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Water in Cylinders

RoyS

.
Jun 3, 2012
1,163
Hunter 33 Steamboat Wharf, Hull, MA
Tale of woe here. My Yanmar engine manual states that the idle speed should be 800 and to rev engine up just before shutting down to clear carbon out of the head. Never had a carbon problem and observed that my idle has always been 1000. Changed two things to bring on near disaster. First I adjusted my idle down to the recommended 800. Second I stopped revving the engine before shutting down. The other day when I tried to start the engine up all I got was a thunk. Checked voltage on start battery which was ok and tried again. Blew a 250A fuse on the start battery circuit. Good thing, that. Investigation found that the exhaust elbow and hose was full to the top with water. The engine was hydrolocked. Repairs consisted of removing elbow (in fine shape) and draining exhaust hose. Removed injectors, tied off decompression lever to hold valves open. Rotated engine by hand while blowing out water through injector ports with my portable nail gun air compressor. I had a dummy injector for compression testing that came in handy. After reassembly, all is well and no damage. The moral here is beware of slow idle that may not completely expel water in the exhaust system and be sure to rev up when shutting down to blow all remaining water out.
 
Feb 14, 2014
5,628
Hunter 430 Waveland, MS
From H33 manual...
EngineMuff33.jpg

Something does not sound right about what you suggested.

Your muffler should be below your boat's actual water level and the exhaust exit above that line.

Even idle speed should "spit out" the muffler water.

be sure to rev up when shutting down to blow all remaining water out.
That should make no difference. Water is still flowing in to quench exhaust.

I would check your oil for water.
Jim...
 
Jun 11, 2004
1,202
Oday 31 Redondo Beach
Something does not sound right about what you suggested.

Your muffler should be below your boat's actual water level and the exhaust exit above that line.

Even idle speed should "spit out" the muffler water.

That should make no difference. Water is still flowing in to quench exhaust.

I would check your oil for water.
Jim...
I agree with the above.

Also, you might want to search for and read up on anti-siphon valves (vented loops) for marine engine exhaust systems.
 
Jun 15, 2012
620
Hunter 50 AC St. Petersburg
Ran my engine at idle yesterday. Amount and force of water coming out of hull exhaust at 800 rpm would not support slow idle raw water issues.
 
Feb 14, 2014
5,628
Hunter 430 Waveland, MS
After thinking more about your issue @RoyS

Your muffler may be partially restricted or full of exhaust crud.
That would do the same as you described.
Jim...
 

RoyS

.
Jun 3, 2012
1,163
Hunter 33 Steamboat Wharf, Hull, MA
Thank you for your comments. All I know for sure is shortly after adjusting the idle down and with my neglecting to rev the engine at shutdown, I experienced hydrolock. Muffler is below waterline and the exhaust hose loops up and then down to the hull exhaust port. The cast iron exhaust elbow was filled to the top when I removed it. Height of water in exhaust elbow was way above waterline. No visible defects or clogging in elbow, just a thin coating of carbon soot. Appears ok now and splashes out when running. I will watch.
 
Feb 14, 2014
5,628
Hunter 430 Waveland, MS
The cast iron exhaust elbow was filled to the top when I removed it.
This means something is preventing Gravity from stabilizing water in the exhaust loop.
If clear, clean, and no engine running...

Static Water level in the that loop is almost the same as boat water line.

Maybe slightly less from last "Spit".
Jim...
 
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Jan 30, 2012
1,088
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
Idle speed/reving at sutdown is not the cause of this. Instead this happens if seawater overflows the waterlock, which means water backflows into the waterlock thence into the motor. There are two sources - the exhaust outlet or the seawater inlet (which is the seawater- pump - heat ex/motor - mixing elbow circuit.) So first verify the waterlock outlet cannot admit water from the exhaust outlet back into the waterlock.

Most likely is the second source. Make certain the seawater inlet loop - the section right before the cooling water to mixing elbow exit fitting - is as high as possible (above the waterline for sure) and that this loop has an anti-siphon fitting at the top.

Last - it is entirely possible the exhaust elbow internal separation structure (the casting section that keeps the water and exhaust separate) has failed - usually corroded away. This decay allows water into the motor via the exhaust valves before it spills into the waterlock. This threat is worse if you do not have an anti siphon loop. High revs at shutdown/higher idle will mask this problem but it is not likely you will be able to see this decay because these damaged separations are deep inside the casting.

Here are two articles: Designing a Marine Exhaust System - Seaboard Marine (sbmar.com) and Everything you Need to Know About Marine Exhaust Systems - Seaboard Marine (sbmar.com) Read and understand these and you will find the culprit.

A replacement goose neck shape mixing elbows are available here HDI Marine. Superior in every way to the factory version

Charles
 
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RoyS

.
Jun 3, 2012
1,163
Hunter 33 Steamboat Wharf, Hull, MA
Interesting. My exhaust elbow is not shaped as an elbow, it is more a straight casting angled down from the flange attachment. I was able to examine the inside and the separating barrier was intact. No clogging inside. This casting was installed in 2019. I replace these every four years. The one I removed in 2019 was still serviceable and I have that in my basement. To drain the exhaust hose, after I removed the casting, I laid the hose flat against the hull and let the water run out into the bilge. No additional water entered from outside the hull. I had already paddled my dinghy around to where the exhaust exits and felt with my hand that the exhaust exit was clear. That exit is about one inch below the water line. The exhaust elbow was indeed full to the top when this happened and gravity did not cause the water to run out, even when the casting was disconnected from the engine. However, the hose after the muffler forms a loop that first goes upward and then turns downward to the hull exhaust port. I will examine this further, but I think that the elbow is still higher than the loop. If so then gravity most certainly did not cause the water to run out. This rear loop height will be examined closely next time I visit. At present there is no anti-siphon fitting on the seawater cooling hose above the elbow. The heat exchanger is significantly above all of these items. Now I will read the information Charles kindly supplied.
 
Feb 14, 2014
5,628
Hunter 430 Waveland, MS
That exit is about one inch below the water line.
The exhaust hole, in level seas, should be ABOVE the water line.

Maybe you are storing too much gear or beer in the Aft part of your boat.

The Exhaust Below water, presents other issues. From the H33 manual...
ExLoopH33.jpg


Jim...

PS: I looked a several pictures of H33 on the web and that port is above the water line.
 
Jan 30, 2012
1,088
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
If it looks like this (this one was modified) then make a change.

AboveWL.jpg


There are two versions. Yours is for a motor installation in a boat where the motor is well above the waterline like in a planning hull boat- not a sailboat.

The gooseneck version (aka the exhaust riser) is for displacement hull boats - like sailboats - where the motor position is much lower relative to the water line.

Displacemnt type.jpg


This riser type provides a loop above the water line. In addition water spill-over is well below the exhaust gas chamber - water exits on the discharge side of the loop. This design protects from back flows in a displacement hull install whereas the other one cannot.

Charles

Edit: ps. Based on your description of the tubing layout downstream from the waterlock, you definitely need the siphon break too.
 
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Likes: JamesG161
Dec 28, 2015
1,349
Laser, Hunter H30 Cherubini Tacoma
If it looks like this (this one was modified) then make a change.

View attachment 198388

There are two versions. Yours is for a motor installation in a boat where the motor is well above the waterline like in a planning hull boat- not a sailboat.

The gooseneck version (aka the exhaust riser) is for displacement hull boats - like sailboats - where the motor position is much lower relative to the water line.

View attachment 198389

This riser type provides a loop above the water line. In addition water spill over is well below the exhaust gas chamber - water exits on the discharge side of the loop. This design protects from back flows in a displacement hull install whereas the other one cannot.

Charles

Edit: ps. Based on your description of the tubing layout downstream from the waterlock, you definitely need the siphon break too.
I just installed a HDI elbow with exhaust manifold and coupler. High quality product at a reasonable price. Local too!
 
Jan 7, 2011
2,829
Oday 322 East Chicago, IN
The Exhaust Below water, presents other issues.
Jim...
My 1996 Hunter 280 had an exhaust exit below the water line. Never had any issues with it, other than I could not see water flow out the exhaust. After a while though, I could tell from the sound that I forgot to open the cooling water thru hull.

maybe you can see it in this photo….
9EC7A5AA-6D21-4243-BBCC-E95A8F27DC9A.jpeg


Just kidding (Well…maybe).


Greg
 

RoyS

.
Jun 3, 2012
1,163
Hunter 33 Steamboat Wharf, Hull, MA
Just back from inspecting my exhaust system. First of all my h33 is a 1980 version and the exhaust exit is below the waterline. The 2qm15 engine has a straight exhaust casting that is only slanted down. There are other designs available for this engine. After reading the info that Charles supplied this design is not a good one. The spill point on the elbow is only about four inches above the waterline. The exhaust exit on the hull is about one inch below the waterline pointing down. However the 2” hose connected there makes a large radius loop before going down to the muffler. The muffler has a waterlock. The spill point on the final loop is about five inches above the spill point on the elbow. If gravity were to act on the water filled hose without the waterlock the engine would flood. I have no idea how effective the waterlock device in the muffler is. This system design has worked since 1980. I still think the hydrolock was due to low idle allowing the hose to partially fill and my failure to rev the engine just before shutting down. That is not to say modifications are not called for. I think I will replace the large hose loop with a fiberglass elbow to limit some of the water volume in the hose. And I will look at applying a different type exhaust elbow. Thanks for all the good advice.
 
Jan 30, 2012
1,088
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
One more thing. Considering your exhaust terminal outlet is so low - review Tony's notes. See if you can have the last loop (the large hose loop downstream of the waterlock outlet) crest at a height lower than the water injection point in the mixing elbow. This means the terminal outlet has to be the lowest point in the large hose circuit. If you can do this then no matter what any overflow will drain overboard - and cannot backup into the motor via the exhaust valves.

Charles
 
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Apr 22, 2011
725
Hunter 27 Pecan Grove, Oriental, NC
My 84 H27 does not have a waterlock muffler, just a fairly small straight through baffle type muffler. The exhaust exist is at the water line normally and slightly below when it squats with speed. Do you think your waterlock muffler is original to the boat? They do hold a lot of water that could cause a back flow to the engine if the system is not designed for one.
 

RoyS

.
Jun 3, 2012
1,163
Hunter 33 Steamboat Wharf, Hull, MA
Charles, I am with you here. If I replace the large exit loop hose with a fiberglass elbow fitting and replace the engine exhaust elbow with the other yanmar model (stainless copy), and add an anti- siphon fitting I will end up with a gravity draining system. Have added this project to my Spring Prep List. Wish to thank everyone for their input.
 
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RoyS

.
Jun 3, 2012
1,163
Hunter 33 Steamboat Wharf, Hull, MA
Heritage, I have no idea if the waterlock muffler was original design. Must have been though as without it in my case hydrolock would occur every time the engine was shut off.
 
Feb 14, 2014
5,628
Hunter 430 Waveland, MS
Must have been though as without it in my case hydrolock would occur every time the engine was shut off.
Unless you have a restriction in your exhaust system.

By the way..
With your exhaust below the water, little need for a muffler.;)
Jim...
 
Jan 7, 2011
2,829
Oday 322 East Chicago, IN
What does a water-lift muffler do actually? I assumed it was just using water to “muffle” the exhaust noise as opposed to some other type of baffle.

I didn’t think it did much more than that…

96C05401-4C9B-41EB-9DE2-544A092F7B22.JPG

Greg