Universal M25 Exhaust Riser/Elbow Options

[Kenneth K]

Here is the support bracket I used. It mounts to the aft engine block hoist point (which I removed to mount the bracket while I had the manifold off).



The support bracket has to be attached to the block, NOT the boat as the boat frame "stays still" while the engine vibrates, rotates, torques relative TO the boat.

 

[Christian Williams]

My M25 had a different style riser, which didn't seem to lend itself to a support bracket.

 

[Prairie Schooner]

Thanks all.

Ours didn't come with a support, and had lived that way for 36 years. But it does seem like a lot of stress to put on the elements. That riser is a lot of mass cantilevered out on the pipes.

This E38 owner had a similar problem years ago: https://ericsonyachts.org/ie/threads/universal-5432-m40-exhaust-elbow.5412/post-76434
And this was ours:

Again, this was after the mechanic had taken all that apart and put it back together. One would think if it were that close to breaking they would have noticed it. Anyway . . . The one bit of good news there is that the bolts are likely not frozen.

It makes sense that the vibration differential between hull and engine makes the overhead a poor place to connect it. Ken, your solution looks like a good place to mount a support if I do put one in. What motivated you to put the support on?

@bigd14 That hump hose is interesting. Is it stiff enough to still offer some support?

Seaboard Marine has a number of pages with helpful information. This is one:

Proper Exhaust Bracing

Proper Exhaust Bracing

www.sbmar.com

Some kind of rubber buffer might make sense. Now that we've had it break, I feel like I should do something.
Any further comments, experiences, and insights are most welcome.

Thanks,
Jeff

 

[Kenneth K]

What motivated you to put the support on?

Just the "physics" of having the weight of all that metal, plus 2+ feet of hose, plus water, all hanging cantilevered from a piece of 1.25" steel pipe. It's obvious where all the forces concentrate.


By the way, that short piece of 1.25" pipe screwed into the exhaust flange comes in two thicknesses, sched 40, and sched 80. Sched 40 is just too thin and won't stand up to the forces.

 

[bigd14]

That hump hose is interesting. Is it stiff enough to still offer some support?

No, it’s made of silicone rubber and is pretty soft by design to allow it to flex. It doesn’t fully solve the issue like Ken’s bracket does, but at least it’s helping to isolate the engine from the boat. I added it to address a manufacturing issue with the lift muffler. I had one made of stainless steel with different inlet and outlet sizes because I was unable to remove the existing bronze exhaust thru hull without major destruction and the old muffler had a broken inlet. Unfortunately the manufacturer didn’t leave quite enough space to clamp the hose on the inlet due to a gusset they had welded to reinforce the pipe section so I was worried about a hard exhaust hose working off with the engine vibrations. I removed as much of the gusset as I felt comfortable with, added the hump hose and all has been well since.

 

[Kenneth K]

OTOH: This was the original monstrosity of a riser/elbow many M-25 diesels had from the factory. I think it weighed 9lbs, all supported solely by the 1-1/4" pipe nipple without any support brackets. And this lasted 32 years:

 

[Odelay]

Hello all, I have replaced my riser with the yanmar elbow, but I can't for the life of me figure out how to secure the hose clamps on the exhaust hose that attach to the pipe under the lazarette. Ericson seems to have made this connection before any of the other wires and hoses were installed and I can't figure out how to get two hands on the end to get a wrench or screwdriver on the clamps.

Anyone have any advice???

1987 Ericson 34'
I went all stainless, everywhere online and my local shops said the OEM risers are no longer being made, so Yanmar elbow seemed the best option.

Thanks!