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View Full Version : Hot Exhaust water ???? 2001 ZX twin 350s



stationinc
01-08-2012, 01:37 PM
Have a 29ft 2001 Donzi ZX with twin 350s
The exhaust on 3 of the 4 banks ( cool to warm water )
One bank is hot to very hot

Does anyone have any ideas what would be my issue

Thanks
Q Jones
Reply to: >>>> stationinc@aol.com

Morgan's Cloud
01-08-2012, 01:56 PM
I had a friend with the same boat and engines and probaly the same year ..can't remember exactly .. When he had one ongine that started to run hotter than the other it almost bankrupted his boating budget before it was finally diagnosed as the grommet on the transom plate where the external water transfer hose connects to the internal water hose. Water flow/overheating problems can be a beyotch to nail because there's so many things that can cause them.
If you do a search under 'overheating' you'll have enough reading material to keep you up for days .. and that's only on this one site !

Have you done any trouble shooting yet , changed impellors , inspected risers etc ?
Are you in salt water too ? The standard cast iron exhaust systems really only have a 'safe life' of about 3-4 years in salt ... if that .

stationinc
01-08-2012, 04:24 PM
I will check it out, the big question I have is why one bank is hotter than the other on the same engine
You can place your hand on one bank, warm & the opposite bank is very hot

Thanks for any imput
Q Jones
stationinc@aol.com

Morgan's Cloud
01-08-2012, 05:02 PM
The way the GM V8 block splits it's waterflow is a little odd from what I've learned. You can be fine and good to go in all aspects but if you run it on a hose in the yard you can get one side (Manifolds) that show an overheat problem with little water coming out of the port exhaust dump , even though everything is ok.
Is this what you're experiencing or do you have one engine that is actually 'hot' and the other has a 'split difference' ?

stationinc
01-08-2012, 05:25 PM
The heating issue is both, running the boat in river & on flushout
I flush these engines after every use, because we mainly run in salt water

The one engine in question is the older of the two engines
The newer one runs great w/ both banks running warm as expected

The older engine seems to run fine but one exhaust side is hotter that the other

Keep-em coming
Thanks
Q Jones

Ghost
01-08-2012, 06:33 PM
How many seasons on the manifolds and risers?

Morgan's Cloud
01-08-2012, 06:45 PM
Do you haul you boat after every run ?
I'm not an expert on this topic but I have seen a few strange things on this subject in the past.
From what we learned with my friend's 28ZXO/350 Mags the problem is actually magnified with boats that are run in the briney and hauled , despite even being flushed immediately after use. The engines are flushed with fresh water but the salt remains around the transfer passage on the transom housing and then the transfer bushing starts to crush from corosion. In terms of when you might be eligible for this probem ,you are there NOW .

Meanwhile , everyone else around here is probably laughing as I try to offer a bit of help before they chime in .. :tongue:

stationinc
01-08-2012, 10:18 PM
I am the 2nd Owner
1st owner was in the Atlanta area (fresh water)

This will be the 2nd full season for me in (salt water)

Yes, I haul the boat in after every use
I am going to check these different suggestions out as soon as the temp outside gets up

Thanks for all of them
Any other suggestions ??????

Thanks
Q Jones

younger
01-09-2012, 12:29 PM
Check thermostat and housing, all hoses and manifolds for blockage and routing of the hoses. Is the hot motor exhausting the same amount of water as the cool engine if not check water cooling pump and impeller. Compare the hose routing with the cool motor that nothing is kinked or funky. If the pump is suppling good flow of water, the motor fills and divides at the therm housing to the exhaust if open cooling. The flow out each exhaust bank should be equal. Pull the spark plugs on the hot side to confirm that you have no water getting in that side of the motor from a detereating manifold. If there is any blockage in cooling system the water will take the easy ride out. Best of luck.

biggiefl
01-09-2012, 02:05 PM
You should check your riser gaskets every season if in salt. I would start there.

MOP
01-10-2012, 09:13 PM
My guess would be risers, simple test. Run it on the hose a 1K RPM hold a bucket for 30 seconds catching the water from the cooler outlets one at a time, mark the buck then hold it under the hot side. My guess it will be quite a bit lower in volume.

Phil

FISHIN SUCKS
01-11-2012, 06:47 AM
I had the same problem you are having. replace the manifold and riser. You have rust in there that is plugging it up. that was my situation anyway.

CHACHI
01-11-2012, 06:57 AM
I too had the same issue, one bank running hotter than the other.

After all the riser cleaning I could stand, with no debris found, I finally backed up and went to the water pump.

Although the impeller was new, (4 hours) the plastic housing was worn and the pump just wasn't pumping enough water.

Changed the back half of the pump and now the manifolds are with in 4 degrees of each other.

Oh, I also only boat in fresh water.

Ken

Ghost
01-11-2012, 09:11 AM
Still wondering how many seasons are on the manifolds & risers (not how many seasons you've owned them, but how many seasons they have been in use). If they are original (2001), I would change them immediately, regardless of whether anything else is wrong. Good chance they are the problem anyway, as others have noted.

zelatore
01-11-2012, 01:50 PM
MOP
My guess would be risers, simple test. Run it on the hose a 1K RPM hold a bucket for 30 seconds catching the water from the cooler outlets one at a time, mark the buck then hold it under the hot side. My guess it will be quite a bit lower in volume.



Ghost
Still wondering how many seasons are on the manifolds & risers (not how many seasons you've owned them, but how many seasons they have been in use). If they are original (2001), I would change them immediately, regardless of whether anything else is wrong. Good chance they are the problem anyway, as others have noted.


^^^this

johnny50
01-13-2012, 06:08 PM
I had the same problem with the 99 454 mpi motor I have in my '93. I took the hoses off from the transom and checked the cool fuel module, oil cooler and p/s cooler. I fould small water pump impellor parts (before the water pump???) and gravel plugging the holes in the cooler. I had a hose on to flush them and the flow looked great. The gravel was lodged so tightly in the small cooler holes that the cooler needed replacement. It now runs perfect.
How much water flow is entering the manifold on the hot side?

joseph m. hahnl
01-13-2012, 07:13 PM
Water pump Impeller is a good place to start, as it is never a wast of time or money to put a new one in. Also note that as being second owner there is no telling if the previous owner neglected the water pump and lost a couple of impeller fingers.

But first things first:yes:

Run it on the hose a 1K RPM hold a bucket for 30 seconds catching the water from the cooler outlets one at a time, mark the buck then hold it under the hot side. My guess it will be quite a bit lower in volume