exhaust elbow inspection

[Captain Gadget]

I would like to inspect my exhaust elbow for carbon build up and was wondering if there was an easy way such as removing the output hose or if one must remove the whole unit. The hose looks like it has some sealer on it when it was installed and maybe tough to remove and the mounting bracket probably needs a gasket to be re-installed.
Any comments?

 

[kloudie1]

With a strong light, a mirror and some good eyes you can pull the hose off and look up inside with the mirror and light. You are looking for a carbon build-up that would close the upper part of the exhaust passage. When they really get bad, the hole can be closed by the carbon to 3/4" or less.. It amazed me that the engine ran as well as it did with the hole closed that much.. it did overheat at high power settings..While you are there, pull the little hose at the elbow too and check it to make sure it is completely clear at the fitting.

 

[Claude L.-Auger]

Here are some pics of a cut-off mixing elbow I found a while back on the internet. Don't know who the author is so I can't pay credit but hopefully it will help you visualize if yours needs to be cleaned out or changed.

 

[Jim L]

Now I would like to see a section view of a new mixing elbow. That was an informative visual.

 

[Bob 04 H260]

I just replaced my mixing elbow and manifold this spring, yes there is a gasket at the block.

I noticed it ran much cooler after it was changed. So one indication would be temperature. After mine was changed I could hold my hand on it after 10 minutes of running in the slip, running much cooler than the old one.

Mine seemed to have a heavy mineral buildup rather than carbon, so probably had less cooling going on.

I thought the elbow looked quite sturdy, tried to punch a hole in it with a sharp cold chisel and came to the conclusion it was probably structurally sound. I turned it upside down and filled it with 20% muriatic acid I had left over from a concrete job. I plugged the water inlet with a plastic plug to protect the treads and keep the acid inside. It sat for about 4 days and most of the junk washed out. The inside still had some rusty flakes attached to the walls that I want to clean out. I have been playing with electroplating the rust away using an old battery charger and in a washing soda solution. I made an electrode with a 3/4" steel rod that goes right down into the mixing elbow chamber. I don't like to run it while I am not in the shop so it has only been on about 4 hrs now. It appears to be doing a good job but probably needs about 24 hrs to clean it right up. A bigger power source would shorten the time. From my past experience the electroplating process will only remove the rust and leave the good metal alone. When it is done I'll post some pictures.

I intend to keep this in my spare parts inventory on the boat, it may never be used but I am having fun playing with it and trying to learn something.

good luck, Bob

 

[Bob 04 H260]

One other point, when I bought the new mixing elbow the Yanmar dealer was able to order one that had been removed from a new engine because it was not suitable for the installation of that engine in a new boat. The parts had been returned to the Yanmar distributor by a boat manufacturer. I saved about 35% on the price as I recall.

Bob

 

[spraygun]

If it is cool to the touch on the exhaust side while it's running.. don't worry about it. I check my nearly every time we use the motor. The last time I checked it was a little hot .so I checked the water pump impeller. All is good there. So I took off manifold. Well as everything was rusted together on the threads. So I gotta ball peen hammer and hit the elbow one time and it just shattered into four pieces perfect.... I was thrilled and worried at the same time. Threaded the new one right and job done.

 

[Jim L]

Apparently mine was pretty clogged.

 

[Jim L]

Finally got out this weekend. WOW What a difference in her performance. Really gets up and moves now with power to spare. Tach still only maxes out at 3,000 but at that max rpm I get to 7.5 knots in calm water. still need to figure how to get the throttle from inching back down on its own while motoring.

 

[Allan12210]

still need to figure how to get the throttle from inching back down on its own while motoring.

If you have the Yacht Specialties control head (the part that the throttle and shifter levers are mounted to), there is an adjustment screw to increase friction on the throttle. Take the compass off and look down inside. There is a hole that is right above the shaft for the throttle lever. Inside is a plastic tipped screw. You can tweak it a little with a small screwdriver that will reduce the slippage. Don't turn it too tight or you won't be able to move the lever or worse it will crack the plastic control head.

There may also be a metal clip around the cable down in the engine area that has a bolt on it. Tightening the bolt will put the squeeze on the cable by crushing the sheathing.

 

[Jim L]

I will give it a try. Thanks

 

[Puesta del sol]

Finally got out this weekend. WOW What a difference in her performance. Really gets up and moves now with power to spare. Tach still only maxes out at 3,000 but at that max rpm I get to 7.5 knots in calm water. still need to figure how to get the throttle from inching back down on its own while motoring.

Jim

I used a wire clamp (may not be the technical term). I went to Home Depot and purchased what looks like a u the goes into a straight piece of metal and has two nuts to tighten the u around the cable. I tightened it until the throttle stopped slipping - two seasons and had to tighten just a little this year. I got the idea for my diesel mechanic who said "do this all the time and if u do it you won't have to pay my time and labor"