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    I'm No Expert Shaun's Avatar
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    Default tstat

    I'm trying to understand why a special tstat housing is needed to run one in a boat. The only think i can think of is that a tstat would cause problems with a wet header system using a pressure valve since the tstat would cause pressure differences. For example at idle on a cold motor if the tstat was closed the pressure would go up and cause the basset valve to open... Is this the case? If so, do you dry header/bander guys run a tstat?

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    TEN THIRTY ONE RCB19's Avatar
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    Quote Originally Posted by Shaun View Post
    I'm trying to understand why a special tstat housing is needed to run one in a boat. The only think i can think of is that a tstat would cause problems with a wet header system using a pressure valve since the tstat would cause pressure differences. For example at idle on a cold motor if the tstat was closed the pressure would go up and cause the basset valve to open... Is this the case? If so, do you dry header/bander guys run a tstat?
    Sounds as if you already have it figured out. I don't know of anyone that runs a t-stat in a jet boat even though they are available. If your motor was built correctly (clearances) you dont need to worry about keeping regulated heat in the motor.
    RCB

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    I'm No Expert Shaun's Avatar
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    Quote Originally Posted by RCB19 View Post
    Sounds as if you already have it figured out. I don't know of anyone that runs a t-stat in a jet boat even though they are available. If your motor was built correctly (clearances) you dont need to worry about keeping regulated heat in the motor.
    I've always been told it's important for a engine to run at the temp it was designed to run at. Seams like running a tstat would be ideal to keep the motor running at a consistent temp, rather then moving around a bunch?

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    Senior Member GT Jets's Avatar
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    The reason for the four hole stat housings is so the water never stops (no water pump), the housing acts like a bypass and a flow regulator, the water through the block never actually stops, whereas the regular housing completely block flow, the other reason is like you said, for the exhaust coolin, I guess if you were running dry exhaust, you could just drill a small hole in the stat and use a standard housing, but the water pressure would have to regulated to be a very consistant pressure, otherwise it would be all over the place as far as temp, the "special" housings allow for the stat to be pushed off its seat to prevent this from happening.

    On the race boats, we just run a water pressure regulator on the inlet water (typically set for 12#), then a thermostatically controlled oil cooler (we sometimes run in 50* water) set for 195*F oil, let her rip, for hours at a time I might add...

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    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    I'm No Expert Shaun's Avatar
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    I read somthing once about drilling a small hole in the tstat. I figured this was just to release air since it's not a closed system but now thinking about it, the water down in the block/heads may be a different temp than the water sitting up by the stat since there's no way for it to continually move around, that seams like a bad thing to me. I run a pressure regulator thats set at 25-30 PSI at WOT, wonder if drilling a few holes in a tstat would allow enough water to move so that the stat could sense the right temp to open but not enough so that the water actually heats up...

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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by Shaun View Post
    I read somthing once about drilling a small hole in the tstat. I figured this was just to release air since it's not a closed system but now thinking about it, the water down in the block/heads may be a different temp than the water sitting up by the stat since there's no way for it to continually move around, that seams like a bad thing to me. I run a pressure regulator thats set at 25-30 PSI at WOT, wonder if drilling a few holes in a tstat would allow enough water to move so that the stat could sense the right temp to open but not enough so that the water actually heats up...
    FWIW, I think your playing with fire with that much water pressure, we used to run a BBC at 30# and it blew a welsh plug (freeze plug) out of the block, an automotive engine only runs at 14#, just a thought.

    Another way to achieve temp control is a thermostatic bypass, remote bulb on the engine and just bypass what it don't need to cool, just a wild out loud thought...

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    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    I'm No Expert Shaun's Avatar
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    Hmm, i was told i want to see 25# at WOT to help prevent steam pockets.

    Curious, you other guys who run pressure guages, how much pressure are you running at WOT?

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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by Shaun View Post
    Hmm, i was told i want to see 25# at WOT to help prevent steam pockets.

    Curious, you other guys who run pressure guages, how much pressure are you running at WOT?
    If you run two water lines from the rear water ports of the intake manifold to the exit tee, steam pockets are never going to happen, the lower water pressure will also translate to slower water travel and increase the thermal coefficient increasing temperature control...Just my .02c

    The water flow in most Chevys suck as far as balance from the front of the motor to the rear, which is why I think most engine failures seem to be at the rear of the motor (I've puked cyl. 7-8 five times more than 1-2) and 7-8 get the most oil...Just my humble opinion...

    I would rather see the water go in the front (Factory) and out the back, it's gotta be closer...we used to run the inlet water in throught the drain holes in the block and out the four corners of the intake, seemed pretty consistant.

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    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    I'm No Expert Shaun's Avatar
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    Scott (Steelcomp) ran his through the bottom of the block but i think his exits where out the tstat area of the manifold. I've though about tapping the back of the manifold after seeing bob's (gn7's) manifold and his setup. My idea was to tap the back on each side and then run a hard line up to the tstat housing which would also be tapped, that should eliminate any air pockets back there... so i would think.

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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by Shaun View Post
    Scott (Steelcomp) ran his through the bottom of the block but i think his exits where out the tstat area of the manifold. I've though about tapping the back of the manifold after seeing bob's (gn7's) manifold and his setup. My idea was to tap the back on each side and then run a hard line up to the tstat housing which would also be tapped, that should eliminate any air pockets back there... so i would think.
    It works well and evens out the cylinder temps (looks badass too), We just used some AN fittings and hose...Backwoods, but works.

    GT
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    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    Sit N' Spin Jetaholic's Avatar
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    This was a thread I posted on another board.

    The t-stat kit is made to be used with a different type of cooling system called a LPHV (low pressure high volume) cooling system.

    You've probably noticed on a lot of jet boats how the engine temperature fluctuates with pump speed, similar to how your engine temp in your car would do if it were low on coolant. This is because the water is restricted by an adjustable gate valve between the pump and the engine. The reason for that is to keep the pump from overpressuring the block, which would otherwise blow gaskets and get water in the oil. But while limiting the pressure, it also limits the water volume (the actual amount of water) that can get to the engine. Because of this, at an idle there isn't enough water to completely fill the engine block, causing the temperature to rise at the slower pump speed. As the speed of the motor and pump are increased, more water can now get to the engine, cooling it back down.

    The idea is to run the water fully on. Now with it set this way the pump can and will overpressure the block. To prevent that from happening, you run a bypass pressure relief on the inlet of the pump. You can get them at McMaster-Carr...http://www.mcmaster.com and they sell for about $50. Their part number is 9763K12 and it's the one that's rated for 0-300psi. They're adjustable and you want to set them with air so that it's just starting to open at 12psi. With the large volume of water that the pump kicks out when unrestricted, any excess water that causes the block pressure to build past 12psi will be dumped overboard. You then run 2 overboard dumps. If your headers are using one of your overboard dump connections, this will need to be removed as this connection will need to be ran to an overboard dump fitting. The header water will be tapped from another source.

    By not restricting water to the block, there will be plenty of water to completely fill the block, eliminating the possibility of hot spots in the heads.

    So now you have full unrestricted water flowing from the pump, the block is always completely full of water, and your engine water pressure is perfect regardless of pump speed. So far so good right? However, with this setup the engine will run far too cold. We need a way to boost the engine temp up to 140 or so for proper combustion to take place. This is where the thermostat kit comes in. It's job is to provide a means of raising the engine temperature without restricting water flow between the engine and the pump.

    Now you have perfect block pressure and since the block is always full of water regardless of pump speed, you now have a constant running temperature of 140* - 160* with no water in the oil.

    Now for header equipped boats...we need to bring the header water in from another source. You'll need a gate valve between the Bassett T-valve and whatever water source you decide to tap off of. You can T off of the water coming from the pump, or you can even remove one of the pipe plugs from the intake manifold water crossover and tap it from there. This way, opening the gate valve sends more water to the headers and has no effect on block pressure. Again...no water in the oil.

    Now some people think that when the thermostat opens that ALL of the hot water dumps out and ALL NEW cold water fills the block. This is not the case. It TRICKLES some of the hot water out and as some hot water exits, some cold water enters to displace the amount of hot water that exited. Once there's enough cold water to cool the hot water that's still in the block down a few degrees the thermostat closes again. Eventually the whole system balances out and the thermo just stays open just enough to keep the water temp at the temp that the thermo is staying slightly open at. But basically there is very little water flow through the block with this type of system.

    As far as it causing issues with the T-valve in regards to pressure, I have my T valve plumbed right off the intake manifold water crossover with a gate valve in line with the T-valve and my water turns on and off when it's supposed to and all I have is steam...no water droplets coming out of the headers at all.

    I've run this system and have had absolutely no issues with cooling or water in the oil or getting my headers to steam properly. The engine runs at a constant temperature everytime regardless of pump speed or lake water temp. My motor broke in October due to a valve train issue that I think had a lot to do with improper valve train geometry. Upon teardown there wasn't even the slightest hiint of any water anywhere in the oil. Not even on the valve covers that some refer to as condensation. Absolutely no water whatsoever in the oil at all.

    Me personally...I wouldn't plumb a jet boat any other way. In my mind this system makes perfect sense and why would I want to run it any other way?

    Hope this helps.
    Last edited by Jetaholic; 12-28-2008 at 10:44 PM.



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    Senior Member GT Jets's Avatar
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    Jetaholic, that's good stuff right there, very similar to what we use....Thanks for posting, I feel less like an alien now

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    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    TEN THIRTY ONE RCB19's Avatar
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    Quote Originally Posted by Shaun View Post
    I've always been told it's important for a engine to run at the temp it was designed to run at. Seams like running a tstat would be ideal to keep the motor running at a consistent temp, rather then moving around a bunch?
    Most of the guys that i know are all trying to keep the temps as low as possible including myself due to engine requirements. Inlet pressure is regulated to 25#'s. Don't be fooled by what your temp gauge tells you on the dash. The numbers that you are seeing are merely what the water is absorbing from the engine before it is dumped overboard (Open cooling system). True engine temp is generally higher than what your gauge is telling you. Thats why we aim for the cool side knowing that the true temp is most likely 10-20 degrees higher that what your gauge is telling you.
    Last edited by RCB19; 12-28-2008 at 11:19 PM.
    RCB

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    Senior Member Futs's Avatar
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    Quote Originally Posted by RCB19 View Post
    Most of the guys that i know are all trying to keep the temps as low as possible including myself due to engine requirements. Inlet pressure is regulated to 25#'s. Don't be fooled by what your temp gauge tells you on the dash. The numbers that you are seeing are merely what the water is absorbing from the engine since it is an open cooling system. True engine temp is generally higher than what your gauge it telling you. Thats why we aim for the cool side knowing that the true temp is most likely 10-20 degrees higher that what your gauge is telling you.
    Word!!!

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