exhaust repair Yanmar YSE 12

[J Hunter]

I have a '76 Hunter 30 with the subject motor repair required, I ordered the parts from Torrensen and expect them this week. I did this repair once before in about '86, the parts have changed a bit so I thought I'd ask the group for input.

To see if you have worked with this setup or something close here's what I'm looking at. The exhaust leaving the motor block has 3 pieces before it ends at the hose going to the stern:

1. a 90 degree elbow bolted to the block and looking toward the overhead with female pipe threads. 2. A metric right hand/ left hand pipe nipple screwed into the elbow approx 1.5" I.D X 10" looking upward. 3. A 180 degree mixing elbow with the nipple coming from the engine screwed into the inlet side, a cooling water inlet fitting looking abeam out one side and the stern hose hitched to the outlet end which looks toward the bilge.

The defect is the bottom end of the nipple (2) I found just loosely sitting in the female threads of the exhaust elbow. I didn't do a real close well lit inspection of it, but it didn't look like there was a broken or rusted off piece of the nipple left stuck in the exhaust elbow. I decided to get all three parts on order in case I need them all, when I did in talking to Torrensen, I found out that Yanmar now supplies a much shorter right hand/left hand nipple (3 1/2") instead of the approx. 10 " long one that's in there now. Does anyone think I should be concerned with the 7" drop in the elevation of the mixing elbow relative to sea level that this will produce? My only other choice would be getting a machine shop to match the old one, because I couldn't find the original length nipple or any alternative after googling for a couple hours.

Also if anyone has had any success or failure in trying to change out this nipple (when it failed) and re-using the exhaust elbow and / or the mixing elbow let me know. I'd like to reuse those parts and send the new ones right back because they are over a hundred bucks each, but I'm guessing after 25 years the threads in the bottom of the cast mixing elbow may have gotten rather fond of the threads in the nipple, making them near impossible to separate, and to chase the threads in the existing exhaust elbow and/or the existing mixing elbow (if I could free the old nipple from them) I'd need metric tapered pipe taps right and left hand. And I so far can't even find any pipe fittings that size (besides the one specific Yanmar shorter substitute), let alone a tap.

 

[amcmahon]

J.Hunter, I had the same problen with my 1984 h27, only in my case the nipple actually rusted thru and the mixing elbow with exhaust hose separated. All this happened on my first real trip when I first bought the boat. In my case, I used a hack saw (the kind where the blade only extends out beyond the handle so you can saw inside the nipple) to GENTLY saw two groves in the nipple, about an inch apart while the elbow is held by a vise. You do not want to damage the elbow threads, although a few nicks in the therad will not hurt. The strip of nipple between the groves you cut can then be pealed out using a flat head screwdriver and hammer with the elbow in a vise. Once the strip is out, you can peal the rest of the nipple out of the elbow with the screwdriver. All this is really not hard to accomplish. The elbow can be sandblasted to get the carbon buildup out and checked for weak areas by a machine shop. The new nipple, by the way is usually a standard plumbing pipe nipple, I used a galvanized nipple, but you might find a stainless one. Good luck.

 

[J Hunter]

Update: amcmahon, mine must be different than yours because it definitely had a metric right hand / left haand nipple, not only not a hardware store item - simply undiscoverable by my fairly persistent eb searching. And even though I didn't re-use any of the threaded parts, nothing actually broke off.

Ended up using all three new parts, the exh elbow, the nipple, the mixing elbow. The bottom threads of the nipple were basically simply worn, eroded, corroded away as were the female threads of the exhaust elbow it screwed into, since the top of the nipple was still threaded into the old mixing elbow which was 20 + years old, rather than separating the unusable nipple from the mixing elbow to trying to use that one part, I simply went with all the new parts.

It was easy until the final connection to the engine. I decided to assemble the three steel parts first and then because of where the throttle cable was, attach the exhaust hose to the assy.and finally bolt it to the engine already attached to the exh. hose. Doing it from the engine back would have meant all the assembly while hugging the motor in the dark and nearly no room to spin the large water pump pliers I used to tighten down the pipe threads, and having to slide and twist and fight the hose over the mixing elbow outlet while it was stationary and having nearly zero clearance between it and the forward corner of the lazarette bottom deck.

It did take me a number of tries with the gasket dangling off of the bolts and the hose preventing me from easily squaring up and aligning the bolt holes and gasket face of the exh elbow/ engine exh, connection to catch a bolt and get it secured.

The much shorter new nipple also made the fat part of the mixing elbow /exhaust hose connection so close to the lazarette deck that I had to trim the corner of the plywood back about an inch for it to fit and not be in contact with the wood.

I guess I'm just going with the shorter nipple and throwing my caution to the wind about the mixing elbow being now much lower in elevation compared to the transom outlet. There is a silencer pot low in the stern between the two and the hoses plus the pot would have to fill up and get enough volume and head pressure to make it over the mixing elbow before flodding the engine with water. Since I'm a fresh water sailor mostly fairly close to my home port I'm going to just see how it does.