93 5.0l cobra overheating

[shayne23]

Exhaust manifold starboard side lets water out at idle but once u start moving water stops flowing on the one side causing manifold to overheat. Is this a bad manifold or riser. Anyone pls help...............

[shayne23]

someone pls help.

[bilgeboy]

I’d like to help you think through this problem. I am really only familiar with fresh water cooled diesels that exchange heat with raw water, though.

I might learn something here as well.

You have a single raw water pickup and single raw water pump? Is that right? But as I understand it, you have twin exhaust manifolds, and as the boat picks up speed, you only exhaust raw water out one manifold. Where does the water from the pump split into two separate circuits?

Maybe we can get you started in diagnosing this problem.

Mike

[shayne23]

there is a y split. there is a hose coming from the water pump that goes into the y spliter from there it goes into each side manifold took that off and it spits water fine. noticed today when started very little water is comeing out of the one side even at idle. suppose it must be the manifold or riser. hate to replace it and still have the problem though. must be clogged and gettting worse as more pressure is push through it. do i just replace the one or do them both and hope thats it for a while? what do u think.

[bilgeboy]

OK, I've got it.

Interesting problem. Honestly, I thought you might be a bit nutty after reading that the problem is worse when you throttle it up, but I gave it some thought, and not only do I think you are sane, but that you also might be lucky!

Its clear that the riser and manifold have to come off. That is for sure. What a great project.

So they come off with the normal amount of difficulty and you inspect them. Worst case scenario is you need new ones. Depending on age, climate and usage patterns, you've got to get new ones every so many years, so give it some thought. Better, and even quite possible, is that the offending congestion in the plumbing is accessable and can be removed with a flat head screwdriver and some gentle elbow grease. You might "hot tank" or acid dip them, yourself or at the local radiator shop, paint them up and you can squeeze another few seasons out of them.

Why do I think you might not be nutty? You have the plumbing equivalent of a "chinese finger trap." I guess you are thinking the same thing. You have a bunch of loose debris that is trapped in the system, and the greater the output of the raw water pump, the more tightly packed together this debris gets, making it more difficult for water to pass through.

Just a thought, but we both know they have to come off, so please do this, and post some pics for us all to enjoy, and we will have our answer soon.

Good Luck, Shayne

Mike

[shayne23]

i change the riser and manifold. opppppps forgot to drain water out of riser before taking off. water got into manifold now wont start. still cranks over. need help

[bilgeboy]

Stuff like that happens. I'll say again that I am an oil burner, don't know too much about gas. By the looks of this thread, you can't be too choosey, though!

I can't imagine you got enough water in there to really muck things up. Its a good sign that it cranks over, and you probably want to keep doing that for a bit.

Maybe you should remove the plugs before any further cranking attempts. A few reasons I can think of to do this

1- It will prevent damage on the compression stroke if there is ALOT of water in there.
2- You can spray a bit of fogging oil in to prevent seizure. This is probably the biggest threat.
3- It will allow an easier escape for water vapor if there is any in there.
4- You can clean up the plugs or replace with new ones.

I really can't see that there was that much water in your riser to do much harm. But I guess I would pull the plugs, crank for a while without smoking the starter, put new plugs in and check for spark and fuel. It should be good to go.

Good Luck,

Mike

[gonzo]

Did you dry all the water off, specially if it was saltwater? Some of the Y exhaust pipes have flappers that jam and cause that problem.