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Old 15-07-2015, 12:01   #1
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Adding engine room vent

Our boat does not have an engine room vent, and I want to add one.

Does anybody have any tips? I plan on exhausting out high on the port side at the same level as the fuel and waste tank vents.

Do I need some kind of dorade? or way to close it? What's the best fitting for outside the boat?

Anyhow, just thought I'd ask if anybody had any tips to share.
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Old 15-07-2015, 12:22   #2
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Re: Adding engine room vent

the clamshell ss vents that have 3" or 4" ventilation hose fittings worked good on my boat if you have a vertical surface.
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Old 15-07-2015, 12:29   #3
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Re: Adding engine room vent

Clamshell vent cover, usually a loop inside in the hose is good choice also. Often there is another air inlet vent allowing cool air in while the fan takes out the warm air. They should be separated.
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Old 15-07-2015, 13:30   #4
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Re: Adding engine room vent

You want to make a 4" hole on the outside of your hull!!!!!! Something I wouldn't consider doing ever unless absolutely needed. If you do drill that big a puka, would want to have a way to make it water tight. Would try and find a way on deck or in the cockpit to exit the exhaust where it is not so apt to be under water.

A vent is probably nice but have owned two boats without any vents other than the gaps that allow air to get in and out the engine room. Both haven't had a problem with engine operation though may add some heat in the cabin though haven't noticed it.
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Old 15-07-2015, 15:22   #5
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Re: Adding engine room vent

I too am adding a powered vent. I already have two clamshells but I plan on installing a 4 inch bilge pump fan on the tube of one of them. We will keep the vent on a breaker so we can turn it on and off manually - we want to be able to run the vent for a while after the engine is stopped or when we are working in the locker.
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Old 15-07-2015, 16:24   #6
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Re: Adding engine room vent

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Originally Posted by zboss View Post
I too am adding a powered vent. I already have two clamshells but I plan on installing a 4 inch bilge pump fan on the tube of one of them. We will keep the vent on a breaker so we can turn it on and off manually - we want to be able to run the vent for a while after the engine is stopped or when we are working in the locker.
Yeah, good idea, it takes a while to get the heat down in the engine room in the tropics. If a berth is right next to it , it heats that berth a lot. You don't really need a vent on a diesel except to get the hot out.
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Old 15-07-2015, 17:09   #7
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Re: Adding engine room vent

Just a thought, here, guys, if you ever have a knockdown to the side you put your vent, you have a vent-sized water inlet direct to the engine and all its connections. Not sure I'd want that.

If the engine is not currently overheating, you only want the vent for cooling you while you're working on it. An exterior fan that can be aimed at you will do that, with less potential risk.

Just my two cents' worth.

Ann

PS to roverhi: how many people outside HI know what a kipuka is?
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Old 15-07-2015, 17:34   #8
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Re: Adding engine room vent

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Originally Posted by Ann T. Cate View Post
Just a thought, here, guys, if you ever have a knockdown to the side you put your vent, you have a vent-sized water inlet direct to the engine and all its connections. Not sure I'd want that.

If the engine is not currently overheating, you only want the vent for cooling you while you're working on it. An exterior fan that can be aimed at you will do that, with less potential risk.

Just my two cents' worth.

Ann

PS to roverhi: how many people outside HI know what a kipuka is?
Obviously, that is a legit concern. However, on our vessel was built with the clamshells are on the rear of the cockpit coaming far from the engine or anything electrical besides our waterproof SSB tuner. If the power fan gets wet... so what... it's $40. So far, we have never gotten a drop of water through the clamshells, even when cleaning the decks and spraying directly beneath the vent with the hose.
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Old 15-07-2015, 17:34   #9
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Re: Adding engine room vent

Quote:
Originally Posted by Ann T. Cate View Post
Just a thought, here, guys, if you ever have a knockdown to the side you put your vent, you have a vent-sized water inlet direct to the engine and all its connections. Not sure I'd want that.

If the engine is not currently overheating, you only want the vent for cooling you while you're working on it. An exterior fan that can be aimed at you will do that, with less potential risk.


Ann's right. We have two vents, in & out with a blower. Never use it. If you want to get cooler, run a big fan over you.

As an HVAC engineer, a 4 inch duct with small or even HUGE blower simply isn't gonna move enough air to do much good.

Those blowers were installed on soooo many boats. Why? 'Cuz they came with engine cockpit control panels which were originally made in the 1970's for GAS engined boats!!! Useless as t's on a bull for a diesel.

If you have smells, get rid of 'em.

If you have heat, well it's a big engine that makes heat. It dissipates rather quickly once the engine is off. If it's too hot down below when motoring then a 4 inch blower ain't gonna cut it.

Good luck.
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Old 15-07-2015, 18:30   #10
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Re: Adding engine room vent

I've got two. The air intake fan sucks from a cool cockpit locker with vent holes and blows its output directly on the alternator to keep it happy. The air exhaust vent pulls it from the highest point in the engine room and vents it out through a dorade box through the underwing. This is a pic of the exhaust fan, upper left corner with the blue fan.
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Old 15-07-2015, 18:34   #11
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Re: Adding engine room vent

I found having a blower to make huge difference in heat when motoring a long ways. Like 8 hours overnight.
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Old 15-07-2015, 19:23   #12
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Re: Adding engine room vent

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Originally Posted by Cheechako View Post
I found having a blower to make huge difference in heat when motoring a long ways. Like 8 hours overnight.
Two comments here: to Cheechako, I'm surprised by that, especially as the air is pretty cool in your cruising grounds. We've only had overheating problems when the cooling passages in the engine were getting clogged, but both engines involved already had good air supplies.

To Zzboss,

I certainly wouldn't expect you to change your arrangement under the circumstances. If you turn turtle, scramble back there and jam the biggest possible towel in it, and it will slow the water coming in.

Ann
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Old 15-07-2015, 20:24   #13
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Re: Adding engine room vent

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Originally Posted by Ann T. Cate View Post
Two comments here: to Cheechako, I'm surprised by that, especially as the air is pretty cool in your cruising grounds. We've only had overheating problems when the cooling passages in the engine were getting clogged, but both engines involved already had good air supplies.

To Zzboss,

I certainly wouldn't expect you to change your arrangement under the circumstances. If you turn turtle, scramble back there and jam the biggest possible towel in it, and it will slow the water coming in.

Ann
Wasn't here, (Mexico and Carribean- 4 different boats) but it applied to my boats here to a less extent. I had no oengine overheating problems and wouldn't expect that without a fan. Just cabin heating and especially aft berths. Frankly I've not had an inboard boat without the engine room fan. The engine room walls radiate the heat for hours. Heat is often a plus up here in the PNW however.!
Anyone who puts the exit where it wil be an issue in an extended knockdown shouldn't be working on their own boat probably! Properly installed... in that situation you are likely taking a lot more water in elsewhere... like the companionway, portlite?, cockpit lockers....!
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Old 15-07-2015, 21:11   #14
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Re: Adding engine room vent

Some very good answers with opinions and reasoning.

Now it's:

Your boat, your choice time.
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Old 15-07-2015, 21:37   #15
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Re: Adding engine room vent

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Originally Posted by Cheechako View Post
Wasn't here, (Mexico and Carribean- 4 different boats) but it applied to my boats here to a less extent. I had no oengine overheating problems and wouldn't expect that without a fan. Just cabin heating and especially aft berths. Frankly I've not had an inboard boat without the engine room fan. The engine room walls radiate the heat for hours. Heat is often a plus up here in the PNW however.!
Anyone who puts the exit where it wil be an issue in an extended knockdown shouldn't be working on their own boat probably! Properly installed... in that situation you are likely taking a lot more water in elsewhere... like the companionway, portlite?, cockpit lockers....!
I agree.

We sleep in the aft berth on passages and the bulkhead is right up against the engine. It makes sleeping there very hot. The engine room stays hot for at least 3 hours and if I want to cool it faster I have to open the locker in the cockpit to let it vent or it just radiates that heat into the the cabin.

Also, this is where our fridge compressor is located. The idea was to blow ambient outdoor air over the compressor but I may just skip that and just pull air out of the engine room like I previously described.
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