I have a Yanmar 3GM30F on a Hunter 35.5. The PO cut an opening in the rear so access is good. My problem is I can get all the hoses off and get the bottom portion loose but I can not budge the top thread. The elbow is attached to the manifold with a double threaded sleeve, and the top is frozen. I assume the threads both are standard? Any ideas on how to loosen it?
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Replacing Exhaust Elbow
Just finished the same job. Don't even try to separate these two castings in place. The manifold is attached to the back of the heat exchanger with four horizontal bolts which are all easy to remove. Unless you have access to lots of muscle and a heavy duty vice, you should then take the two joined components to a Yanmar shop and ask them to install a new mixing elbow. My shop sold aftermarket mixing elbows for a much lower price than genuine Yanmar. They may have to apply heat to the threads to help the castings come part. Note that the two threads are opposite hand to each other. Also mark the vertical orientation of the two castings and make sure that the rebuilt assembly matches this or it will not fit into the available space. I also found it impossible to reinstall the main hose in place. Do this on the bench and then install this hose and both castings as one unit on the boat. Good luck.
Just finished the same job. Don't even try to separate these two castings in place. The manifold is attached to the back of the heat exchanger with four horizontal bolts which are all easy to remove. Unless you have access to lots of muscle and a heavy duty vice, you should then take the two joined components to a Yanmar shop and ask them to install a new mixing elbow. My shop sold aftermarket mixing elbows for a much lower price than genuine Yanmar. They may have to apply heat to the threads to help the castings come part. Note that the two threads are opposite hand to each other. Also mark the vertical orientation of the two castings and make sure that the rebuilt assembly matches this or it will not fit into the available space. I also found it impossible to reinstall the main hose in place. Do this on the bench and then install this hose and both castings as one unit on the boat. Good luck.
tip!
Take a look at this. It will not supply all the answers but it is a start. The easiest way to work on the elbow is to remove the manifold & elbow from the engine. Do the work on a work bench and then reinstall. It is sometimes easier to just replace the entire unit (manifold, coupling & elbow). Be sure to check out the exhaust hose too.
Take a look at this. It will not supply all the answers but it is a start. The easiest way to work on the elbow is to remove the manifold & elbow from the engine. Do the work on a work bench and then reinstall. It is sometimes easier to just replace the entire unit (manifold, coupling & elbow). Be sure to check out the exhaust hose too.
A heat gun may help too
I also just had to replace the elbow a few weeks ago. My shop told me that the elbow and manifold piece are reverse threaded together, which made it virtually impossible for me to work on (that and 16 years of carbon build up in the elbow...) Reinstalling the whole piece to the engine wasn't too bad, the hard part for me was working with the exhaust hose. I had to remove my hose from the muffler to get the elbow out. I hope I NEVER have to work on the hosing again, but I used a heat gun (along with some extra muscle) to make it somewhat pliable when reinstalling the elbow.
I also just had to replace the elbow a few weeks ago. My shop told me that the elbow and manifold piece are reverse threaded together, which made it virtually impossible for me to work on (that and 16 years of carbon build up in the elbow...) Reinstalling the whole piece to the engine wasn't too bad, the hard part for me was working with the exhaust hose. I had to remove my hose from the muffler to get the elbow out. I hope I NEVER have to work on the hosing again, but I used a heat gun (along with some extra muscle) to make it somewhat pliable when reinstalling the elbow.
Left Hand Thread
Probably repeating what was stated in Steve's link, the coupling has a left hand thread on at least one side. As the previous posters have advised, take the whole assembly off first, then separate on the bench. I wrapped my coupling with teflon tape when I put it back together just to make it easier next time. Don't forget to install a new exhaust gasket.
Probably repeating what was stated in Steve's link, the coupling has a left hand thread on at least one side. As the previous posters have advised, take the whole assembly off first, then separate on the bench. I wrapped my coupling with teflon tape when I put it back together just to make it easier next time. Don't forget to install a new exhaust gasket.
I think I got it
Thanks for all your replies, and to Steve for documenting the procedure with pictures. I will try the manifold tonight.
Thanks for all your replies, and to Steve for documenting the procedure with pictures. I will try the manifold tonight.
I remove the exhaust manifold...
put the entire assembly in a large bench vise, soak it with penetrating oil and the use a big wrench and a breaker bar. Sometimes this works and sometimes it doesn't and I end up using a hack saw and a cold chisel. I always have to replace the double threaded sleve. Good luck.
put the entire assembly in a large bench vise, soak it with penetrating oil and the use a big wrench and a breaker bar. Sometimes this works and sometimes it doesn't and I end up using a hack saw and a cold chisel. I always have to replace the double threaded sleve. Good luck.
Sealant
What type of sealant is recommended for the threads of the joints of the elbow,manifold and coupler piece. In order to line up my water hose connection my joints cannot be wrenched tight and has a slight exhaust leak. I assume teflon tape won't work because of the heat????? Thanks as always.
What type of sealant is recommended for the threads of the joints of the elbow,manifold and coupler piece. In order to line up my water hose connection my joints cannot be wrenched tight and has a slight exhaust leak. I assume teflon tape won't work because of the heat????? Thanks as always.
Don'y use sealent like taflon tape
use anti-seize on all of the threads, and don't tighten it too tight. The heat will expand it and make it a good snug fit. If you tighten it too much, well, you will have a real tough time getting them apart next time.
use anti-seize on all of the threads, and don't tighten it too tight. The heat will expand it and make it a good snug fit. If you tighten it too much, well, you will have a real tough time getting them apart next time.
Cut out for exhaust Elbow
In response to question from Honeyman, I will try and post a picture but that may take a few days. The PO left a gaping hole where he cut out he wood and the insulation - my guess is it is about 16" X 16". I had a cover made of some good quality canvas which is 3-4" wider all around than the cutout. I then had velco strips sewn into the edge and applied velcro tape around the out side of the cutout. I also got a piece of the engine insulation which fits over the entire cut out and is held snugly in place by the velcro.
In response to question from Honeyman, I will try and post a picture but that may take a few days. The PO left a gaping hole where he cut out he wood and the insulation - my guess is it is about 16" X 16". I had a cover made of some good quality canvas which is 3-4" wider all around than the cutout. I then had velco strips sewn into the edge and applied velcro tape around the out side of the cutout. I also got a piece of the engine insulation which fits over the entire cut out and is held snugly in place by the velcro.
Yanmar Rear Bunk Access Hatch
Honeyman asked for a picture of the rear engine access hatch that a previous owner had made. I don't have a picture but can very easily describe how I made mine. Run masking tape down the the approximate line of the proposed rectangular opening on the front bulkhead of the rear berth - which on my boat is teak ply finished. Check on the inside of the engine compartment that cutting along this line will not damage a hose or cable. Pencil straight lines on this tape to use as a cutting guide. Drill holes at the corners to start a sabre saw. Cut out the rectagular hatch with the sabre saw. Select some 2" x 1/2" rectangular hard wood moulding and stain it to match the teak. Frame the cutout piece with the moulding using mitred corners, overlapping the edge by about 1". Glue the moulding frame on the cutout piece. Reinstall the cutout piece on the boat using 2-3 small SS screws through the protruding part of the moulding to hold it in place. A very easy job that really opens up the rear of the engine. Did something similar on the top of the engine compartment too. What a difference. How else does anyone work on these engines?
Honeyman asked for a picture of the rear engine access hatch that a previous owner had made. I don't have a picture but can very easily describe how I made mine. Run masking tape down the the approximate line of the proposed rectangular opening on the front bulkhead of the rear berth - which on my boat is teak ply finished. Check on the inside of the engine compartment that cutting along this line will not damage a hose or cable. Pencil straight lines on this tape to use as a cutting guide. Drill holes at the corners to start a sabre saw. Cut out the rectagular hatch with the sabre saw. Select some 2" x 1/2" rectangular hard wood moulding and stain it to match the teak. Frame the cutout piece with the moulding using mitred corners, overlapping the edge by about 1". Glue the moulding frame on the cutout piece. Reinstall the cutout piece on the boat using 2-3 small SS screws through the protruding part of the moulding to hold it in place. A very easy job that really opens up the rear of the engine. Did something similar on the top of the engine compartment too. What a difference. How else does anyone work on these engines?
Cut out no necessary
I changed the Elbow this spring and a cut out in the aft stateroom for the 35.5 is not absolutely necessary. However I found that the bet technique for disassembly is to remove all components at once, a four bolts affair, including manifold, coupler and elbow. Bring everything to the workbench, use a torch to heat the coupler, undo the 3 components, scrape the old gasket from the manifold and motor, install a new one and find a way to make it stick there during installation, re-assemble the manifold / new gasket assembly to the coupler and new elbow. I did not use any sealant. Make sure parts orientation is perfect because space will be tight during re-installation. Fix the assembly to the motor and then put the muffler hose back in place. This is the most difficult job because the hose is rigid and the elbow is at an angle. The top of the hose should be cut with a slight angle too for the best fit. The entire job took me 2 hours and I am not a mechanic. Good luck
I changed the Elbow this spring and a cut out in the aft stateroom for the 35.5 is not absolutely necessary. However I found that the bet technique for disassembly is to remove all components at once, a four bolts affair, including manifold, coupler and elbow. Bring everything to the workbench, use a torch to heat the coupler, undo the 3 components, scrape the old gasket from the manifold and motor, install a new one and find a way to make it stick there during installation, re-assemble the manifold / new gasket assembly to the coupler and new elbow. I did not use any sealant. Make sure parts orientation is perfect because space will be tight during re-installation. Fix the assembly to the motor and then put the muffler hose back in place. This is the most difficult job because the hose is rigid and the elbow is at an angle. The top of the hose should be cut with a slight angle too for the best fit. The entire job took me 2 hours and I am not a mechanic. Good luck
Excellent description...
Neil, very well written. Staining any moulding to match the teak is a real challenge that I haven't mastered yet. Claude, I'm glad to hear you were able to complete the repair without better access. I'd really like more room to get at things, but would at least start without. It's always interesting to see how people have modified their boats for better access.
Neil, very well written. Staining any moulding to match the teak is a real challenge that I haven't mastered yet. Claude, I'm glad to hear you were able to complete the repair without better access. I'd really like more room to get at things, but would at least start without. It's always interesting to see how people have modified their boats for better access.
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