While Sailing: Forward or Neutral Gear?

[ndutton]

With the diagram below, where/what should I do?

Move the blue water injection hose to the other side of the riser loop immediately (I'm hoping it's an inaccurate drawing).

[sastanley]

Rick, what Neil said..here is a pic of my 'in process' hot section. In this picture, I have no hoses installed, but there needs to be a vented loop between the manifold & the exhaust injection point. Mine runs to the right (out of the picture) and up into a the counter top above the water line, the vent is mounted there, and it comes back down to the bronze water injection fitting.

I know someone has to have a better picture with it installed..

[JOHN COOKSON]

Do you have a water lift muffler?
Here is a diagram for a Cat 27 hot section from Moyer. If you rebuild the hot section this way you won't have any problems.

TRUE GRIT

[rpowers]

Replies

Shawn- Excellent! I'll get an anti-siphon loop right away. And the flap, I've seen people install a white plastic/rubber flap on the outside- will do that too.

Neil- Yes, you are correct, my mistake- drawing corrected now above.

John- No hot lift muffler.


So, an anti-siphon loop and exhaust flap, coming right up!

-Rick


Below is a quotation from the Catalina Direct website regarding the exhaust flap:

"This is a nice retrofit for early boats which used a plastic through hull fitting and a piece of rubber flap over the port. The rubber flaps have long ago disappeared. This leaves the engine exposed to water intrusion into the cylinders in a following sea. Installation is from the outside of the boat using the three screw holes provided. You may still have to stand on your head in order to re-clamp the exhaust hose to the tube. Requires 3 #FAS549 mounting screws for installation. See below

[sastanley]

Rick..I updated your drawing some more!

[rpowers]

Thanks

Thanks Neil!

Yes, parts ordered!

Better chill on my speed sailing for a few days...

-Rick

[Dave Neptune]

Valve

Rick, a working anti syphon will probably fix you up fine.
I reduced the last 12' of my exhaust to 1 1/2" to aid exhaust "water lifting" performance for such a long run in my boat. I noticed no performance changes other than less water in the exhaust system. The valve is an 1 1/2 ball type mounted to the thru hull on the bottom of my flat transom about 20" above the water. I close it when going down hill and the water starts to come up to the overhang on the transom.

Dave Neptune

[rpowers]

Anti-Siphon

Great, thanks Dave N. How do you reach/access your ball/valve?

Also:

What exactly is the siphon that the anti-siphon prevents?

I've been trying to picture it, but I don't understand.

-Rick

[Mark Millbauer]

Rick,
I have the same boat and same exhaust set up with one exception and have never had the problem. I have no anti-siphon valve either. I usually sail with the transmission in forward gear as well. The exception seems to be a flapper cover on the exhaust thru hull.. That said, do NOT use the Catalina Direct thru hull. I did and seriously regret it. The metal flap makes an awfull racket. My original thru hull had a piece of obviously home-made rubber sheet metal screwed to it as a flapper and it worked just fine. In an effort to make things look more ship-shape I changed to the fancy one from CD and am sorry I did. I'm still thinking about a way to modify it three years later. I hate it and the noise it makes! Just listening almost destroys my boating experience!

Now that you know how I really feel, I suggest fastening some sort of rubber or plastic flap over your thru hull and giving it a try.

Mark
C27 4289

[sastanley]

Mark, I maybe said the same thing in my post, but thanks for clarifying...I did not like the Catalina Direct flapper exhaust thingie..I returned mine as well..

My boat currently has a 1 5/8" plastic thru-hull at the transom (matches OEM manufacture) with no rubber flap...I think there must be a rise above the waterline in the center of the boat to solve the exhaust backflow while sailing problem.

[hanleyclifford]

Before going to the "flapper-do-thingie" concept I would make every effort to maximize the vertical rise of the exhaust at the transom. Also moving the thru hull higher and more amidships can be beneficial.

[rpowers]

Rubber Flap

Great minds think alike!

I have some rubber sheet material (1/8"), with two plys of nylon fabric impregnated.

This material is found at my local hardware store, and is called "diaphram rubber sheet". I use it to make large gasket shapes for fuel tank hatches, etc.

I looked at my transom, and there is the plastic exhaust through-hull (no flap) and the old screw that used to hold the old flap.

Soooo...., I cut a 1 3/4" circle of this rubber sheet, fabricated a thin aluminum "part of a circle" to spread the force of the screw along a horizontal line across the whole rubber circle just above the exhaust hole, and fastened it in place.

I installed it this morning, and it works great! (at the dock). In other words, plenty of chance for cooling water and exhaust gas to escape, but it closes fairly tightly with no out pressure.

Half the battle is done. Next, the anti-siphon vent.

Again, any idea what siphon we are guarding against?

-Rick

[edwardc]

Next, the anti-siphon vent.

Again, any idea what siphon we are guarding against?

-Rick

Whenever the water injection point is below the waterline, the potential exists for a siphon to start. Most pumps will pass some water even when stopped, especially if they're worn.

This siphon will quickly fill the waterlift muffler and back up into the manifold. (your secondary defense against this is a tall hot-riser). If any engine valves are open, the water gets in.

By introducing an anti-siphon loop above the waterline, with a 1-way valve in the vent line, as soon as the water in the "downhill" portion of the line (between the loop and the injection point) starts to flow downhill under its own weight, the suction produced opens the anti-siphon valve and allows air in instead of continuing to suck water through the pump. Moyer's valve will open with as little of 1 foot of "head". This eliminates any possibility of a siphon starting.

When the engine is running, the pressure produced by the coolant pump keeps the anti-siphon valve closed. It only opens under suction.

Hope this makes it all clear!

[rpowers]

Thanks Ed!

Thanks Ed for that explanation! Very clear.

-Rick

[Dave Neptune]

The syphon

Rick the syphon break breaks the syphon that is created by the loop from the manifold to the exhaust. If any of it is lower than the water line a syphon can be created. I have seen it happen intermitantly on boats where it was just close to the water line, the right sea or an extra passenger and here comes the water.
My access to the shut off valve is at the transom and I have easy access through the lazerett.
Because I have absolutely no rise from my manifold to the exhaust I have gone to a manual valve I insatlled in my loop after removing the anti-syphon valve (which has failed to many times~~not enough height). Now I need to remember to open it when I shut her down. More than once since I've had the boat I have sucked to water off the bottom to get going. I even keep an oil and filter change onboard all the time.

Dave Neptune