Water from one side..?

[frustratedboater]

All,
I have an 85' Mastercraft w/Chevy 350 (replaced the 351), direct drive, with the PCM manifolds. I am experiencing exhaust flow from only the right side manifold. The water is 50-60lbs pressure at the hose, so i know there is plenty of water. During the normal season I had a little flow out the left side, but not as much as the right side, which seems to pour out. I just started it from a 3-4 week sit and I'm not getting anthing out from the left exhaust side.

During the summer, while experiencing the little flow, I split the top of the manifold off to take a peek and it looked fine. No visable signs of rust. I even sprayed water all through it to check if the top piece flowed well and it did. The two side water lines, coming off the thermostat, are pumping out water, so the manifolds are getting water at the source. I pulled out all the petcocks from either side and I am getting water flowing through the bottom half of the manifold! Very strange...

I did notice that the through hull water pickup had a vaccume suction (sucking the cup to the hull) to it--I did not have that before. Is it possible that the block has rust build up at the manifold preventing it from coming through?

Please, any suggestions to my lack of water?

~FB~

 

[HT32BSX115]

Re: Water from one side..?

Howdy,

You need to carefully inspect the raw water system.

That will include the hose from the raw water pickup on the bottom to the raw water impeller and on into the oil cooler. impeller failures frequently leave pump fragments in the oil cooler and t-stat.

Also, good flow to one manifold/riser and poor flow to the other is frequently due to the riser or manifold in question being plugged with corrosion.

Some engines also have flow restriction/equalization devices (check balls etc) in the thermostat housing to equalize water flow to each manifold and riser. If one of those "balls" gets stuck (or is blocked with pump fragments/debris etc), you're left with water flowing to one side only.


You can check the flow thru each manifold/riser combination by connecting a water hose to each and observing how well water flows thru it. If you did break the manifold/riser connection be sure to replace the riser gaskets with new ones.




Regards,


Rick

 

[frustratedboater]

Re: Water from one side..?

Thanks greatly for the info. I'll have to take the manifolds off completely and look the whole thing through. I do suspect rust, but where I looked, I didn't see much blockage. I think the manifolds are old enough to be replaced, but that's a costly job!

Are you familar with the water flow route? Does the water flow to the bottom front of the manifold, then to the engine block?

 

[ChrisCraftJohnny]

Re: Water from one side..?

If you have petcocks under the manifolds make sure they are fully open and clear. Sometimes it's the stupid stuff.

Johnny

 

[Bondo]

Re: Water from one side..?

Are you familar with the water flow route? Does the water flow to the bottom front of the manifold, then to the engine block?

Ayuh,....Raw water is delivered to the T-Stat housing where it either goes thru the circulating pump, into the motor,+ heads,...
Or it expelled out the manifolds/ risers...
Hot water is expelled the same way when the t-stat opens...

 

[frustratedboater]

Re: Water from one side..?

Well I guess I'll have to tackle it the hard way and dive right into it. Looks like either way I've got a plugged passage somewhere. That stinks!! Somebody say, welcome to boat ownership...

 

[Howard Sterndrive]

Re: Water from one side..?

Is the boat trailer sideways on a slope?
.... water will flow the path of least resistance...downhill is easier than uphill... if one manifold is lower you will tend to get more going that way... and if the engine is under zero load on a chilly day being fed chilly tap water, the thermostat will be barely opening.


Is the "dry" manifold overheating? hot to the touch? If you can keep your hand on it without pain, it's fine. above 140F you can't keep your hand on it.

 

[frustratedboater]

Re: Water from one side..?

No, the boats pretty level in the driveway. As I put my hand on the manifolds after running a few minutes, the 'closed off' one is much hotter. The right side, where the water flows fine, and is cool to the touch. I probably need a new manifold. Just trying to isolate where the (potential) block is...

I appreciate your asking though..

~FB~

 

[Dshow]

Re: Water from one side..?

If you pull off your exhaust manifold, besides looking for rust in the exhaust passage, is there any way to test whether you have a restriction in the water passage? Besides looking down from the top and trying to see in from the petcock, is there anything else that can be done?

 

[havasuboatman]

Re: Water from one side..?

Something you want to check...
Does it do this only on the trailer?? lower water volume due to a hose adapter can cause this on some marine engines. Especially modified automotive engines.
By right hand side, do you mean starboard side?
If that is the case, you may need a restricter valve on the starboard exhaust manifold water inlet.

 

[frustratedboater]

Re: Water from one side..?

I'm not sure I need to go that route (restricter) given that I had water flow before, and other boats of my model pump it out fine (but not ruling it out), it just wasn't as much as the 'starboard' side of the engine. I'll go through the passage ways and try to track this down. I'm leaning towards a clogged manifold, but hopeful its' not pandoras' box...

~FB~

 

[Howard Sterndrive]

Re: Water from one side..?

I think you're looking for a problem that doesn't exist, but better safe than sorry.
Hope if there is something amiss that it will be obvious when you see it, like something jammed in a riser....