This has been bugging me for several years, the exhaust through-hull is right on the waterline. The Yanmar engine manual recommends at least 6" between the waterline and the exhaust. When motoring, the stern dips 6" completely submerging the exhaust by an inch or so. Should I be concerned? Anybody else have this problem? Cheers, James
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Background on WHY the thry hull is so low
James, I learned the hard way that there is, according to a sharp mechanic at Sherrill Marine in Avalon, Catalina Island, CA, "a significant design issue with the raw water cooling systen on the V32". Here's the scoop, and a little "color": wife Dede and I were moored at Hamilton Cove, in Avalon's outer harbor beginning Friday morning, October 11. We were there for the weekend to a) celebrate Dede's birthday b) participate in our yacht club's cruise c) attend the Jazztrax an annual jazz concert. (We've been attending Jazztrax for past 9-10 years - it's a great event and the Avalon Ballroom where it is held is a stunningly beautiful venue.) Well, the weather was beautiful all weekend but the outer harbor was quite rough, with 2-4 foot swells coming almost accross the port beam. Sunday morning I decided to start the engine and charge up as the Harbor Master had just come by to say we could, at last, move inside. When I attempted to start the engine using just the house batteries and it would barely turn over. Strange, since I still had 12 volts+ on the meter. Then I engaged the dedicated starting battery and woe-of-woes, there was no improvement! This was indeed VERY strange (and I was thinking, probably very expensive also) as now meter be damned, I KNEW I had lots of juice. Because I'm not in the least mechanical, I then called Vessel Assist. But even with their gigantic electrical power output the results were still exactly the same. Well, at least there was a consistent pattern. Since they couldn't help I finally called Sherrill Marine and shazam! in less than 5 minutes after stepping on the boat they had solved the problem. (and collected 80 bucks - which I was more than happy to pay since that's ALL this problem would cost me to fix) It turns out that sea water had backed up from the exhaust thruhull all the way back into the engine, filling at least two cyclinders so that the engine couldn't spin rapidly enough to clear it. I NOW know there are pressure relief values on the top of my 3GM Yanmar engine that allows the engine to bypass the compression phase. With that values released, the engine quickly spun and ultimately started up just fine (and luckily without any damage fortunately). OK, so now, here's what the mechanic told me... and actually showed me: "the design of the water exhaust system does not provide enough of a rise in the elbow (really no elbow) to prevent sea water from backing up in rough sea conditions such as we experienced. The reason the exhaust thruhull is so very low is to create the maximum drop possible". BUT... again according to the mechanic, it's still not drop enough for the system to be trully sea worthy. The design issue is that the exhaust manifold runs under the aft berth (the key point I think) and then straight out to the thruhull at a small angle (rather than going up and then down). Two workarounds were offered but neither was a proper solution in the mechanics opinion. Basically the issue is inherent in the design of the boat. 1. install a seacock for manual shutoff when anchoring/mooring is rough conditions. Neither of us liked this idea for obvious reasons. (If the seacock wasn't reopened before starting the engine (from the cockpit of course) we could sink the boat before we even realized we had a problem.) 2. Put a temporary preventive obstruction in the outside of the thruhull when appropropriate. I think a tennis ball might work well here but frankly, I haven't tried this yet. (If forgotten the tennis ball would simply be blown away when the engine is started.) The only problem with this idea is that the tennis ball must be put in only during rough conditions and who wants to go overboard then? <s> Anyway, hope above is helpful. Please understand that I love my V32, but I sure would apprecriate a 3rd, and proper solution. Cheers Rodger
James, I learned the hard way that there is, according to a sharp mechanic at Sherrill Marine in Avalon, Catalina Island, CA, "a significant design issue with the raw water cooling systen on the V32". Here's the scoop, and a little "color": wife Dede and I were moored at Hamilton Cove, in Avalon's outer harbor beginning Friday morning, October 11. We were there for the weekend to a) celebrate Dede's birthday b) participate in our yacht club's cruise c) attend the Jazztrax an annual jazz concert. (We've been attending Jazztrax for past 9-10 years - it's a great event and the Avalon Ballroom where it is held is a stunningly beautiful venue.) Well, the weather was beautiful all weekend but the outer harbor was quite rough, with 2-4 foot swells coming almost accross the port beam. Sunday morning I decided to start the engine and charge up as the Harbor Master had just come by to say we could, at last, move inside. When I attempted to start the engine using just the house batteries and it would barely turn over. Strange, since I still had 12 volts+ on the meter. Then I engaged the dedicated starting battery and woe-of-woes, there was no improvement! This was indeed VERY strange (and I was thinking, probably very expensive also) as now meter be damned, I KNEW I had lots of juice. Because I'm not in the least mechanical, I then called Vessel Assist. But even with their gigantic electrical power output the results were still exactly the same. Well, at least there was a consistent pattern. Since they couldn't help I finally called Sherrill Marine and shazam! in less than 5 minutes after stepping on the boat they had solved the problem. (and collected 80 bucks - which I was more than happy to pay since that's ALL this problem would cost me to fix) It turns out that sea water had backed up from the exhaust thruhull all the way back into the engine, filling at least two cyclinders so that the engine couldn't spin rapidly enough to clear it. I NOW know there are pressure relief values on the top of my 3GM Yanmar engine that allows the engine to bypass the compression phase. With that values released, the engine quickly spun and ultimately started up just fine (and luckily without any damage fortunately). OK, so now, here's what the mechanic told me... and actually showed me: "the design of the water exhaust system does not provide enough of a rise in the elbow (really no elbow) to prevent sea water from backing up in rough sea conditions such as we experienced. The reason the exhaust thruhull is so very low is to create the maximum drop possible". BUT... again according to the mechanic, it's still not drop enough for the system to be trully sea worthy. The design issue is that the exhaust manifold runs under the aft berth (the key point I think) and then straight out to the thruhull at a small angle (rather than going up and then down). Two workarounds were offered but neither was a proper solution in the mechanics opinion. Basically the issue is inherent in the design of the boat. 1. install a seacock for manual shutoff when anchoring/mooring is rough conditions. Neither of us liked this idea for obvious reasons. (If the seacock wasn't reopened before starting the engine (from the cockpit of course) we could sink the boat before we even realized we had a problem.) 2. Put a temporary preventive obstruction in the outside of the thruhull when appropropriate. I think a tennis ball might work well here but frankly, I haven't tried this yet. (If forgotten the tennis ball would simply be blown away when the engine is started.) The only problem with this idea is that the tennis ball must be put in only during rough conditions and who wants to go overboard then? <s> Anyway, hope above is helpful. Please understand that I love my V32, but I sure would apprecriate a 3rd, and proper solution. Cheers Rodger
That's quite an experience Rodger!
My exhaust hose does a little half loop up pretty far in the aft locker before connecting to the thru-hull...I'm now guessing that's why... Thanks for the story! matt
My exhaust hose does a little half loop up pretty far in the aft locker before connecting to the thru-hull...I'm now guessing that's why... Thanks for the story! matt
My Big Mouth
Rodger is the owner of Attitude Adjustment, of which I was the prior owner. I never had anything like that happen, and was in some pretty rough stuff. However, Descanso Bay is where Rodger likely was and it is notorious for being sloppy. I thought the large (several foot)loop in the exhaust would prevent that backflow. It is exactly what I have now in my 40.5 and is the same as in a lot of modern boats I've seen. Can't argue with the experience, tho. One solution might be to increase the rise of the loop with new hose, I suppose. Worth a call to Hunter. Can't say I remember any such thing on these boards. Rick D.
Rodger is the owner of Attitude Adjustment, of which I was the prior owner. I never had anything like that happen, and was in some pretty rough stuff. However, Descanso Bay is where Rodger likely was and it is notorious for being sloppy. I thought the large (several foot)loop in the exhaust would prevent that backflow. It is exactly what I have now in my 40.5 and is the same as in a lot of modern boats I've seen. Can't argue with the experience, tho. One solution might be to increase the rise of the loop with new hose, I suppose. Worth a call to Hunter. Can't say I remember any such thing on these boards. Rick D.
Very interesting potential problem!
I'll have to look at my boat next time I'm down. I'm really curious about how tall the exhaust loop is in the aft compartment. One possible "band aid" might be some kind of a flap over the exhaust exit. I have not gotten down and actually looked to see if it's all feasable, but I'll keep it in mind....
I'll have to look at my boat next time I'm down. I'm really curious about how tall the exhaust loop is in the aft compartment. One possible "band aid" might be some kind of a flap over the exhaust exit. I have not gotten down and actually looked to see if it's all feasable, but I'll keep it in mind....
V-32 exhaust system
my 89 V32,"Quackers" has a loop in the exhaust hose in the starboard lazarette. If yours does not, why not install a bronze foot valve(like the one used in the bilgh pump hose to overboard) in the line somewhere between the muffler/mixer & the exit thru hull. They are made in many different sizes & are available in most plumbing supply stores. I don't know if there is a marine grade or not, but West Marine may have them Wayne
my 89 V32,"Quackers" has a loop in the exhaust hose in the starboard lazarette. If yours does not, why not install a bronze foot valve(like the one used in the bilgh pump hose to overboard) in the line somewhere between the muffler/mixer & the exit thru hull. They are made in many different sizes & are available in most plumbing supply stores. I don't know if there is a marine grade or not, but West Marine may have them Wayne
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