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-   -   Engine room insulation and positive feed air (https://www.cruisersforum.com/forums/f54/engine-room-insulation-and-positive-feed-air-237934.html)

islanderp40 03-08-2020 07:39

Engine room insulation and positive feed air
 
Howdy mariners all,

Currently, installing new insulation in the engine room using Sounddown 1'' thick heavy material.

Because of the weight I'm using the 3M 90 that I have tested and is very good strong adhesive.

As may be expected the 3M 90 is something not to be breathed in.

I have on order a 3M painters respirator.

In addition I want to install a 12v blower on the engine room air intake and have it running while I appy the adhesive which must be applied to both surfaces in place.

Close proximity is unavoidable.

I figured I could leave the blower in place when motoring and the positive airflow would be a benefit to the engine especially in hot weather.

Comments, suggestions welcomed.

steve77 03-08-2020 08:15

Re: Engine room insulation and positive feed air
 
Good thoughts on using a source of outside air while spraying the adhesive.

As far as using the blower to supply cool air to the engine, I know there have been posts on this topic before, but I can't remember when. From memory, the consensus was that there are enough air leakage paths to supply the engine with fresh air for combustion. If you want to cool the engine room, you are better off using the blower to remove heated air from the engine room. Of course, this may not be true for your boat, depending on how attentive to detail you are when you install the sound insulation and if any gaps remain.

With that being said, if you have a high output alternator you may want to use the blower to direct outside air to it to help keep the alternator cooler.

Just some thoughts...

By the way, we pulled out of Seabrook marina in 2015. I still wear my Blackburn T-shirts often, and am wearing one now. Cheers!

Steve

wingless 03-08-2020 17:54

Re: Engine room insulation and positive feed air
 
When I moved my New England boat to the tropics, it transitioned from never having heat soak vapor lock, to always having vapor lock after stopping for an hour.

My solution was to install a pair of high volume, thermostatically controlled heat exhaust blowers, sucking from up high, above each engine.

This solution has been 100% effective at the elimination of the heat soak vapor lock problem.

Warby12 03-08-2020 18:10

Re: Engine room insulation and positive feed air
 
I have often thought of adding positive venting into the engine compartment. Like steve77 says, if you have it, handy to direct it at the alternator, (not if any chance of salt spray though haha). The thing that has stopped me is that if the engine compartment is at higher pressure than the cabin, would we get engine smells into the cabin? Don't know but it always stops me.

ggray 03-08-2020 18:37

Re: Engine room insulation and positive feed air
 
Quote:

Originally Posted by Warby12 (Post 3201060)
I have often thought of adding positive venting into the engine compartment. Like steve77 says, if you have it, handy to direct it at the alternator, (not if any chance of salt spray though haha). The thing that has stopped me is that if the engine compartment is at higher pressure than the cabin, would we get engine smells into the cabin? Don't know but it always stops me.

Yes, that is the problem.

boatpoker 03-08-2020 20:20

Re: Engine room insulation and positive feed air
 
Quote:

Originally Posted by Warby12 (Post 3201060)
I have often thought of adding positive venting into the engine compartment. Like steve77 says, if you have it, handy to direct it at the alternator, (not if any chance of salt spray though haha). The thing that has stopped me is that if the engine compartment is at higher pressure than the cabin, would we get engine smells into the cabin? Don't know but it always stops me.

Two blowers ... intake from one side, output to the other.
Pretty much like venting a gasoline engine compartment.

Safe Ventilation of Gasoline Engine Compartments

Valmika 04-08-2020 12:34

Re: Engine room insulation and positive feed air
 
Quote:

Originally Posted by ggray (Post 3201073)
Yes, that is the problem.

My Engine room like most has an exhaust powered fan and an intake 4 inch hose from the outside. That way your engine room is at a lower pressure then the cabin since you are sucking the hot air out.

Scubaseas 04-08-2020 12:34

Re: Engine room insulation and positive feed air
 
I have a 4" high CFM tubaxial exhaust fan ducted from the top of the alternator to a dorade and a make up air from a separate dorade to the opposite side of alternator side of the engine lower down. The amount of heat that comes out on the exhaust fan is impressive and it makes a huge difference on how much electricity I use for the fridge.

CarinaPDX 04-08-2020 13:32

Re: Engine room insulation and positive feed air
 
Run the fan for exhaust, not intake. You do not want positive pressure. Also, be certain that it is ignition-protected; you don't want sparks flying from the brushes with the solvent vapor in the air (from the adhesive). My Volvo's installation manual calls for an exhaust fan, and provides guidance for the flow rate - it is a good idea for all engines. Most "marine" exhaust fans are made for clearing the engine compartment for 5 minutes before starting a gasoline engine, and will not last long in continuous use. A good, continuous duty fan can be bought from Delta-T.

Greg

Scubaseas 04-08-2020 13:43

Re: Engine room insulation and positive feed air
 
I put in a 4" Shurflo "yellowtail" (what it's now called) and it runs anytime the motor is on. It's still good after 12 years/800 hours.

Mike Banks 04-08-2020 15:14

Re: Engine room insulation and positive feed air
 
I used to have a motor vehicle brush-less radiator fan that could be switched on when the engine is running. It shifted a LOT of air and quickly. I used it to push air into the engine room, and it exited via 2 stainless steel deck-stepped ventilation shafts that doubled as supports for the cabin roof.

Smaller fans would probably have worked, it is just that this fan was better and cheaply obtained from a wrecker of motor vehicles.

Cheechako 04-08-2020 15:35

Re: Engine room insulation and positive feed air
 
Your boat doesn't already have an engine room blower?
I often ran the blower continuously to keep heat out of the boat in the Caribe, or summer.

Valmika 04-08-2020 15:54

Re: Engine room insulation and positive feed air
 
[QUOTE=islanderp40;3200533]Howdy mariners all,

Currently, installing new insulation in the engine room using Sounddown 1'' thick heavy material.





Let us know how the insulation worked out over the stock stuff. I was thinking of changing mine out too.

Bycrick 04-08-2020 16:13

Re: Engine room insulation and positive feed air
 
If you’re installing the foam with an adhesive, I would also use some screws. I did exactly this project using adhesive. About 10 years later, the foam itself started to give way. Whole sections would decide to fall off the bulkhead. That would have been bad enough. Worse was that the adhesive and a thin layer of dead foam stayed firmly and solidly on all of the surfaces. Getting THAT off to replace the foam was by far the worst part of the job.

David B 04-08-2020 22:19

Re: Engine room insulation and positive feed air
 
Quote:

Originally Posted by islanderp40 (Post 3200533)
Howdy mariners all,

Currently, installing new insulation in the engine room using Sounddown 1'' thick heavy material.

Because of the weight I'm using the 3M 90 that I have tested and is very good strong adhesive.

As may be expected the 3M 90 is something not to be breathed in.

I have on order a 3M painters respirator.

In addition I want to install a 12v blower on the engine room air intake and have it running while I appy the adhesive which must be applied to both surfaces in place.

Close proximity is unavoidable.

I figured I could leave the blower in place when motoring and the positive airflow would be a benefit to the engine especially in hot weather.

Comments, suggestions welcomed.

You have negative pressure in the engine bay - otherwise you end up with engine fumes in the cabin.

If you did nothing, the pressure would be negative just from the engine breathing, but that is not good practice. You need at least an air inlet duct (or two) to supply the engine air and aid ventilation.
Then ideally, a blower taking air out of there (one duct out, two ducts in gives reasonable balance allowing for the engine as well. That is typically the way many modern boats are set up.
This gives significant airflow through the engine bay for engine aspiration, cooling and ventilation, while still maintaining a slight negative pressure to ensure the fumes go overboard, and not into the cabin.


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