Hot water issue

[km1125]

Wow, that's interesting. I would think if your engine circulation pump was weak or faulty you'd have overheating problems. Do you have an IR temp gun to check various areas on the block? If you see huge differences then I'd agree that the circulation pump could be a problem but if the majority of the block and heads are +/- 10 degrees then I'd say that the circulation pump is working.

Interesting on those two exhaust hoses. Those temps should definitely be tied to the raw water pump. I'm not sure on the Mercs, but do those two smaller hoses on the top of the thermostat housing go the the risers (which then dump into the exhaust)??

Just curious.. do you know what temp thermostat is in there?

[Jean-Pierre]

Just ordered a IR gun from amazon 1/2 hour ago !
Decided to change the pump or maybe just the impeller.....( 200 CAD $ my marina says ) Friday morning I'll start working on it. I don't know If the pump was ever replaced, got the boat last Fall.
The 2 little hoses go to the Elbows, and that is cold water, and there are 2 others hoses from the top of the T-stat going to the manifolds. ( hot water )

[bud37]

If the risers are the same relatively cool temp. There is a diffuser where the hoses connect to the riser that distributes water in a pattern to cool the hoses....if the hose is at the wrong angle it will disrupt the cooling flow and just shoot down the hose without cooling the circumference of the hose evenly.
The IR gun will show lots....

Edit ....also I am not convinced your plumbing is to the right places judging by the picture there.....hard to see exactly where they go and come from.
Feed should be from the intake manifold before the thermostat and return should be to the water pump housing.That is the only way to have good flow if you have raw water cooled engines. If you can see a manual for your engines it will show the appropriate places/fittings to connect to.

[Viper]

Pull the hoses at the t-stat housing going to the exhaust elbows and ensure the little ball on each side moves freely. A stuck ball will restrict flow to the elbow. They are supposed to open up at higher rpm/pressure. You may also want to remove the exhaust hoses at the elbows and check the water discharge passages. These passages are narrow and have a tendency to rust and will restrict flow, especially in brackish and salt water. When you get your IR gun, check the temps at the hoses leaving the elbows, those hoses can't take as much high temps as one would think.

When the pump is off, check the inside of the housing. If it's scored, get the rebuild kit that includes a new housing, wear plate, seal, and impeller.

[Jean-Pierre]

Source of the post If the risers are the same relatively cool temp. There is a diffuser where the hoses connect to the riser that distributes water in a pattern to cool the hoses....if the hose is at the wrong angle it will disrupt the cooling flow and just shoot down the hose without cooling the circumference of the hose evenly.
The IR gun will show lots....

Edit ....also I am not convinced your plumbing is to the right places judging by the picture there.....hard to see exactly where they go and come from.
Feed should be from the intake manifold before the thermostat and return should be to the water pump housing.That is the only way to have good flow if you have raw water cooled engines. If you can see a manual for your engines it will show the appropriate places/fittings to connect to.

The heater plumbing is as you said. From the engine block ( between the rocker cover and Carb. ) going through the water tank and back at the big "T" fitting at the suction side of the circulating pump.
But for now I've abandoned the water heater issue....

Went for a ride yesterday, let my girlfriend drive and I went into the engine room....smoke coming from that lava hot rubber exhaust pipe.

So today, all day long... removed raw water pump, engine circulating pump, most hoses , no blockage nowhere. pumps are good. no missing rubber impeller parts. Could not remove the hose from the oil cooler, but did use a garden hose to flush every hoses I had disconnected, nothing wrong. Remove that big burning rubber exhaust hose ( that was hard !!) at the exit of the elbow, used the garden hose, good flow all around the perimeter, did the same with the exhaust manifold water hose, same result, started the engine with both elbows water hoses disconnect ( Left, right ), at the T-Stat housing, water came out both side equally around the not so round plastic balls.
Started the engine again with all hoses re-connected but with big rubber exhaust pipe disconnected, Big splash of black water out all over the white carpet.........

Re-connected everything as original, started the engine, rubber exhaust still burning and smoking. Here is a picture with the temp. taken with my IR gun while under way. With my hand I can feel that the bottom is way cooler than the top of the rubber pipe. meaning bad water flow around the perimeter..... The garden hose has more pressure & flow.........

The exhaust manifold (metal) ( the side with the burning rubber , I did not measure the other one. ) was at 190 F . Oil filter temp. = 180 F Water temps gauge = 150 F, 1100 RPM both engines.

The measurements were taken with only one floor panel removed, not like the picture, so I did not have access to the right side of that engine, but took measurement of the port engine, right exhaust, ALL the measurements were the same except for that 350 F, which was 120 F on the other engine.....

When I re-installed the exhaust rubber pipe, I lifted it as much as I could, to align it with the elbow exit angle....

[bud37]

https://www.google.com/url?sa=t&rct=j&q ... 5hgAGqYHrs

Here is a link for a video to give you a good visual of how that section works. I am not saying that this is the problem and the fix but will be a good visual to see how the water flows.Hopefully this resembles what you have.

One thing for sure, regardless of what you find, that hose section that has been overheated/burning needs to be replaced as it is no longer any good.....the rest of that side will have to be inspected for damage also. FYI....there are several choices for replacement hose, some are thicker and have a higher temp rating etc, just be aware when purchasing your replacement.

[Jean-Pierre]

I've replaced the raw water pump with a brand new one, even thought the old one was in perfect order.
Same problem with the hot rubber.
Replace the thermostat just in case, but same problem, at least i'm getting to know my engine....
Removed the elbow, 2 small round holes were clogged in the gasket, so I installed a new gasket, flushed the elbow with garden hose, no blockage, and nice waterfall out from the top . reinstalled but still same hot spot on the new rubber 4" hose. In the picture, at the bottom of the elbow, there is a small hole, I don't know if its normal ?

Removed the hose where the check balls are, ( T-Stat housing ) turned them around because they were not round on the matting side, same results, hot rubber !

JP

[Jean-Pierre]

today I installed a clear pvc hose on the fitting with one of the plastic ball, going to the elbow, started the engine, I could see a nice water flow and the ball happily springing.....

Took the whole T-stat housing from the good engine , same results, the rubber exhaust is very hot at several spots where the water should be mixing with the gas.

I started both engines and went outside to look at the exhausts, notice that the good engine had water flow like prop was turning ( but I was in neutral of course ) and the other ( bad exhaust ) no movement in the water.....

jp

[bud37]

Do you see the same small rusty hole on the other good side.....you definitely have water flow issues. I can't help with it any further, but if it were me I would check and compare to the good side to see if the same type of hole exists, then you will know what is up hopefully. Something may be short circuiting the flow out the mixer at the top where the hose fits causing the exhaust to fry the rubber. Nice job picking thru it so far.. Good luck man I think you have got this...

Maybe someone has some experience with this particular elbow riser and can chime in.

[bud37]

I have since looked at some pics of sierra parts and it appears there is that second hole at the bottom on them like you are showing..not sure what that means for you....what is the name on your stuff, is it original merc ?