Dorade Vent Hoses for Cape Dory 25D

[Richmond]

Hi everyone,

I have two Dorade vents installed on the transom of my Cape Dory 25D, for the purpose of aerating the engine, but no hoses to connect to the vents. As a safety precaution, I've been leaving the engine cover off while motoring in order to make sure the engine gets enough air. But I'd like to install those hoses once and for all. The owners manual I have says that the vent deck plates are 3" (which I assume is the size that the hose should be), but the manual says nothing about the hoses. Does anyone know by any chance how long approximately the hoses should be in order to get enough air to the engine, as well as what kind of the material the hose should be (rubber, plastic, etc? When I went to west marine they said I should use the same kind of material that's used for the wet exhaust but that seems like overkill to me). Thanks everyone.

[Russell]

CD originally put in pretty flimsy wire reinforced ducting, not hose. Wet exhaust hose would definitely be serious overkill! And 3" wet exhaust hose will cost a fortune. My original ducting fell apart, yours probably did too and a previous owner just pitched it. I ran my boat without the ducting for years and never once worried about the engine getting enough air, the engine room is hardly airtight on my boat and I doubt it is on the 25D either.

If you look on the link below, two ducts listed, the top one is more or less what CD originally used on these boats (though I suspect what trident sells is actually better then what CD used). When I replaced mine I used the second one, the blue stuff, a bit sturdier and won't permanently deform because its reinforced with plastic rather then wire so it springs back to shape better.

http://www.tridentmarine.com/stage/ventduct.htm

As for lengths needed, I can't help there, but it shouldn't be hard to get a fair idea with some measuring tape and just buying a few extra feet to be sure.

[Steve Laume]

Your West Marine guy is an idiot. And I don't often say that about anyone.

On Raven I turn the port vent forward and the starboard one aft. The port side has a hose long enough to exit low and close to the alternator. This is where I want the most air to help with cooling the alternator. The starboard side has a short hose, mounted high, to take away hot air in the engine compartment. A few years ago I added an in line bilge blower to evacuate the hot air before the engine is shut down. It works great to cool the engine compartment and help keep the cabin cool. It is noisy and I need to remember to turn it on so it doesn't always get used and is probably unnecessary. When you do run your hoses, make sure you don't have any low spots that could hold water.

I had some dust collector hose that I use in my shop so that is what I used. It seems very similar to what Russel posted and is nice to work with. The white, stiff stuff gets kid of nasty after a while and is not as flexable but would certainly be serviceable, Steve.

[Joe Myerson]

I ran my boat without the ducting for years and never once worried about the engine getting enough air, the engine room is hardly airtight on my boat and I doubt it is on the 25D either.

Russell,
I've been sailing with the shoddy, cracked original ducting for years. It's time I removed it. I'm wondering if I should try to go without. It would certainly give more room to move around near the engine--nobody would call that cramped hole an "engine room."

--Joe

[Dick Kobayashi]

I don't think the hoses are that important, but the vents are. There will always be enough air for engine combustion, but not necessarily to ventilate the "engine room" so that the heat is dissipated to the atmosphere.

The solutions recommended seem fine - but if you forgot to do anything it would likely be fine too.

[Richmond]

Thanks everyone for the great tips. Thanks Steve especially for explaining how the hoses are set up on your boat. And yes lol I'll concur with your opinion on the West Marine person. Once I was quoted a price of $27 a foot to buy the hose, I politely excused myself and said I'd think about it... I think I'll try going without them and see how that works out, and then consider getting the blue trident hose you suggested Russell. Thanks again everyone.

While we're on the topic of engine compartments, I need to replace my throttle cables. Anyone know how long the cable is in the Cape Dory 25D so I can order it before I remove it to measure it?

[M. R. Bober]

CD originally put in pretty flimsy wire reinforced ducting, not hose. Wet exhaust hose would definitely be serious overkill! And 3" wet exhaust hose will cost a fortune. My original ducting fell apart, yours probably did too and a previous owner just pitched it. I ran my boat without the ducting for years and never once worried about the engine getting enough air, the engine room is hardly airtight on my boat and I doubt it is on the 25D either.

If you look on the link below, two ducts listed, the top one is more or less what CD originally used on these boats (though I suspect what trident sells is actually better then what CD used). When I replaced mine I used the second one, the blue stuff, a bit sturdier and won't permanently deform because its reinforced with plastic rather then wire so it springs back to shape better.

http://www.tridentmarine.com/stage/ventduct.htm

As for lengths needed, I can't help there, but it shouldn't be hard to get a fair idea with some measuring tape and just buying a few extra feet to be sure.

Russell,
The link/info re: Trident Marine vent hose is the most useful thing I've found in a long time. I have replaced those vent hose many times, on several CDs with both the original crappy vinyl and aluminum dryer vent hose (neither is much of a solution). Dick Kolwalski, on SANDPIPER replaced all of his vent hose with PVC pipe, and did a beautiful job. I will order the Trident hose on Monday.
Thank again for the link.

Mitchell Bober
Sunny Lancaster, (Where we don't rant; we vent.) VA

[frank3]

one thing to keep in mind on the 25d is the proximity of the starboard dorade to the back of the engine control panel. I 've always worried that water could get on the back of the conrol panel so I replaced mine with the wire reinforced flex hose, just in case.

[hilbert]

I wonder if the dorade vents on the transom aren't boat vestigiality, like the factory installed blower switch.

1) I seriously doubt the engine could create any vacuum in the space, with all the cracks and holes between the compartments.
2) Diesels are cooled by water, not air.
3) Here is a picture of a CD28 that circumnavigated the globe, in various climates without dorade vents.

[Sea Hunt Video]

I thought the air vents near the transom on my little CD 25D were primarily for providing air to the diesel air intake system. Am I wrong

[Steve Laume]

I thought the air vents near the transom on my little CD 25D were primarily for providing air to the diesel air intake system. Am I wrong

The engine will run just fine with whatever air gets in there.

The problem is excess heat. Raven has a larger alternator and it can get hot. I run the intake hose right down close to it. It doesn't do anything else in the engine compartment any good to be hot either. On the CD-30 the engine compartment shares a bulkhead with the ice box. I want to keep the area on the other side of the ice as cool as possible. The engine compartment is only separated from the cabin space by a little plywood and the galley sink. If you are sailing in cold climates you might enjoy the extra heat but most times not. These are the reasons I run the vent hoses and even installed a blower.

When motoring into a dead still anchorage on a sweltering hot day I run the blower when getting ready to anchor and leave it run for a little while after the engine is shut down. Cooling down the engine compartment helps a lot, Steve.

[Sea Hunt Video]

Steve:

OK, thanks. In addition to the vents I keep the engine compartment's hatch completely open. Up until today I would have said I did this so I could more easily hear any unusual noises, smells, etc. Now, I guess I have two reasons to keep the hatch off the engine compartment - sounds, smells, etc., and heat dissipation.

Thanks.

I plan to install new dorade vent hoses later this summer. I will get the ones recommended by Russell and others.

[hilbert]

Alternators are designed to run in hot engine compartments. I don't doubt that that they run more efficiently and with longer longevity at moderate temperatures (also true for batteries).
With a stock alternator (~35 amps) that is not the primary charging source, I don't worry much about it. One salt water soaking from a rouge wave is worse for the alternator than a boatload of hot summer days.

[Steve Laume]

Just to clarify the hose routing; the intake hose terminates at the port side of the engine near the alternator. It is not aimed directly at the device and there is no way for water to be directed onto it. The main idea of the hoses is to get the air circulating in the engine compartment and exhaust the hot air and associated smells.

I definitely wouldn't want to motor with the engine access panel opened. I have gone to some trouble to quiet the engine noise on Raven but can still hear when something is not right.

Not running a hose for the inlet is like the inverse of having the cold air return directly under your hot air outlet in a home heating system.

Running a vent hose is not really a big or expensive job. Unless you buy 3" exhaust hose to do it, Steve.

[Oswego John]

After reading the ads for vent hose, the one biggest thing that bugs me is that it comes in 50' lengths.

But then, again, I sail a Ty.

To quote my hero, Alfred E Neuman "What, me worry?"

O J