Recommendations for Perkins 4108 Mixing Elbow?

[Doug Gibson]

When I bought my CD36 in 2005, I replace the riser/mixing elbow. The boat used the Yanmar elbow, so I replace with the same. Well, 13 years later, the raw water flow seems to be dropping and engine running warmer, so I suspect the raw water inlet in the mixing elbow is corroding up. So, time to replace elbow (and perhaps rest of piping). However, I never felt comfortable about the small 3/8" inlet size on the Yanmar elbow. It seemed undersized compared with what the inlet/strainer/pump were capable of delivering.

So - you CD36 owners out there, what mixer elbow have you used when replacing your exhaust? I see TAD has a couple that look like they would work, with 1/2" and 3/4" raw water inlet sizes.

Thanks,

[mgphl52]

many years ago I replaced the "custom" stainless mixing elbow/muffler on KAYLA's MD7A with a Yanmar elbow. In 2010 I replaced the elbow again with a Yanmar cast aluminum version. About 5 years later I bought KAYLA back from the folks I sold her to and one issue they had been fighting was low water flow & overheating. Before we sailed back from Long Beach MS to Niceville FL I changed the elbow to a stainless steel version and used a straight nipple for the water input instead of a 90 degree elbow. This has been working fine. I don't remember where I got the stainless version, but I suspect you can google it and find the site. BTW: the stainless version was cheaper than the Yanmar aluminum version!

[John Ring]

316-Stainless-Exhaust.gif

Exhaust-6.5-smal-lfile.gif

I rebuilt Tiara's exhaust using a 316ss flange for Perkins 4.108 from Transatlantic Diesel, and a bunch of 316ss pipe from McMaster. A bronze elbow into a T serves as the mixing elbow - flows like Niagara Falls.

John Ring
CD36 Tiara

[Doug Gibson]

Thanks John - I really like your approach. I also used 316 stainless pipe from McMaster Car when I last rebuilt. Can you tell me the size of the bronze fitting? Looks like 3/4" perhaps?

An unrelated question - looking a your second picture (bottom right corner). I see a "T" in what looks like your holding tank pump-out hose. The top of the T goes through the bulkhead. Is this the hose that goes to the manual pump and thru-hull? Mine is routed up through the top of the bulkhead, pass through close to the pump inlet.

The reason it caught my attention is that I will get a small amount of water collecting in the bottom of the port cockpit locker. There is no drain path until it gets deep enough to overflow into the engine compartment. I have been thinking about putting a drain hose through the bulkhead that would drain into the keel sump (rather than engine sump). Looking at your picture, I thought perhaps that is what you've done.

Thanks again for your response and pics - very helpful.

[John Ring]

Hi Doug,

I forget what size elbow I used for the elbow. I’ll have to measure it.

And yes, I added a T to the pump out line, running up to a vent loop, and down to a diaphragm pump before a thru-hull. No reason you can’t add a drain to your locker, just keep it very small, as any opening into the hull is always a safety concern if you take big waves with locker open or lid missing.

Best
John Ring
CD36 Tiara

[Restless.cd40]

On Restless I have replaced the exhaust elbow and mixing manifold three times. Original corroded away while cruising in Maine. Replaced with black pipe. Also corroded after a few years. Then replaced with stainless pipe and it’s been good for over 12 years. Except:
1. The engine vibrating caused the lower elbow to loosen and leak slightly. My thoughts were that the length of rubber hose joining to the water muffler was too short. So
2. I increased the length of the vertical pipe to about 14”. The hose now is 8”. The assembly was tightened very tight. The assembly is massive like the posted photo. Now then
3. The lower pipe joint is loose again but not before vibrating the nuts off the exhaust manifold joining the cylinder head causing loss of fresh water coolant and engine overheating. Admittedly the nuts did not have lock washers but still I believe the thing is too massive to be attached this way.

I’m open to question and suggestions. Pictures to follow.

Ted

[John Stone]

Egads, what a PITA. I must have lost my mind to install an inboard on the Far Reach....

[mgphl52]

Egads, what a PITA. I must have lost my mind to install an inboard on the Far Reach....

Too funny!!! Just go electric and carry a portable genset???

[John Stone]

Egads, what a PITA. I must have lost my mind to install an inboard on the Far Reach....

Too funny!!! Just go electric and carry a portable genset???

I considered that very thing. Too many limitations for the cost.

[Matt Cawthorne]

The 'mixing elbow' on my boat is about 38 years old. It is a bronze pipe nipple brazed into a piece of what I believe is black iron pipe. I changed out a few pieces of the exhaust riser a few years ago when I rebuilt my engine mount to acommodate the new placement of the muffler. The attached picture is the best record of what it looked like before I installed the new engine mount.