Mixing Elbow, where to buy?

[Nick F]

Sometimes that’s done to reduce exhaust back pressure. The less water the exhaust needs to push out, the less back pressure, so it’s not uncommon to divert some amount of water around the exhaust.

Thanks Bruce - I was not aware of that. I will keep an eye open on this.

 

[LakeMJim]

No problem, Bruce !

Of interest, the strange tee in the raw water line splits the flow coming from hex to the mixer. Part of the flow goes overboard above the waterline. A mechanic told me that this is a tell-tale so that you can look over the side and confirm the raw water flow. We have another 1974 GB42 with JDs in our club and it does not have this feature. As part of a raw water pump re-configuration I am removing the overboard lines.

This is a very interesting feature that we noticed when the boat was running, a steady stream of water shooting out. I assumed it was raw water used to cool the 'system' (not quite sure how it all works yet) but we had a momentary fear that it was the bilge pump (remember we had had the boat only for a day at the time).

But after investigating and talking to the surveyor we learned it is a rare but supposedly desirable feature.

Now, if that mixing elbow is the original from 1974, how bad can the design be?

(4600 hrs on the motor)

 

[LakeMJim]

Sometimes that’s done to reduce exhaust back pressure. The less water the exhaust needs to push out, the less back pressure, so it’s not uncommon to divert some amount of water around the exhaust.

This is exactly what we were told by the surveyor. He thought it was a good feature, but one he had rarely seen.

 

[GB42-424]

tap before mixing elbow

I have a mod bulletin from Grand Banks in my files issued in the 70's adding a tee for boats with 3" exhaust to reduce back pressure.

 

[MWelch2583]

My 6404s had a simple custom flange made that allows the use of Barr Riser 20-0039 and corresponding elbow

 

[LakeMJim]

MWelch: Your GB is very close to mine, which is 36-443

 

[RT Firefly]

Greetings,
Mr./Ms. MW. Welcome aboard. Nice solution in that custom flange.

 

[MWelch2583]

MWelch: Your GB is very close to mine, which is 36-443

Yea we are close, mine is a 74 as well. Picked her up before the start of last season and starting to chip away at her.

 

[stevensibs]

LakeMJim, i have a brand new in box stainless steel factory mixing elbow with weld bosses, my email is sjemery@gmail.com send me a note and I'll send you pictures and measurements.

 

[MWelch2583]

This is my setup all hooked up.

 

[dwiggl]

I see some kool ideas here. My thoughts are that if the part failed, It's going to fail again. Water and exhaust gasses are corrosive. May be best to put your energies to replacement, whatever the design.
Hats off to Marine Exhaust in Marysville WA. Last June, after 7 months of searching in 3 countries, I couldn't find a water jacketed part for my old Detroit D. It is a complex casting with a jog from the manifold to the turbo. I sent them the leaking casting, & 11 days from receipt - my new Stainless part was back in Maryland! In June no less! Fit perfect. Hats off to them. Worth every dime to save my cruising season.

 

[LakeMJim]

Finally installed

It was a long, slow, expensive process, as everything seems to be these days, but we have the new, custom made, stainless mixing elbow installed on our GB36, along with a bunch of other minor repairs (new exhaust hose for example).

Our first 2 shakedown cruises have revealed some other minor issues (all electrical as I predicted) but we managed to fix them on the water and didn't have to use our C-Tow membership at all. : )

Here are some pics of the finished product, hope it might help some others looking at getting this done.

 

[Nick F]

Jim - thanks for the update. Do you have pictures of the uninsulated elbow? Perhaps prior to installation. Do you have a sketch of the construction?
Thanks,
Nick

 

[LakeMJim]

Hi Nick,

No, sorry, these are the only pics I have. Because it was taking so long I went on a trip and only came back after it had been installed and tested.

We had some other work done and the whole thing was quite expensive for what it is, but we three are all resigned to paying the experts to do it properly as we do not have the time or desire to do it ourselves.

We had reduced our purchase price by an amount more than enough to cover this so it was less painful as a result.

As well, none of us had ever even heard of a mixing elbow before (I have always had Yamaha outboards, my partners owned sailboats).

Anyway, it's all done and we have had 2 nice shakedown cruises so it's all worthwhile. Big trip coming up in June,

Overall, love the boat, very stable in rough seas, compared to what I am used to.