Water not exiting exhaust, at idle speeds

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lsilver

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I have a 95 sea ray sundancer 330 with 7.4l mercruiser bluewater fwc inboard engines
I am having an issue where the engine gets warm and water is not exiting the exhaust port at side of boat while engine is idle, at higher throttle plenty of water coming out of exhaust, and engine cools down to 160 where it should be.
I replaces raw water impeller, and still same issue, I took end caps off heat exchanger and plenty of water is flowing through.
I checked flow through "t" going to risers and plenty of flow.
I took risers off and inspected them, and they still look ok, walls still thick, and a little rust but not much in water jacket.
I took a garden hose and hooked to risers threaded pipe, and plenty of water going through without restriction.
where else can i look?
 
That water has to going somewhere, that is, if it really is pumping a good amount.

When you did the impeller, did you also change the cam and look at the sealing plate to make sure there were no groves in it?
 
Are you certain that parts of the "historical" impellers are not still lodged up in there somewhere?

The water may be puddling up in there somewhere and will come gurgling out after it builds up enough.
Did you take the hose off the end of the risers to see if it was indeed getting past the risers at Idle?
 
My mechanic Changed impeller and housing. I could not contort that much to do the starboard side
I did not take off hose as in my boat the hose goes into a fiberglass muffler tube, and u have to take off the riser to remove the hose,
I guess my next step is to replace the risers
I am just wondering if there maybe is something past the riser that would impede water out of exhaust, but since engine temp is high till rpm hits around 1000 then I am thinking something is not flowing somewhere

Should I go with ceramic ,stainless or just cast iron
I am currently in fresh water, but may be in salt water next year
 
yes a flapper/ shutter could have fallen down and is blocking a side.

Tell your mechanic to look for it.
 
I have fwc 454 crusaders and i dont have that much exiting my exhaust either but the water is warm not hot so im sure it flowing fine. I dont think your set up has flappers and you most likely have a 4inch tube so maybe something nested in your exhaust over the winter.
 
Below is a picture of risers.
the walls seem pretty thick to me

I don't think there is a nest or flapper as when I move throttle to 1000rpm + the water flows nice,and temp is goo but when idle the temp goes hi to around 190 ish and would that happen with a blockage?

risers.jpg
 
I think the risers look fine. I you can swap the pumps easily see if that changes anything, sometimes the pump looks good but has worn out.
 
+ 1 I'll go with your pump may just be worn out. Look for any water coming the front of it at idle, also the thur-hull could be clogged up.
 
I had the pump replaced so I know it is good. will try and poke through the through hull and check the heat exchanger again
 
hopefully the replaced pump is new not a rebuild. if there is good flow at the T for BOTH risers then everything before it should be fine.
and there isnt much beyond it to restrict the discharge, riser, exh tube to muffler then discharge port overboard. a clogged oil cooler can
raise the temp but thats usually right after the pump so the flow beyond that would be weak. when you say warm, how warm?
its nice to have a temp gun handy to verify actual temps vs temp gauge. do you have full fwc or a half system?
 
temp goes to around 190 according to temp gauge, as soon as i run some throttle, it goes straight down to 160 where the other engine is
I don't have a gun, as far as fwc not sure what a half one is, everything is running on antifreeze but the risers if that is what you mean
 
Do you have sea strainers? If so, make sure the cap is tight and the cork gasket is sealed correctly. It could be allowing air into the system and decreasing the water flow.
 
i went and reinstalled the risers, still not enough flow,i pulled the end caps off heat exchanger found a few things in strainer, but not alot, pulled off hose feeding exchanger and put my hand on it enough pressure to force hand off, then replaced hose and endcaps and tried putting my hand on hose leading to riser, there is water flow, but not a huge amount of pressure
 
Just my thoughts here. The engine is running warmer than it should be while at idle with a reduced exhaust flow.
It cools down as the rpms are bumped up. I would be looking more at the intake side than the exhaust side.
Reason being that if there was blockage on the exhaust side I would think the temperatures would increase as the blockage would become
more of an issue. If there was an air leakage on the intake side, raising the rpms would then proportionaly allow more water into
the coolong system versus air.
 
Agree the intake should be the problem. You can change the impellers but if the wear plate is slightly worn it will produce the same results you see. I'd change the entire assembly before anything else.
 
entire assenbly was changed, it was impeller + plasticv housing and all hardware
 
Are you saying the pump was the problem??

You got VERY good advice.

Only thing I can add is check water exit passages in riser and thermostat balls
for free movement. Spring can get weak, too.
 
no I am saying all hardware in pump was changed and still have issue
 
Have you checked the transmission cooler?
 
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