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Date Posted: - Monday - 06/27/11 - 12:55pm
Author: Randall, Murre, M31 Hull #150
Subject: Engine Exhaust issue
Author: Randall, Murre, M31
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Subject: Engine Exhaust issue
During her passage from Mexico to French Polynesia, Murre had engine problems.
In brief, I didn't even attempt to crank the engine for the first week of the cruise. When did, she started very rough and there was moisture in the engine. (better documented in the blog, if interested)
Diagnosis was that sea water was being flushed into the engine via the exhaust. The through hull for the exhaust over-board is just inches above the water line (standard for mariners?) and the piping to the aqua lift muffler is a straight shot with no rise or sea cock or any other way to keep water from back-flushing into the aqua lift and from there into the engine.
Even after a brief, four hour passage this week in rough seas (20 knot winds on the beam) from Ua Pou to Nuku Hiva, the engine started roughly. So, the ingress of sea water into the engine takes very little time.
THE QUESTION: How to fix this? Has anyone "re-piped" their exhaust, adding in a sea-cock to shut off water OR a rise and siphon break? I'm not sure I can get the needed parts before arrival in Tahiti anyway, but I have two more passages of 2500 miles to make before getting home, and so would like to solve this problem sooner than later. The area makes accessing a sea cock once installed challenging, and ... well, am not sure what to do, so interested in any solutions that have been put into place.
Thanks in advance,
RR
Aboard MURRE
Nuku Hiva, Marquesas Islands
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Exhaust issue -- Mark, AEOLUS M31, - Monday - 06/27/11 - 2:33pm
Hey Randall, great to hear from you, I like I'm sure a lot of fellow Mariner's have been following on your blog, GREAT writing! I'm glad to here the engine problem is external. Believe it or not on my boat the aqua lift muffler and the piping from there aft are PVC. A south african showed me his PVC "Y" muffler about 25yrs ago and it works great on the old 4.107. A short piece of exhaust hose is between the muffler and the 1 1/2 PVC pipe that runs vertically up to the under edge of the lazarette hatch. From there it turns 90* and runs the length of the opening of the hatch where it turns 90* down again. One more 90* turn to line up with the thru-hull (that as you say is just above the water line) and attaches again with a piece of exhaust hose. So 3-90* and 1-45* used to turn from the muffler up vertically.
It's worked for 25yrs, and goes without saying that it CANNOT be run dry, but I have always shut down and fixed any dry run problem immediately, impeller or stainer.
A fiberglass pipe would be better, but with your location you might consider a version of my layout.
Fair Winds Mark
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Nuku Hiva -- Lawrence Killingsworth M40 Ta' Ata Ori, - Monday - 06/27/11 - 4:01pm
Sorry to hear about your engine troubles, Randall. I don't have any mechanical advice for you, but I just wanted to comment on how much I am enjoying reading your blogs from your sailing adventure. Well done and much appreciated by those of us back here on the mainland.
Back in the late 70s, Ta' Ata Ori was dismasted (main mast) on her way from Mexico to the Marquesas. She limped into Nuku Hiva, where local craftsmen helped the owner at that time to build a mast out of island wood and re-step it, using the crane from a trading steamer. I have pictures of the whole process. So, just to say, your exhaust may be goofy, but at least you made it into Nuku Hiva with all your masts.
Best of luck with the rest of your voyage and thanks for taking us along.
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Syphoned loop -- Paul M31 #106 NJ, - Monday - 06/27/11 - 8:47pm
On Guillemot I have the exhaust, after being pushed out from the waterlift muffler, going straight up to the underside of the port cockpit seat, where it is connecte3d to 2 90 degree elbows thus forming a fairly tight "U" and then it comes back down to to another 90 elbow and is lead aft, starting slightly higher than the exhaust through-hull which is in the same location as you describe, a few inches above the water, on the underside of the hull. The line basically runs on the underside of the locker (false) floor.
On the other side of the water lift muffler, the raw water injection fitting onto the injection elbow is outfitted with a "T" - the main direction being to the injection elbow (downward), but also allowing for a 1/4" nipple to point upward, to which a plastic 1/4" line is connected. This 1/4" line runs along the exhaust lines up to under the cocpit seat, but then comes through the cockpit wall, runs down the side of the cockpit well to just above the portside cocpit drain, in which it squirts. This little line serves two purposes - 1) one can instantly see water pressure, much like the "pisser" (for lack of a better word) on an outboard engine, verifying water flow; 2) once you turn the engine off, the little line instantly breaks the vacuum (one can hear noticable "gurgling" going on)and thus prevents syphoning and/or back flow into the waterlift muffler, ultimately into the exhause manifold..
The top of both loop bends are just under the seat as such well above the waterline and effectively prevents water flowing back.
As was stated earlier, some components in this system can be made from grey PVC - mine are, to the surveyor's shachrin - though most of it is either multi-ply rubber exhaust hose, galvanized pipe, or brass... All the PVC parts are on the exhaust side of the waterlift muffler.
I will try to post pics of the loop and the plastic vacuum break line...
Hopefully this helps a bit.
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Some pics... -- Paul M31 # 106, NJ, - Monday - 06/27/11 - 9:03pm
Main loop with 1/4" line showing going through the plywood into the cockpit well
Hard to see, but in top left corner you see the "T" at the injection elbow raw water inlet - with the small 1/4' line leading up...
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Thanks for the feedback -- Randall, Murre, M31, - Wednesday - 06/29/11 - 2:10pm
Mark / Lawrence,
Thanks for the comments on the writing. It's been a lot of fun keeping up the blog--a lot of work too--but fun. So I appreciate the feedback.
Lawrence, fascinating re dismasting and rebuild here. The Aranui 3 (twin crane steamer that visits the islands from Tahiti) is in port now. Wonder if that's the one that helped your Mariner step her new main. I posted one photo in most recent blog. Same ship?
Yes, am quite happy to NOT have lost masts in the crossing!
Aranui apparently means "great highway", and there has been an Aranui in transit between the islands since WWII, when the first Aranui was a PT boat. The company owner is Chinese and lives in my home town of San Francisco (found out recently).
***
Re the exhaust--thanks all for the feedback. Bruce on Gitana and I have been corresponding too (he actualy posted the original question for me...connectivity here is way too slow...). Feel like I have a much better idea of fix, including PVC materials if needed. Mark, thanks for the idea of usable parts I can find in the islands. Not sure if I'll get to this before Tahiti (August) but very good to have an idea of attack.
Best,
RR
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PVC it is...at least for now -- Randall, Murre, M31, - Saturday - 07/ 2/11 - 12:09am
Well, I think I'm going to give Mark's PVC option a try.
If I measured correctly today, the inside diamter of the exhaust hose I have is just shy of 2 inches and very close to 5 cm, which just happens to be the outside diameter of PVC I was able to find at the ONE local (15 minute row and 1/2 mile walk) hardware store. And they had four 90* elbows. And they had cement (though no primer). Amazing. Thought for a moment I was at Home Depot, except the staff was helpful, all six of them. And they understood me when I said or pointed to the French words I'd written in my note book, like:
Pipe--Tayua (not conduit)
Elbow-Cotes
Inside Diameter--Diametre Interieur
Glue/cement--Colle
Coupe--to cut (to a length)
It all worked in one go--at least as to aquisition of materials. Cost: $60 US.
This is going to look like a hack job, but all in the name of no salt water in the engine.
--
Am concerned about the heat issue. PVC is rated to 140*. I know Murre runs at about 180* But, Mark, if you've had this in place for years, then...
--
Plan to create one rise aft, near the through hull, for now.
--
Any last minute suggestions...? Will attempt this tomorrow...
RR
Aboard rolly rolly Murre
Taiohea Bay, Nuku Hiva, Marquesas
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Exhaust temp is much lower than engine coolant temp -- Paul M31 #106 NJ, - Saturday - 07/ 2/11 - 9:06am
The only influence the 180 degree engine coolant tem has on exhaust temp is at the water cooled exhaust manifold. The (dry) exhaust is cooled somewhat there but definately not all that much. The real cooling happens at the raw water injection elbow where the exhaust gets mixed with seawater after it is done cooling the heat exchanger, oil cooler and tranny cooler. Then the exhaust gases literally pushes the raw water from the water lift muffler into the exhaust line to the through hull - well cooled at that time...
The only downside I see with where you propose to put the loop is that, since the exhaust line is sloped down towards the thru-hull, you will have standing water in that hose from then on when the engine is shut off - instead of the hose draining as was designed. With my system, all hoses drain - either back into the water muffler or overboard, once I shut off the engine.
But it should help you keep the ocean out of your exhaust manifold for now.
Will you be able to also put in some vacuum break?
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Exhaust plumbing -- Mark Aeolus M31, - Saturday - 07/ 2/11 - 3:11pm
Randall, glad to hear you could find the needed parts that easily. If I understand, you're going to put the loop aft close to the through hull. On my boat the PVC lift muffler is attached to the lower front side of the fuel tank, so the water that flows back into the muffler when I shut down is minimal (just the vertical rise to the underside of the cockpit seat.) Just make sure that if your muffler is lower than the loop your installing there won't be more water backing into the muffler than it can hold when you shut down. Hope that makes some sense? Mark
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Job Done -- Randall, Murre, M31, - Sunday - 07/ 3/11 - 2:37pm
Thanks Mark and Paul for last round of advice.
Paul, on Murre the thru hull was actually AT or ABOVE the Aqua Lift muffler. (Done so before I bought the boat and in all these years I didn't catch the problem--worthy of ridicule: both the install and my failure).
Per your collective suggestions, I did move the rise forward a bit. So the run forward of the rise is now roughly equal to what it was before I added the rise, maybe a little less.
Though I measured THRICE, the exhaust hose was not 5cm ID as the OD of the fiberglass elbow going into it from the Aqua Lift suggested, but was ¼ inch or more smaller. (Not discovered as such until the hose was cut and I was thus beyond the point of return. This represents some sort of universal law that I wish we could repeal.) So, spent most of my time fashioning plugs to drive into the steel reinforced hose to expand it. One hose clamp is all I could fit on either side. Unfortunately this is the weakest part of the install, but I’ve tugged pretty hard at these connections and they’ve not budged.
The rest, cutting and gluing, was pretty straightforward. Whole job held in place with zip ties for now--all I have. But is solid.
Providentially, I happened to find a small piece of flexible ***PVC*** hose at the side of the road while walking back from the hardware store with my PVC pipe, which I have added to the top of the rise as a siphon break (cemented in place). Have run it for now into the cockpit where it dribbles a tiny bit of exhaust water when the line is under pressure--indicating water is passing through the exhaust hose without my having to lean over the stern.
Ran the engine for an hour and all appears to be well. To your points re heat issue, PVC was warm to the touch after an hour, but just that, so, was well below the 140* rated temp, I’d guess.
Real test will be the 450 mile run to the Tuamotus coming up in a couple days.
Pictures here: http://www.flickr.com/photos/63439824@N04/sets/72157627107299856/detail/
Thanks all (inluding Bruce, with whom many emails) for the feedback.
RR
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Tuamotus -- Lawrence Killingsworth M40 Ta' Ata Ori, - Tuesday - 07/ 5/11 - 1:02pm
When you get over to the Tuamotus, Randall, make sure you stop at Rangiroa Atoll. I was there a couple of years ago, on the brigantine Robert C. Seamans. The snorkeling in the lagoon is marvelous, you can sip a cold brew in the on-the-water bar at the Kia Ora Resort and you can even pick up some black pearls for your BWW. Happy sailing!
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