water flow through muffler and piping

[lr172]

This is my first post. I bought an '85 Hunter 34 this spring and doing a bunch of maintentance before launch. 3GMF engine.

After reading some suggestions about cleaning the heat exchanger (p/o mentioned overheating when run at WOT), I put a hose on the seawater inlet of the heat exchanger and poured some CLR in and let sit for an hour. Then I poured in a bunch of fresh water to flush it. To my surprise, nothing came out the back of the boat. I foolishly kept going until water appeared in my air filter :cussing: The hose I was using to fill it was well above the engine level.

I fiinally pulled the exhaust line off the mixing elbow and undertook the job of pulling the injectors and purging the engine of the foreign fluid. I was able to get it all out.

The odd part is that no matter how high I hold the exhaust tube, the water will not come out the back of the boat. If I blow on it, it will purge so it is not obstructed. I am guessing there is a loop or high spot back in the stern area that I cannot see. I hold the hose as high as it will go (top of valve cover) and fill the hose full. It holds this water and doesn't budge.

Is this normal? I thought more about it on the drive home and thought that maybe the exhaust pressure may force it out, but was worried that the standing water would seep in again upon shutdoow. I am quite competent with engines, but this is my first inboard-based boat and have never worked with a mixing elbow before. The engine ran fine for the P/O and shows no signs of problems. I don't think the injectors had ever been out before.

Hoping someone can provide some guidance and suggestions for resolving this.

Thanks for any help you can provide.

Larry

 

[kloudie1]

Water Flow Stuff

Welcome aboard, Larry.. !! Lots of good folks here and many Hunter 34 folks to get comments from. There is a loop that goes up several inches above the engine. You can see it way aft behind the battery box in the starboard cockpit locker. The engine exhaust gas pumps the water over the loop when the engine is running. BUT remember that if you crank the engine a bunch without it firing, the water will back up into the engine just as you've seen. You can clear it by using the decompression levers after the water inlet valve has been closed or the hose removed from the injection elbow and the elbow removed and the air cleaner removed.. Hand turn the engine until the water is all clear.. re-install the exhaust ell at the rear of the manifold (4 bolts).. drain the exhaust hose before re-installing on the elbow. Turn the engine over very slowly by hand through the compression strokes of all cylinders.. Then remove the mixing elbow water injection line and put it in a bucket.. Crank the engine very briefly to clear the exhaust hose then re-install the injection hose.. She should be fine. Why yes, I did water lock mine while trying to bleed the diesel pumps.

 

[Steve Dion]

Overheating is just as often created by the vessel not having a the proper propeller. Assuming you can start the engine and purge all of the water out of the system, I suggest that you properly remove the mixing elbow and check it before you do any potential damage.

These engines are no longer in production. If you damage the engine you will be looking at a very expensive rebuild or replacement which can be $10k-15k.

There have not been any posts that I can remember that would indicate that CLR would correct a problem with carbonization of the mixing elbow.

Best of luck, but I would hire a professional if you really don't know what you are doing.

 

[robertsapp]

I'll bet that's one mistake you'll never make again. So, yeah, there will be an elevated loop in the exhaust hose back there, the purpose of which is to keep water from being pushed into your exhaust by a following sea and flooding your engine. It will be high enough to be above the water level at the maximum normal angle of heel. Higher than your engine for sure. So when you were pushing fresh water into your heat exhanger, it was running through the exhaust elbow and back into the engine, since that was lower than the exhaust loop. As Kloudi1 mentioned above, that's also why you need to close your seawater thru-hull if you 're going to be doing a bunch of cranking, like when purging the hi pressure fuel lines. If you don't, you'll end up flooding the exhaust and backfilling your cylinders with seawater. Anyway, pick up a copy of Nigel Calder's book on marine diesel engines. It's less than $19 on Amazon and will really help you understand what's going on back there. By the way, the 3GM30F is a great engine. Some say if you take care of them properly you can get over 10,000 hours out of them. Cheers.

 

[lr172]

Thanks for the help and for the tips about doing it again while cranking. Yes, it is definitely a mistake I will not make again. Wish I had thought about the decompression levers, as pulling the injectors means I have to wait to get new o-rings to put them back in. But at least I'll get some experience bleeding the fuel system now:dance:

Thanks again for the quick and thorough responses. It is much appreciated.

Larry

 

[Dan Johnson]

Larry...

Welcome aboard the Big Boat Forum and the home of many of us with H34's.

Claude put you on the right track.

Steve raised a good point: What prop do you have? The common one on H34's has been a two blade, right hand 15x12. A number of owners have changed to a feathering/folding, or even a three blade one. The overheating at WOT could be the early signs of a clogged exhaust elbow, a common problem with age.

Normal cruising RPM is around 2,600 (75% of max, which should be about 3,400). I can run all day long at 2,600 - 2,800 with a boat speed of 6.2 to 6.5 knots.

Cheers and good luck!

PS: Found a pic of the exhaust hose exiting the hull in my H34.

 

[Alex Dare]

On the plus side, you realized what you'd done and didn't try and crank the motor with the cylinders filled with water. That's a fun way to wreck some con rods.

 

[robertsapp]

Yes, any f@#! up that teaches a lesson and doesn't break anything is actually a blessing in disguise. Or, to put it another way, if you're not screwing up, you're not learning anything, you're just practicing what you already know.