Poor exhaust system design?

[Waterant]

Was this exhaust system designed by morons or my simple mind is missing something?

while disassembling the port engine, which was damaged by water that got inside i noticed the muffler is full of water up to the entry pipe (see the image)
any small wave action and a lot of water will go into the turbo and the engine.

how is it possible for Mainship to build hundreds of boats with the exhaust system designed this way? how many engines got damaged because of this?

Or I'm missing something and on Mainships the water does not flow down inside the 6" pipe for some magical reason?

has anyone modified the exhaust system specifically on Mainship 430 with Yanmars 6LYA engines? is there any after-market solution or the custom-designed and made raised elbows is my only option to fix that?

 

[DavidM]

I can't make sense out of your pic, but my 34T had an equalization line that kept water from building up in the muffler. It used a port, available on many lift mufflers, at the bottom of the muffler which connected to a 1" hose and then out to a thruhull near the water line.

That equalization line assured that water couldn't build up past the port location. But you need the right geometry for this to work. Don't know about yours.

As another solution, it does look like you have room over the high point of the exhaust riser to raise it higher. Tony Athens and others recommends at least 12" of clearance above the water line. I did this on my Pilot 34 by welding an extension to the dry riser which raised it from 8" to 16".

David

 

[Keysdisease]

What David said, and there are other options as well. An exhaust flapper can also add some protection.

I will note you vessel is 20 years old and may not have had any backflood issues

 

[mvweebles]

No direct knowledge of Mainships, but you may want to ping Marine Exhaust Systems of Alabama. They've been around for years and may have drawings to fabricate something fairly easily. Still not inexpensive.

Exhaust should be as high as possible before water injection. If I read your picture correctly (I too struggle to capture the nuances, though edit showing waterline helps), I doubt this installation was kosher with Yanmar and likely would have voided warranty.

Good luck

Peter

 

[rslifkin]

That riser design is scary too, as it's injecting on an upward and horizontal area, so if the water injection elbow fails, you'll get an engine full of water. I'm also not sure what kind of muffler you've got, but most water lifts I've seen don't have the inlet at the top like that.



Personally, I'd be considering re-doing the whole setup to a safer design.

 

[Porgy]

I’d look at the installation manual for the engine and peruse some water lift muffler installation instructions. I’m looking at the Centek Vernalift instructions (seems to be a ubiquitous brand) and it calls for a minimum 12” drop from the exhaust elbow to the top of the muffler. There are some other key dimensions depending on the engine boat layout with regard to the waterline.

I’d also look if the seawater hose has has an anti-siphon loop too.

I don’t have that boat or model Yanmar but on both the Yanmars I’ve had, the exhaust exits the manifold, turns 90° up, then 180° down where it meets the exhaust hose which goes straight down then toward the muffler. The seawater hose meets near the top of the u-turn where gravity assists it going straight down.

 

[mvweebles]

Good article from Northern Lights that is common to most marine installations, not just their generators. Steve D references this frequently too -

https://www.northern-lights.com/media/PDFs/misc_pdfs/dont_drown_me.pdf

Picture below is extracted from the article. Differences are hieght of exahust manifold relative to waterline.

Peter
EDIT - Steve D article
https://stevedmarineconsulting.com/wp-content/uploads/2014/03/ExhaustSystems170-FINAL.pdf

 

[Pete Meisinger]

I don't see an exhaust hose coming out of your muffler. Is it located high or low? Also of concern is the nearly flat exhaust run from your turbo.

pete

 

[porman]

Yanmar exhaust

I have the same boat, same engines. Your picture shows the starboard engine and exhaust. Here's a picture of my starboard exhaust. You can see that the hose runs downhill from the elbow to the muffler. It appears the inlet to your muffler is at the top and mine is down a ways. Is it possible someone has replaced the muffler? The hose on the port side also runs downhill. My exhaust outlet on the side of the hull is halfway out of the water and the tube inside the hull is pretty much horizontal, so there shouldn't be a lot of water in the muffler.

 

[Waterant]

Thanks, guys. Really helpful.

The boat is 20 years old but has very few hours on the engines. Looks like the water got inside port engine after 300 hours seizing it before it was even broken in.

. Is it possible someone has replaced the muffler? The hose on the port side also runs downhill.

Could be. My port exoist looks line yours with entrance a bit down but this seems to be right at the waterline and not enough rise before the turbo.
Also, raw water injection on your picture seems to be on the vertical part ignoring gravity like on mine.

And the water damage is also on the port engine so it's possible the higher location of the entry tube on starboard engine is actually safer.

When I was winterizing the engines, I opened up the port muffler and it was full of water up to the bottom of the entry hose. even a small wave would send (probably sent) gallons of water into the turbo and beyond.

Very frustrating. My previous 1987 Defever made in Asia had a properly routed exoist. How come US made 2002 Mainship has this f*ed up that bad?!

I'll go prepare another few boat dollars to pay for a custom exhaust elbows for both engines. At lease there is some room to properly raise it higher.

 

[Arc]

I would take that shower head off and deep six it. That is the worst place to inject water.

 

[porman]

port exhaust

Here's a picture of my port exhaust. My engines have almost 2200 hours with no problems. However it is kept in fresh water with occasional trips out in Puget Sound and Canada. I did notice that my starboard side seems to be more vertical than yours, with the top of the elbow closer to the bottom of the stairstep.

 

[Waterant]

Here's a picture of my port exhaust. My engines have almost 2200 hours with no problems. However it is kept in fresh water with occasional trips out in Puget Sound and Canada. I did notice that my starboard side seems to be more vertical than yours, with the top of the elbow closer to the bottom of the stairstep.

Thanks. Do you drain muflers for winter?
Because the mufflers are full of water, does not seem like a good idea to keep water there for winter. but the drain screw is super small so it's not possible to put a valve with a hose routing the water somewhere so water goes everywhere including under the tanks.

 

[porman]

We use our boat all winter. The water it sits in never gets near freezing so no need to do any winterizing. I keep a bilge heater in the engine compartment just in case the temperature drops.

 

[Comodave]

Thanks. Do you drain muflers for winter?
Because the mufflers are full of water, does not seem like a good idea to keep water there for winter. but the drain screw is super small so it's not possible to put a valve with a hose routing the water somewhere so water goes everywhere including under the tanks.

It is easier to drain the mufflers before winterizing because you will save on antifreeze. The water in the muffler will dilute the antifreeze. We didn’t have a lot of water in the mufflers in our last boat so we didn’t try to drain them. But we did test the exhaust with a refractometer to make sure the antifreeze wasn’t diluted too much. We tested every single thing we winterized to make sure it was good to at least -20 degrees. When we first saw color in the exhaust it was only good to +30 degrees, so not much good in winterizing if you only go to +30.

 

[Derek]

Things that make ya go hmmmmm. I’m wondering if this may be the reason my starboard transmission cooler is dripping water out the open hose connection while my Heat Exchangers are getting cleaned and pressure tested. I just can’t figure out any source. It’s about a quart a day.

 

[Waterant]

Things that make ya go hmmmmm. I’m wondering if this may be the reason my starboard transmission cooler is dripping water out the open hose connection while my Heat Exchangers are getting cleaned and pressure tested. I just can’t figure out any source. It’s about a quart a day.

on this photo, you can see the water level in the port muffler. it's right at the bottom of the hose coming from the turbo
it will take just one idiot running close at full speed to get all this water into the turbo and the engine.

 

[firehoser75]

Tony Athens has lots of free info on marine exhaust issues, and he calls many of these exhaust systems as installed by the boat builder as "doomed to fail" (it is only a matter of time). Even the best quality components will deteriorate over time (salt water and high temps are a "deadly mix"). He talks about many engine rebuilds or replacements due to these exhaust issues allowing water to get into the turbo and beyond.
He is on the west coast and does build custom exhausts. I am sure there are others on the east coast as well. I strongly advise dealing with your exhausts now before you need "new engines". Get a professional you trust to design some thing that will work with your boat!
JMHO.
By the way, my former boat (a well respected builder), came with a "doomed to fail" design. This problem is very common, and in the worst cases can lead to very, very expensive repairs.

 

[DavidM]

On the east coast I worked with Just Right Auto and Marine in Wanchese, NC. I did the design and they did the fabrication of my exhaust extension. If you bring the boat to them, they will do both.

David

 

[chriscritchett]

+1 on the water injection elbow comments. Picture how they work - a pipe inside a bigger pipe, with water pumped in between - and then look at your system geometry. WHEN the inner pipe starts to leak, and it will, your SW pump is pumping its water into your turbo outlet. The muffler situation is weird, too, but this may well be your problem. If it isn’t now, it will be eventually.
Best to get new risers made up with water injection on the downhill side, well away from the engine.
And like everyone said, Steve D. & Tony at SBMAR.com have great articles on these issues.

 

[Waterant]

This problem is very common, and in the worst cases can lead to very, very expensive repairs.

tell me about this. i have another thread about removing seized port engine damaged by water which probably got there from the exhaust.
I'll not be comfortable using the boat until this is fixed because removing and rebuilding an engine is a time-consuming and expensive exercise. not fun at all.

I already talked to the guys at Marine Exhaust Systems of Alabama about this. They asked for more pictures and dimensions which I will do the next time I'm on the boat.

I will read SBMAR.com articles and talk to Just Right Auto and Marine in Wanchese, NC maybe they already upgraded the same boat/engine combination before and can at least provide a quote.

Thanks all for the info.

 

[Pete Meisinger]

I never drain either of my lift mufflers, either on the engine or genny, I always assumed that the antifreeze I run through the system lays in the muffler over the winter.

pete

 

[rslifkin]

I never drain either of my lift mufflers, either on the engine or genny, I always assumed that the antifreeze I run through the system lays in the muffler over the winter.

pete

Same here, although if I could easily drain the mufflers I might do that and need a lot less antifreeze. Or even drain the whole raw water side of the system and skip the antifreeze. Half of what I use every winter is just for the 2 main engines.

 

[Steve DAntonio]

Virtually every engine manufacturer specifies the minimum angle of the injection nozzle where it attached to the hose. For Deere it's 25 degrees, Cummins 15 degrees. Without researching it I don't know what Yanmar's requirement is but if it's less than 15 degrees it would worry me. My person rule of thumb is the water lift muffler should be no less than 12" below the injection elbow, too. More here https://stevedmarineconsulting.com/wp-content/uploads/2014/03/ExhaustSystems170-FINAL.pdf

In Taiwan, but homeward bound...

 

[Comodave]

I never drain either of my lift mufflers, either on the engine or genny, I always assumed that the antifreeze I run through the system lays in the muffler over the winter.

pete

I didn’t drain my mufflers when we used to winterize. Just added more antifreeze until it tested good out the exhaust. It may have cost a couple of more gallons of antifreeze but it sure was simpler.