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early mercruiser closed cooling system

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fullbull315

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Hello, I'm new to this forum. I just bought an older boat with twin mercruiser 270s with closed cooling. This is an interesting looking cooling system; it appears that the reservoir is an aluminum casting that sits on the rear of the engine and connects directly to the exhaust manifolds. I was wondering if anyone had any pictures of this type of closed cooling system assembled, or any flow/assembly type drawings.

I got the seloc manual which doesn't seem to have anything specific to this system, and have seen some exploded diagrams of the system, but am still having a hard time picturing the entire system put together on the engine. The weirdest thing on this is that there seems to be a hole in the bottom of the reservoir and i can't figure out where that should go. thanks for any help.
 
I agree...... pictures would help greatly!

I am thinking that what you were calling a "reservoir" … is actually the "heat exchanger".

The lower-most and larger heat exchanger port is typically for the coolant supply to the engine's Circulating Pump ( aka water pump).
There will also be a slightly smaller lower port for the seawater supply.

Depending on whether this is a "half system" or a "full system", the coolant routing/hoses will vary.

The spent seawater leaving the heat exchanger will always be ported equally to the exhaust elbows.

Again, pictures would be very helpful.


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aluminum casting that sits on the rear of the engine and connects directly to the exhaust manifolds.

Why does it sound like the 470 motor 270/470????
Untitled47_zps27c2f1dd.jpg
 
Thanks for the feedback so far.

The engine is a mercruiser 270, which is a Chevrolet 350 block that was originally rated at 270 HP. I believe that it is basically the same engine as the mercruiser 260 from the same era, only for inboard use instead of sterndrive.

The engine serial number is 3077477, and one engine ends in L, the other in R, which I assume refers to the rotation. I believe that the engine is a 1971, which is consistent with the serial number as far as I can tell.

The long block was re manufactured by Jasper, I can look in the spark plugs and see that they are .040 over pistons, and brand new with no carbon at all, never been fired.

I have attached a photo of the main components that I have. I originally described this incorrectly, the reservoir will sit a the front of the engine, and attaches directly to the front of the exhaust manifolds. I have taken the picture with the system in the rough layout that I think that this is supposed to look like.


cooling rough layout.jpgmercruiser serial number.jpg
 
OK.... if these are I/B GM V-8s, that would explain the closed cooling systems not being quite the same as the I/O systems.

If you are going to replace the old "log" style exhaust manifolds, I'd strongly encourage you to go with a more modern centerise style, and make any modifications to the Closed Cooling system as needed.... unless for some reason you must use the log style.

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I'm not really interested in replacing these manifolds or updating the closed cooling system, I'm really just trying to figure out how to hook it up correctly.

The engines are currently just long blocks, with none of the accessories installed, and none of the hoses hooked up. I'm honestly not sure which hoses are present and which are not, so I don't really feel comfortable just bolting everything up and trying to line up the hoses, I'd like to have a diagram, or preferably some pictures.

I found a diagram on boatinfo.no in the mercruiser volume 1 tech book, and I found some exploded diagrams on marineengine.com under accessories, but they don't seem to match up quite the same. I'm still looking trying to compare; it seems that this system is quite rare.
 
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