460 ford runs cold

[grumpy old man]

I recently purchased a '79 Tarva open bow with a 460 ford and a Berkley pump. The engine runs stone cold. I have checked the temp gauge by unscrewing the sender and putting it in a can with water. When I heat the water with a thermometer in it the temp gauge on the dash reads approxiately the same as the thermometer so it is not a gauge problem. The way it is presently plumbed the water picks up at the jet drive, a fitting on the inboard side of the transom. It goes directly to the water pump block off plate into both sides of the engine. It exits at the water outlet housing on the intake manifold and discharges into the exhaust manifolds just below the front exhaust port. I tried putting a restrictor plate under the outlet housing with 2 5/16 in holes in it. Now when idling in the no wake zone it will heat up to about 135 but as soon as you give it any throttle it will drop back down to the cold peg. What limited boat mechanical experience I have had has been on v drive setups, this is the first jet boat I have worked on. Any help? I can not believe that this thing is supposed to run this cold as it is hard on an engine for many reasons. Thanks in advance for any help offered, the grump

 

[mkast]

Re: 460 ford runs cold

Is there a thermostat in this application?

 

[grumpy old man]

Re: 460 ford runs cold

Been out of town for near a week and away from the computer but no thermostat, in fact the "thermostat housing" has a rib cast in to it which makes it impossible to install a thermostat. If you think about it it makes sense because the engine partially drains every time you shut it off and it would air lock everytime you restarted it if it had a thermostat. Most of my boat experience has been with hot boats, dry stacks and the like, but I seem to remember that the point of wet manifolds was to run the intake water through them to preheat the water before it hits the engine. These apparently do not do that so I am at a loss as to why even go to the trouble of putting them on. I did e mail Hardin marine because it is a Hardin setup with their serial number on it and I must say that I am quite unimpressed with their lack of response.

 

[RogersJetboat454]

Re: 460 ford runs cold

Read this, it may help;

http://www.performancejet.com/ttjetboatenginecooling.html

Pretty sure I emailed the guy that owns that site a few years back about setting up a cooling system. He was happy to give me his 2?.

 

[grumpy old man]

Re: 460 ford runs cold

I checked out the website and found the article on jet boat cooling. Apparently my problem is common. In addition to the normal problems mine is plumbed wrong because it does not go through the exhaust manifolds for pre heat, and I am not sure that these manifolds have that capability. Unfortunately I can't just run out and check them because the boat is at the lake house two hours away. I e-mailed them to get their input and am hopeful that they can help. Thanks a bunch for the information. I guess that I will be able to add jet boat plumbing to my resume when I am done.

 

[HT32BSX115]

Re: 460 ford runs cold

Howdy,

I suppose I am gonna show my ignorance of this so please bear with me......

It's clear that the "jet people" have devised a seemingly un-complicated plumbing setup ( that eliminates the circulating pump)......... I am just not getting the reason why someone wouldn't use the standard cooling method used by Mercury, OMC, Volvo etc. (that works)

That is, using a "regular" automotive-type pump that moves or circulates coolant (water) into the block, then up into the heads exiting through the T-stat housing and/or back into the pump.......having the t-stat allow *some* measured amount of cold water into the block to maintain some sort of desired temp.

There's evidently no "RAW-WATER" pump required, since the jet pump can provide raw water in any amount needed.....


So my question is why not do it they way that works? I.E. Use a circulating pump and a t-stat, and let the water that bypasses the t-stat (and hot water from the engine/heads) go to the exhaust manifolds and risers?


I am clearly missing something here........

 

[grumpy old man]

Re: 460 ford runs cold

The only thing that I can figure out is that they were attempting to keep it simple. Admittedly using a heat exchanger to replace the radiator and maintaining the automotive cooling system is by far a more desirable system. It was well engineered and quite reliable. Apparently they chose to eliminate a lot of moving parts, plumbing etc and just use the pressure off of the jet to move the water. The problem in this case is that after talking to Performance Jet keeping it simple did not work. Apparently the problem with feeding it off of the jet drive is the pressures created. If you think about it the nozzle pressure on the jet drive must be tremendous, James was speaking in terms of up to 200 psi. This kind of potential pressure makes it impossible to restrict the cooling water so you have a water flow through the cooling system that approximates your garden hose at full open. That kind of flow through the cooling system with water straight off of the lake with out even pre-heating it makes for a stone cold engine. Not a good thing in anyones book. He has engineered a pressure relief bypass which maintains a steady 12 psi in the cooling system making it possible to restrict water flow and install a thermostat to maintain an acceptable engine temperature. Unfortunately I need to check some things on my wet manifolds before I can proceed and the boat is at the lake house two hours away. I will within the next couple of months get the cooling system fixed and if anyone is interested will post the results when done. the grump

 

[HT32BSX115]

Re: 460 ford runs cold

This kind of potential pressure makes it impossible to restrict the cooling water so you have a water flow through the cooling system that approximates your garden hose at full open.

Well,

That's not as hard as you might think..... There are simple water pressure regulators that will throttle it down to whatever pressure/flow you need.....if you were going to use an off-the-shelf regulator, you would probably need a "sea-strainer" to keep and debris out of the regulator.

I can see that jetboat cooling systems "want" to be fairly simple but you do need to slow the flow to properly cool any engine.

A raw water cooling system is not that difficult to make work and that type of system is the most common in any inboard or I/O marine engine......but BOTH systems use a circulating pump, thermostat and have discharge cooling water from the both the raw-water pump and that amount that is ported to the block/heads eventually ALL going out through the manifolds and risers.

The flow through the block and heads is "throttled" by the t-stat. The (bypass) flow through the manifolds and risers is not throttled for the most part. (although some T-stat housings have check balls and/or specific sized ports to control "splitting" flow between the manifolds and risers.....

Take a look at Mercruisers water flow diagrams for raw water cooled BBC engines and you'll see what I mean.

Your engine will of course run best if the temp maintained at around 180* or so. If it doesn't completely warm up you end up with water vapor condensing in the oil, and incomplete combustion etc...... (I'm sure you know this)


Cheers,


Rick

 

[grumpy old man]

Re: 460 ford runs cold

Yes, James makes a bypass regulator that maintains a constant 12 psi going into the engine by dumping anything over that 12 psi directly back into the lake. The other problem with the jet applications is that unlike an outdrive application which uses a small water pump to supply the water, the nozzle pressure varies dramatically depending on the throttle opening, and because of that wide range the regulator needs to be specific to the application. The greater the throttle opening the greater the pressure at the discharge nozzle and the greater the pressure and flow into the engine. The very first step is to control the supply and remove that variable. Right now I need to check the wet manifolds to see if it is possible to run the water through them. Apparently on the early Hardin manifolds not all the wet manifolds with the center discharge riser could be plummbed to pre-heat the water. Unfortunately I can not just run out and check because the boat is presently at the lake house which is a 4 hour round trip (and $4 a gallon gas) away. So the whole thing is on hold until the next time we go up and I can check the manifolds. As far as the engine temp thing, I grew up in my fathers auto repair shop and am quite familiar with the problems of running an engine cold. That is why this has become an issue. Personally I like to see them up around 200 degrees. I found it amazing how the crankcase sludge diminished as engine temperatures rose because of emission requirements. Engine life rose accordingly, granted the improvements in oil and metallurgy also enter into the picture but burning out the combustion byproducts in the oil was, in my opinion, the biggest step because you can filter out the solids but not the acidic by products.

 

[HT32BSX115]

Re: 460 ford runs cold

Right now I need to check the wet manifolds to see if it is possible to run the water through them. Apparently on the early Hardin manifolds not all the wet manifolds with the center discharge riser could be plummbed to pre-heat the water.

I am not getting why you 'd want to pre-heat the water.....(and depending on how fast the water goes through the manifolds it wouldn't preheat much anyway......)

It doesn't matter what temp the water is going onto the manifolds and/or risers. If you have a thermostat controlled cooling system for the engine and a circulating pump the engine temp is controlled by allowing water to enter the engine in controlled amounts (by the t-stat "throttling" the water that exits the engine). any additional water is just bypassed to the manifolds and risers and over board.


Maybe I am missing something(I'm just thinking out loud).....I think I could adapt a standard plumbing regulator (with a sea-strainer) to provide 15-20psi raw water from the jet pump supply for the engine. I don't think it would matter what the supply pressure is (the regulators I found are good up to 300psi)


Where do you keep your boat?

 

[grumpy old man]

Re: 460 ford runs cold

I believe what you are missing is that the water supply on a jet boat is much more difficult to control than I believe you realize, and ALL of the water is going through the engine. On an IO setup you have a small water pump that was designed to supply the water for cooling that specific engine, and the factory water pump is circulating most of the water in the engine in the same manner as it is circulated in an automobile. on my old OMC there was a casting that the lake water went in and out of and SOME of that water was routed into the engine. Just how it was internally ducted I have no idea but only a small portion of the intake water went through the engine, most of the water in the engine kept circulating maintaining a reasonably constant temperature. I will have to say that a great deal more engineering and thought went into the system than the jet people put into theirs. On a jet boat they are attempting to siphon off a controlled amount of water off of a LARGE fire hose. I do not believe that a standard plumbing regulator could be used because in my experience as a building contractor and inspector I would doubt that it could be adjusted down to the 12 psi range, particularly when on the average jet the incoming supply can vary from almost zero pressure idling around the marina to well over 100 psi at normal crusing speeds. Ultimately with a bypass regulator which will bypass most of the water off before it hits the wet manifolds the water supply can be slowed down to a constant controlled amount. As for the wet manifolds pre heating the water, you must take into account that without pre heating the water the stone cold lake water is entering the engine and even with a thermost, which the system will ultimately have, the block which gets the cold water first will be lake cold and the futher up the engine you get the warmer the system will be. In other words the block will be fairly cold and the heads will be normal operating temperature. An improvement but still not the answer. Utilizing the original water pump and a semi closed system is obviously the better option but I would need to come up with a system similar to the one on the OMC, or probably any other IO, that has the ability to use only the amount of cold water necessary to keep the temperature constant or even better a heat exchanger which would allow the engine cooling system to be closed. As I am not particularly interested in re-engineering the entire system I am reduced in options to working with James at performance jet to modify the existing system and making it at least workable. With twenty plus years of experience working on this problem he has thought out the problems far more than you or I. For the most part I am regurgitating partially digested information I have received from him but as I work on it it makes sense.
As for the boat's home it is at Lake Arrowhead in So. Cal. in the summer and in the side yard in Oak Park, just west of Los Angles, in the winter. Seeing two feet of snow on the ski boat was more than I could handle so I tow it up in the spring and down before winter.