Hot water issue

[km1125]

I'm wondering if this is one of those engines that have a "flapper" valve in the exhaust somewhere. I've never had one, but I understand if that flapper breaks off it could jamb in the exhaust. I'm wondering if exhaust backpressure might be blocking the flow of cooling water and forcing more of it to the other side.

What do you other guys think that may be more familiar with this model of motor?

[Jean-Pierre]

Today I will removed both elbows to compare. and swap sides.
Its all original mercruiser parts, I will check inside the piping to see if there is a blockage but these rubber hoses are hard to remove.
The water movement I saw is the prop turning in neutral.....I went under the bed and saw the shaft turning, I could stop it with my hand, another adjustment to make....

JP

[Jean-Pierre]

Verified with another elbow, the bottom hole is normal.
Removed all piping ( exhaust ) between elbow and muffler, no dead animal.

JP

[bud37]

A couple questions......does it look like the system you are having trouble with was recently apart if this is a new boat to you.
Have you checked where the water goes into the manifolds from the therm housing.... look inside for impeller bits.
Is this a fresh water boat.

It really is a puzzle as to where the restriction is, I am surprised there has not been more chimes on this.

[Viper]

Can you post the engine serial number?

[Jean-Pierre]

Ok this morning I decided to check the oil cooler and guess what I found, yeah yeah I should have check that before.....
So , parts of old rubber impeller and other FOD that I have not completely removed yet, these rubber parts must have been there for years ! because last week I did replace the raw water pump and the old one was in perfect shape.

Friday I will continue cleaning the cooler and test afterwards.


JP

[Jean-Pierre]

engine serial is 0D700214

2 weeks ago everything was find, but I started playing around with the first problem which was the hot water tank issue, maybe I dislodge the FOD while manipulating the hoses and it came to rest at the cooler.... ?
JP

[Viper]

Do you have risers between the manifold and elbow?

[Jean-Pierre]

Source of the post Do you have risers between the manifold and elbow?

No risers, the elbows are directly bolted to the manifolds, which I completely removed today, heavy piece ! Flushed both manifold and elbow with garden hose, no leak between gas path and water jacket. reinstalled with new gasket.

Collected additional rubber parts from impeller, in the oil cooler inlet and hull floor, so much that I decided to verify the pump I installed last week....all good

ran engine 10-15 minutes, exhaust hose smoking. started without the T-Stat, same thing....

Tomorrow I will swap through hull water inlet just in case the STBD is clogged, which I doubt because when the hose is disconnected at the ball valve, water is coming good, enough ? I don't know.

Found round mesh screen under the oil cooler,on the hull floor, probably came out when I removed the hose, to hard to put back for now.

[Jean-Pierre]

I swapped the 2 elbows yesterday, and the problem did not follow....so it's not the elbow, I removed once again the manifold and reflush with a garden hose, but more aggressive, and got approx. 1 cup of rust corn flake. I was almost happy, reinstalled everything but still burning the rubber hose....
Removed again...brought the elbow and manifold home to investigate, can't find anything wrong with these parts. Flushed and nothing is blocked, borescope, good water flow but Ordered a new manifold anyway, but I'm pretty certain it wont fix my problem....but....

JP