5.0 Litre EFI TBI 2000 water blockage5.0 litre 2000 Mercruiser cooling question

[iisinc]

I am working on a 2000 5.0 litre Mercruiser I/O with a brovo drive. a number of years ago, I had a problem with this boat overheating and found the water inlet from the IO was collaped, I repaired it and all was well for a few years. Most recently, this engine has had all new manifolds and risers + valve job. I diagnosed low water flow again, so, I put in a direct thruhull water inlet, blocked off the transom inlet and the manifolds run nice and cool now. However, now when I bump up the rpm's to plane the hose that goes from the thermostat housing to the circulation pump expands and looks like it's about to blow! I have changed the thermostat and the housing is clear. Manifolds are running nice and cool and a check with an infared thermometer is shiowing about 160-170 degrees. BTW, the circulating pump is new and the main feed hose to that pump is also new. Does this sound like a blocked engine blockage?? Any ideas would be helpful.

 

[Don S]

Re: 5.0 Litre EFI TBI 2000 water blockage5.0 litre 2000 Mercruiser cooling question

Moving this over to the Mercruiser forum for you.

Pull the thermostat housing and check inside, their should be a bypass hole in the cast passages that is probably plugged up. Clean it out and I bet it works better.

 

[cr2k]

Re: 5.0 Litre EFI TBI 2000 water blockage5.0 litre 2000 Mercruiser cooling question

Also feel around in there is some there is a hole that you can't see due to where it is but will do the same thing.

 

[iisinc]

Re: 5.0 Litre EFI TBI 2000 water blockage5.0 litre 2000 Mercruiser cooling question

Thanks, I have the thermostat housing off and seems like all is clear. My next step is to backflush the block to see if there is anything blocking the flow in the engine, although, I have never before seen this problem.

 

[iisinc]

Re: 5.0 Litre EFI TBI 2000 water blockage5.0 litre 2000 Mercruiser cooling question

I will let you know what happens next.

Thanks again.

 

[iisinc]

Re: 5.0 Litre EFI TBI 2000 water blockage5.0 litre 2000 Mercruiser cooling question

To those trying to help, I found another thread in here, that indicates exactly the same symptoms. In his case, it ended up being old flappers stuck in the exhaust near the outdrive. We are going to remove the outdrive tomorrow,so, I will let you know what I find.

 

[Don S]

Re: 5.0 Litre EFI TBI 2000 water blockage5.0 litre 2000 Mercruiser cooling question

Broken flappers couldn't do that in a million years. If it did back up water so the hose got hard, the engine wouldn't run because of the water in the exhaust.
I've seen lots of replies of what someone found was the problem and it actually wasn't. Was more of an excuse to cover up what really happened.

 

[iisinc]

Re: 5.0 Litre EFI TBI 2000 water blockage5.0 litre 2000 Mercruiser cooling question

Don,

Thanks for the feedback; I'm positive I will find the source of this problem with your, well appreciated, help.

 

[iisinc]

Re: 5.0 Litre EFI TBI 2000 water blockage5.0 litre 2000 Mercruiser cooling question

Update:
This morning, I again looked very closely at the thermostat housing, and, sure enough way inside was a piece of impeller rubber stuck in the bypass portion of the part. It is not easy getting something out of there. I have not yet reassembled it on the motor to test, but, I have every confidence that the blockage was the cause of the circulation hose swelling. Thanks very much for your help and timely feedback.

 

[TilliamWe]

Re: 5.0 Litre EFI TBI 2000 water blockage5.0 litre 2000 Mercruiser cooling question

Those impeller blades can get stuck in the darndest places, for sure.