is is to keep the block at the CORRECT temperature. The word cool does not figure into the equation. The engine in your vehicle runs 200+ degrees at high output. They could make it run cold IF THEY WANTED TO. Clearances, evaporation and other factors make the engine want to be WARM. If you think that the mission is to run as cool as possible, you are waaaay off base. Some Gorilla motors have such a heat rejection problem (related to fuel consumption) that they keep all the obstructions out of the cooling path, and the BTU from burning 100 gallons per hour of gasoline keeps the motor warm. You must have seen the ads that claim that 75% of engine wear occurs at start up. When I worked for Tom Gentry on the "Gentry Eagle", We had to warm the 3600 HP MTU Diesels for 5 hours BEFORE WE COULD START THEM. Why do you think that was?

[CrackerJack]

We have a crossover with an alpha, and had to remove the t-stat. It runs in the summer around 180-190 depending on the speed. Today it was cooler out and it did not run as warm. It would probably need a t-stat if the temp. was cooler out.