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318 right side is hot

D

dcpaxton

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"I've got a '69 Centur

"I've got a '69 Century Resorter with a lm318. I recently had the entire motor overhauled...got it back from the machine shop....put it in the boat...took it to the lake.

After I finally got the boat started, I ran it for a while to make sure the engine cooled properly. The engine did cool, but the manifold on the right side (driver side) got extremely hot.

Since then I have put new impellers in the pump and also replaced the tube inside of the manifold...neither fixed the problem. The manifold still gets extremely hot. Right side only...the left is cool.

I am frustrated! Any suggestions would be greatly appreciated.

Daymond"
 
"My guess is that the exhaust

"My guess is that the exhaust riser is plugged with some debris. Are you getting good exhaust water flow out of the pipe on the hot side? Mine was similar and I found chunks of rust, chunks of rubber impeller parts, etc. Clean those out and get some flow and you should be all set."
 
"Andy's right; there's

"Andy's right; there's an obstruction in there somewhere. In addition to checking the riser, check the water flow entering the manifold. If you're set-up's like mine, the raw water flowing to the right side manifold passes through the transmission oil cooler first. Possibly a chunk broken off the rubber raw water impeller may be blocking the flow.

Let us know what you find..."
 
"That's just what I though

"That's just what I thought...I pulled the manifold and the riser and took them both to the machine shop to be cleaned.

After cleaning, I put them both back on just knowing that this fixed the problem....NOPE...Still getting hot on the right side.

I installed a clear hose coming out of the tranny cooler to the riser so that i could observe the water flow...it seems to be flowing pretty good.

The water is not makeing it up the manifold all of the way. The lower half of the manifold is cool to touch while the upper half is extremely hot....could it be that there is not enough water pressure to push it all the way up the tube?

I just don't know what to try next."
 
"I'd start at the beginnin

"I'd start at the beginning. Check water inlet in the hull to be sure it is clear of obstructions. Check the seawater strainer. Double-check that the impeller rubber blades are trailing the direction of rotation. Pull all heater hoses and check for obstructions. Lastly, is the water distribution tube installed in the correct end of the manifold? The tube installs from the riser end and the manifold. Manifold water inlet should be at the rear bottom of the manifold. Front end of the manifold should have a solid plate on it. That config. forces the cooling water to travel the full length of the manifold before exiting. If the distribution tube is installed incorrectly the water will short-circuit in the manifold and cause very uneven cooling."
 
"If it still running hot on th

"If it still running hot on the top of the manifold, try running without the brass tube. This would also give you the opportunity to check the inside of the manifold water jacket for obstructions."
 
What is a "seawater strain

What is a "seawater strainer?" Where is it located? Does a fresh water system even have one? I heard this lingo in other discussions.

I do have the tube installed as you mentioned.

What are your opinions/experiences in running with/without the brass tube?
 
"Seawater strainer is a screen

"Seawater strainer is a screen filter assembly, separate from the engine, which strains out debris your raw water pickup may injest. It's probably located near the valve (seacock) in your hull where the raw water enters. You may or may not have a strainer in your boat. Mine didn't when I bought it.

Yes, your engine uses raw water to cool the closed system fresh water coolant in your engine.

Where does the cooling water enter your manifold? With a water distibution tube installed, it should enter from the riser end of the manifold, at the bottom. I'd pull the water dist. tube out like Chris said and see if that has an effect on the cooling.

Did you have any cooling problems with that manifold before the engine was rebuilt? If not, and your water hookups are now still exactly the same, I'd go back to Andy's diagnosis... there's a blockage in there somewhere.

Last thing, do you have dual exhaust pipes at the stern? If so, do equal amounts of water discharge from both pipes?"
 
"I accidentally left out the w

"I accidentally left out the water tube on mine and it runs cooler that way. The water enters mine in the FRONT, goes through and comes out the back. Next time I have the other manifolds off, I'll leave the water tube out of them as well.

Jeff"
 
"In a standard in-line arangem

"In a standard in-line arangement, the front of the manifold is the highest point. The tube extends the outlet to near the highest point in order to draw out any air from steam or from the raw water intakes. What's confusing about Jeff's, mine and several other small block configurations is that in ours, the water enters the manifold from the front. It would seem to short circuit the water flow. The diagrams I have seen call for the water to enter the low point of the manifold and to be drawn out through the tube near the high point."
 
"Peter is correct. I had a li

"Peter is correct. I had a lively argument with an OSCO tech rep on that subject--he insisted there was NO WAY it would work! (It does, though, even with that fool tube in there.)

Jeff"
 
"I'm going to chime in wit

"I'm going to chime in with my 2 cents worth..If the manifold is fed from the lowest point ( the underside) & the tube has been replaced,& the water flow to the manifold is good, the only thing I can think of is the gasket between the manifold & riser, its either worn out or has been broken, & is letting the water out to fast before it has a chance to absorb the heat, its only supposed to have 1 hole in it at the top."
 
"I encountered this same probl

"I encountered this same problem last year, after replacing the manifolds,water pump, hoses,back flushing by pulling freeze plugs. I was able to fix the problem by pulling the thermostat out and reducing the flow of the return or bypass hose with a clamp. Now I need to determine if my thermostat is not opening enough or if the rubber seal in the housing is to worn."
 
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