Exhaust reduction before water lock?

[BravoVita]

I have a 2" hose on my exhaust that feeds into an 1-1/2" water lock, the PO had a jimmy rigged connector on the inlet of the water lock to reduce it to 1-1-2" that I have to replace. I am planning on adding a Vetus exhaust hose reducer and a small piece of 1-1/2" hose to replace what was there but I wanted to get some opinions on if I might be missing something. I am sure there is a reason for the hose to be exiting at 2" and I am leaning towards an idea that for some reason reducing to 1-1/2" after a waterlock is okay but think reducing the hose prior to the waterlock might cause issues. This is a yanmar 2GMF

[NCboatrx]

The correct thing would be to replace the waterlock muffler with one for 2" hose. Also change the rest of the exhaust system so that you do not restrict the exhaust and cause problems with the engine. This is one case where the engine manufacturer knows a bit more about engines than either the previous owner or you.

[a64pilot]

I'll second the change to 2", exhaust back pressure is not good, we have too much already with the long run and having water mixed in and sometimes loops in the hose, don't add to that by reducing the size.

[Terra Nova]

3rd--stay with 2".

But 1 caveat...a client has a 2GM running into the original 1-1/2" system with no problem. If you're getting full rpm, it's probably OK.

[S/V Alchemy]

Originally Posted by NCboatrx

The correct thing would be to replace the waterlock muffler with one for 2" hose. Also change the rest of the exhaust system so that you do not restrict the exhaust and cause problems with the engine. This is one case where the engine manufacturer knows a bit more about engines than either the previous owner or you.

This is the correct answer. You have the right exhaust and the wrong waterlock.

[model 10]

How do you measure back pressure with a water lift system? It's the expanding gas that blows the water out not the engine. This is a little 2 cylinder engine, bet 1.5" is fine.

[foxfire]

You can measure backpressure by tapping off the system near the manifold and using a water tube manometer to observe the backpressure throughout the engine rpm range. Note that revving in nuetral does not produce as much backpressure as the same rpm when under load because the extra burnt fuel under load is converted to gas which increases the back pressure. Take the boat for a run to measure the true back pressure when under load. Compare that to the manufacturer's spec's for maximum acceptable back pressure and decide if any changes are needed. Incidentally when you pull the hose off the exhaust manifold elbow look inside for carbon build-up, Yanmars are notorious for almost blocking off the exhaust outlet with carbon, adding much more back pressure than a hose restriction.

[JOHNMARDALL]

Pretty good advice so far. Our recommendation is to take the engine's mixing elbow diameter as the minimum hose and fitting diameter throughout the wet exhaust system. Please let me know if you need any help configuring the system for your boat. Getting the water lock and vacuum-breaking air vent right is crucial to preventing back-flooding of the engine.
All the best
John Mardall
Vetus Maxwell Group

[TrentePieds]

Just going through this while replacing a Vetus with a Beta. The Vetus had 40mm (= 1 1/2" appr.) mixing elbow. The Beta is 50mm (=2" appr.). Changing the lot from the mixing elbow aft. The requisite parts are a small part of the cost of re-engining, and if you are handy [and a contortionist :-)] you can improve your installation for little cost. The less resistance in a diesel exhaust the better the engyne likes it.

TrentePieds

[BravoVita]

Originally Posted by JOHNMARDALL

Pretty good advice so far. Our recommendation is to take the engine's mixing elbow diameter as the minimum hose and fitting diameter throughout the wet exhaust system. Please let me know if you need any help configuring the system for your boat. Getting the water lock and vacuum-breaking air vent right is crucial to preventing back-flooding of the engine.
All the best
John Mardall
Vetus Maxwell Group

The whole reason we are here in the first place is a bad design to begin with, after splitting the Vetus because a there is a 1.7 millimeter difference between the 50 and 40mm replacement connector. I have emailed Vetus multiple times about this issue without ever receiving a response because your support does not exist. Emailing corporate to inform them of no response from support returned no response and calling sales resulted with a "so what do you want us to do?" I'm not surprised that a Vetus rep is not actually contributing something substantial to this conversation. I will be replacing the Vetus with a Beta (AND moving to 2" hose down the road without having to buy a new waterlock). I will be celebrating this headache being resolved with a ceremonial fire where the Vetus Waterlock will be burned to ash and sent back to the hell it came from.

[TrentePieds]

Quote: "I will be replacing the Vetus with a Beta"

Dang! Here I wuz thinking I could sell you a Vetus "ready for rebuild" at a good price ;-)!

TrentePieds

[BravoVita]

Originally Posted by TrentePieds

Quote: "I will be replacing the Vetus with a Beta"

Dang! Here I wuz thinking I could sell you a Vetus "ready for rebuild" at a good price ;-)!

TrentePieds

Or.. start a GoFundMe for burning that one too..