Exhaust riser inlet

[bayhoss]

At the time of purchase my E28 (Universal M12) had the raw water line that leads to the exhaust riser in the vertical position (green hose). Can anyone think of any harm that would be done by rotating the hose fitting 90* so that the water drained away from the riser?
Thanks in advance,
Frank

 

[Emerald]

If I am following the hoses correctly (and I'm assuming what's going on at the top where the picture cuts off) I think this hose has been routed above your water line to prevent a siphoning effect. Am I correct that it comes off the manifold and goes up out of the picture to the highest point possible in the engine compartment and then down to the mixing elbow? If this is the case, I'd leave it as is.

 

[bayhoss]

Thanks David, It does go up to the highest point. My concern is that the vented loop in the line will allow the water left in the line to gravity feed into the engine. Would it be more prudent to lower the lines so that they cannot drain into the engine? The vented loop should stop the siphon from happening.

Best Always,
Frank

 

[Emerald]

With the caveat that I don't have hands on experience with an M12, any water that ran back through this line should just be running in to cooling passages. It would be water backing in through the exhaust (e.g. water lift muffler filled and back flowed) that would be the common source of water working back into the engine. If this doesn't make sense, let me know - also, any chance you have a manual with a cooling circuit diagram? I think looking at this would verify that you're OK.

 

[bayhoss]

Thanks David, the raw water did find its way into the engine and turned the oil slate gray. I think the issue is with that darn mixing elbow. I going to replace it with an insulated pipe and use a TY fitting to intoduce water into the exhaust

Best,
Frank

 

[rwthomas1]

If the raw water in the hose dumps into the mixing elbow, it comes out usually right at the elbow outlet via a split/separator in the elbow itself. The only way raw water would get back into the exhaust is if it drained out of the elbow, into the wet exhaust hose and then backed up into the exhaust side of the elbow. Make sense? Looking at your pic it appears that the hose from the mixing elbow runs uphill to the waterlift muffler? If so, that would be your problem. The remaining water in the system is designed to drain to the waterlift muffler and be trapped there. IIRC, Centek/Vernalift specs a minimum 12" drop from exhaust outlet to muffler.

RT

 

[bayhoss]

Rob, thanks for the help. I'm repiping the system this weekend. You can bet there will be a full 12" of drop in that line.

Best,
Frank

 

[joe-fran]

WHile my knowldge of cooling systems pales in comparison with the other posts on your problem, I can add this tidbit. I have the same boat (E-28) and engine (1987). Last weekend I was changing out most of the cooling hoses on the engine (just because they were old and probably original). One my boat, the vertical green line you refer to goes as far up in the engine compartment and then returns down. However, at the top of the circuit is a brass fitting with a third small hose leading aft and going to a thru hull fitting beside the main exhaust outlet. This outlet sends a small but steady stream of water whenever the engine is running. I don't know if this helps or is just 'old news' to you guys.

Good luck this weekend

Joe

PS this is my first spring with the boat having bought her last July and I am working hard to get my engine compartment as clean as yours!!!!!

 

[Rocinante33]

What Joe is describing is an anti-siphon device, AKA a vented loop. It is a very good thin to have in the water line (at the highest point) because it can prevent water from siphoning up into your engine and flooding it.

Here is a link describing the function;
http://www.forespar.com/onlineCatalog/2009/Marelon/marelon_ventedLoops2009.shtml

 

[bayhoss]

Much better now thank you!

Joe-Fran, thanks for the help! I have the anti siphon in place and its working like it should. And, I'll wager that your engine compartment looks just fine. Too bad we can't get all the 28's together sometime! What caused the problem was the difference in height between the exhaust outlet and the muffler inlet. 2X thanks to Rob for the help! I made some changes that give a full 14" of difference. I'll post pictures of the changes ( just for you guys I'll go to the marina and mess with that darn boat. But, just this one time - ok!).

Best always,
Frank

 

[bayhoss]

Not better - sicker that heck

I thought I had this thing beat when out of the blue the engine oil re filled with sea water. The exhaust line is sloping down and there is 14" difference between the exhaust outlet and the inlet of the water lift muffler. I checked out the riser by running a hose thru the inlet and it didn't seem to leak water into the engine imput side of the riser. What the heck am I missing - I have a vacuum break that is working like it should. I can run the engine for an hour without any problem and then all of a sudden without warning the water backs up. I know that the photo shows considerable curvature in the exit line, but in reality it isn't that great.



Best,
Frank

 

[bayhoss]

Much, much better than new

As it turns out there was no issue with the exhaust system at all. There was however, one heck of a problem with the raw water pump seal. For the benifit of those who have the Sherwood pump, it is imperative that the small hole(s) at the bottom of the pump body are clear and open. If the seal goes bad and the holes are open, then the water drains out thru those holes. If the holes are clogged then the water is pumped straight into the engine. Bad things happen - oil and water don't mix.

Best always,
Frank