Cooling system pressure - 454

[Artbaileyjr]

Hi all. New to the froum, old to boats.
I have a Volvo 270 drive with a 454 chev engine in a 25' day/cutty cruiser. I was wondering if anyone knows what kind of cooling system pressure I sould be looking for at about 3,500 RPM.

I am running a crankshaft driven raw water pump and a "V" belt driven marine style water pump. My problem is that the water is expelled by two 1/4" orfices into the exhaust flow (through the transom) which seems a tad small.

I'm not having any issues, but the cooling system is defenately NOT "out of the box". It was worked over by the previous owner before he blew the engine. (Didn't winterize it, then ran it with a broken cylinder wall until it threw a rod. NOT a pretty sight!) I replaced the engine, but also replaced the hoses on this kinda' Rube Goldburg cooling system.

I'd like to install a pee hole shooting aft and upward or a pressure gauge so I can see water flow from the helm.

Any help for this old timer would be helpful.

 

[Maclin]

Re: Cooling system pressure - 454

Can you post some pics of this? There should be a hose leading to each exhaust manifold, that water goes thru the manifold and up to the riser where it meets the exhaust. Your description of the 1/4 inch holes is confusing and pics would help immensely, thanks.

 

[Artbaileyjr]

Re: Cooling system pressure - 454

Thank you for your response.

In the above image, the raw water pump pumps water into the thermostat riser and subsequently into the belt driven pump for engine/thermostat use. The thermostat housing has a 3/4" hose connected to each side that run through each exhaust manifold (connected at the rear) and discharge at the front, where they tee together and also tee to two hoses (with a 1/4" orifice within each one) and exit into each side's exhaust via another exhaust casting which is bolted directly to the exhaust manifold. (Not sure what that casting is called) A 4" rubber hose then routes the waste water and exhaust to each exhaust port, exiting through the transom.

My other concern is frying the rubber exhaust connecting hoses if sufficient waste/cooling water is not present there. The exhaust ports are submerged when not under way. If one failed, the boat could swamp quickly, even though they have flaps on the exits.

So..... In as much as I can't see anything when I launch and start the engine, unless I run back and hang over the transom to look at the exhaust; THEN, I can't really tell because the water flow is so small at idle, I'd like another method of having a visual indicator of raw water pump function, and of course, system pressure when under way. (That's why I was thinking of a pee hole, like an outboard or personal watercraft)

I was thinking of adding a tee between the existing tees and using a pressure gauge at the helm, or as I said, a small hose connected to an orifice pointing upward and aft from the transom, so I could see at a glance if I have water pressure and how much, as judged by its height or flow.

I just have no idea what pressure would be appropriate or correct on this system.

As I said before, the engine runs cool. The above image was taken as I was installing the replacement engine, so there were still come loose ends at the time, but the cooling system is as it is today . So far it has about ten hours on it and I haven't ventured too far from shore until these nagging little issues are clear in my mind, and I'm completely comfortable with it's safety and dependability.

Any input is much appreciated.

Art

 

[Don S]

Re: Cooling system pressure - 454

Where are the risers. How do you plan on keeping water out of the engine?

 

[Artbaileyjr]

Re: Cooling system pressure - 454

Where are the risers. How do you plan on keeping water out of the engine?

Yah... You'd think, huh?
It really doesn't have much of a riser. The casting at the rear of the exhaust manifold is the riser, but not quite what you'd see on a Merc or OMC setup. That's simply what was on it when it came into my hands.

The manifolds hang below the exhaust ports and the risers are short, but it all seems to work without hydroing. <shrug>

The exhaust(s) are right below the swim plank, ..... maybe 50% submerged. That puts the risers above the waterline and the manifolds fall aft, so unless you took some serious water, they will still drain, but without exhaust flaps, if you were shut down and took a good swell from the rear, I think you could be in trouble. There were also 5 people in the rear seat of the boat having lunch when the above image was shot. A rare occurrence for it to sit that low, but certainly possible, as the image attests to! All tolled, I'd venture a guess that there is 10" - 12" fall from the manifolds to the transom exhaust ports. The mere fact that it has been on and off of the water a number of times without incident tends to indicate that the cylinder(s) with the open exhaust valve(s) stay empty!

Someone did some weird stuff with this boat. The drive is a NEW replacement, but the engine was a beater (and blown up). There is also a BOOST gauge in the dash that was added at one time, so somewhere along the line, someone had a blower or turbo back there. All the documents show it as a 454, as the same boat shop/broker/storage has handled the boat since new. I guess the guy had four or five boats that he liked to play with, and he died so the kids blew this one up, stored it with the same broker, and then after years of asking way too much for it, dumped it for peanuts. That's how I wound up with it.

I also have many unanswered questions. I'll just take them one at a time. For now, I'm interested in the cooling system. Soon, the only liquid in it will be antifreeze and it will be tucked away for the long, cold, Idaho, high country winter. <sigh>

Art

 

[Maclin]

Re: Cooling system pressure - 454

That is a pretty amazing one-off setup there Art, maybe 2 or 3 "off"! Maybe those orifices act like jets, I have no idea why flow would need to slow down right there though. Looks like a really neat boat though, good luck.

 

[Artbaileyjr]

Re: Cooling system pressure - 454

Well; The only thing that comes to mind is that an orifice would create back pressure and assure that each side will receive equal flow into the exhaust stream. That's the reason that I'm trying to get to the bottom line of what the normal engine cooling system pressure would be if it were say,... a Mercury stern drive? An OMC stern drive with a small block Chevy? Lets just say: Any I/O V8 with a crankshaft driven Sierra raw water pump.

If I have some idea of what a "normal" system operates at, then I can modify mine to flow as much as possible through the exhaust but still have proper or "normal" cooling system pressure. Also. flowing a maximum "safe" pressure will be easier on the raw water pump as there has got to be a sh**pile of back pressure on the raw water pump when running at high RPM's.

Thank you for the help thus far. Much appreciated.
Art