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GM 454 Leak

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trido

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« on: October 13, 2015, 12:42:20 PM »
Hey guys,
New to the forum! I have a leak coming from the motor and can't seem to find where its coming from.

Here's the scenario:
When the engine is cold everything is fine, after setting on the throttle for about 5 to 10 minutes water starts spraying from under the engine somewhere. When I let off the throttle it still sprays  while idling. When I turn off the engine it stops. After I let it sit for about 3 to 4 mins or so, I turn the engine back on and the leak is gone until I'm on it again for about 5 to 10 mins and the whole process starts all over. The problem is, the leak only happens when I've been at full throttle for a while so I'm not even sure I can replicate the problem on the trailer with a garden hose.

Any suggestions? I have a trip to Avi planned this Saturday and want to get it diagnosed and fixed before then.

 If I can't figure it out in the next couple days I may need a mechanic, if thats the case any recommendations in the Orange County area?
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GT Jets

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« Reply #1 on: October 13, 2015, 01:15:31 PM »
Is there water in the bilge at the time?  Could it just be spraying out of the bell housing being flung by the flywheel?

Maybe when you shoot it off either the bilge pump clears it out our the water migrates forward?

I'm also curious about the shaft seal condition.

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trido

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« Reply #2 on: October 13, 2015, 02:10:31 PM »

Is there water in the bilge at the time?  Could it just be spraying out of the bell housing being flung by the flywheel?

Maybe when you shoot it off either the bilge pump clears it out our the water migrates forward?

I'm also curious about the shaft seal condition.

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As far as the bilge goes it pretty dry until the water starts spraying out. The water seems to be coming somewhere midway from just under the motor not at the ends of that makes sense. I contacted the guy I bought the boat from and he seems to think it just a leaky hose somewhere that only leaks after it builds up pressure. Is this even possible on an open ended cooling system?


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Riverrat817

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« Reply #3 on: October 13, 2015, 06:44:31 PM »

As far as the bilge goes it pretty dry until the water starts spraying out. The water seems to be coming somewhere midway from just under the motor not at the ends of that makes sense. I contacted the guy I bought the boat from and he seems to think it just a leaky hose somewhere that only leaks after it builds up pressure. Is this even possible on an open ended cooling system?

Just thinking out loud here. Are you using headers with a tee-valve? You might have a leak in one of the hoses after the tee-valve. Could explain why you don't have a leak at idle since the tee-valve doesn't open until 1800+rpm. There is a lot of smart members on this site that will probably have a better answer than me but figured I'd throw it out there.


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crewchief22

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« Reply #4 on: October 13, 2015, 07:32:22 PM »
Just thinking out loud here. Are you using headers with a tee-valve? You might have a leak in one of the hoses after the tee-valve. Could explain why you don't have a leak at idle since the tee-valve doesn't open until 1800+rpm. There is a lot of smart members on this site that will probably have a better answer than me but figured I'd throw it out there.

The pic in his profile doesn't look to have headers.

I'd suggest looking at the gaskets between the logs and risers for signs of leaks.  It might not be pressure as much at heat causing the issue.

Good luck and welcome to SCJB  ;D
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« Reply #5 on: October 14, 2015, 06:08:13 AM »
I would still hook up the garden hose and put my finger over the exit to create some pressure.

If there's a weak link somewhere this might help it to show itself.

Simple test to try and you can't hurt anything.

69kona

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« Reply #6 on: October 14, 2015, 06:56:28 AM »
If it were a hose like the PV owner said it would be leaking all the time running . I bet the flywheel is fling up the water 
Good luck


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trido

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« Reply #7 on: October 14, 2015, 04:21:23 PM »
So today I had a chance to run the boat on the trailer. Ran it on and off for about 30 mins letting it idle, then brining up the RPMs and still no leaks from anywhere. I can't see anywhere on the engine or exhaust manifolds with even a drop of water.

Starting to think the leak is coming from the hull itself or maybe the pump and as some of you already mentioned the fly wheel is splashing the water around. After it sits it probably stops as the bilge pumps pump out the water. Then I'm assuming it's filling up again as I'm driving around. Is there a seal in the pump that might be causing this?

Thoughts?

Thanks for all the help on this guys! I've included a pic of the engine as some of you were asking about the exhaust manifolds.


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