Quick question on venting my Merc

[jasoutside]

OK guys, I am running the ventilation system for my Merc 4.3 and have a question for ya.

First, here's my setup:

I have two scoops at midships for fresh air intake. One of those I'll be adding an inline blower.

Then I have two scoops at the stern for exhaust. Both of those will have in line blowers.

I'm using this stuff for the ducting...

It's great, heavy duty, flexible stuff!

Now, here's my question:

Can I run the hose/blowers to here, right at deck level, with the blower kinda pointing in towards the bilge?

Or is that entirely unacceptable? Must I get em down into the bilge under the engine?

Here's why I ask...

Running the hose under the Merc kinda mid engine is fine but man does it block everything up! See...

One more thing getting in my way of draining the block and swapping that oil filter.

Over on the starboard side, I have just barely enough room to sneak that hose down in there. I have to sort of smush it in there, super tight.

Another option is to run that hose along the sides of the engine then down into the bilge at the front side of the Merc, kinda like this...

I do have a beef with going that route though: I'll need to build my doghouse a few inches wider to accommodate the hose. Space back there is at a real premium, it's getting pretty tight for access at the stern and my jump seats.

Anyway, help me out guys, must the vent hose be under the engine or is that deck level placement acceptable?

 

[Teamster]

Re: Quick question on venting my Merc

Is there any reason with it mid-engine that it couldn't be pulled out to drain, change oil filter etc?????

 

[jasoutside]

Re: Quick question on venting my Merc

Is there any reason with it mid-engine that it couldn't be pulled out to drain, change oil filter etc?????

Great question!

If I have to run those hoses under the engine into the bilge (at mid engine) I was planning to actually mount the blowers so they don't flop around. I suppose making the port side removable could be possible.

For the starboard side, it's not even an option. That hose will be stuffed in and that's it.

 

[achris]

Re: Quick question on venting my Merc

Hi Jas,
I have also a blower hose in my bilge. I've it running down the transom and into the bottom of the boat (it needs to be as near to the bottom as possible, petrol fumes sink) passed the back of the exhaust Y-pipe, and down...

I'll dive out and get some photos tomorrow for you...

Chris.......

 

[maddiedog]

Re: Quick question on venting my Merc

Jason,

My blower motor is mounted up on the transom with the hose going on both sides. The other end is pushed down behind the engine into the bilge.

 

[jasoutside]

Re: Quick question on venting my Merc

Hey guys, thanks!

I'll say, I can't really fit the hose "between" my Y Pipe and the transom. The best I got with that kinda route is that last photo I posted there with the hose just to the outside of the Y Pipe.

I could potentially run the hose between the Y pipe and the engine block itself (if that makes sense) on the port side. Can't do that on the starboard side though.

 

[JASinIL2006]

Re: Quick question on venting my Merc

When I was routing my hoses, I was trying to figure out to get the blower hose intake into the bilge, too. I was trying to find something like a vacuum cleaner nozzle for a ShopVac that I could mount along side the bilge to which I could attach the hose. I never found anything that was quite the right size, so I ended up just flattening the hose a bit (I used a plastic hose with spiral-wire insert, so it held the shape) and fastening the flattened end to the bilge wall. I couldn't have located the intake close enough to the bilge if I had attached the blower to the lower end of the hose. There just isn't enough room. The blowers are designed to operate in-line, so mounting the blower on the inside of the transom got it out of the way.

Good luck and if you come up with some ingenious solution, I'd be interested to see it!

Jim

 

[Grandad]

Re: Quick question on venting my Merc

Hi Jas, I wouldn't put the hose end much below deck level. I'd stay well above any possible bilge water level that could block the air flow. I know, your bilge will always be dry, but when starting the engine after a sudden downpour, you don't need any obstruction to airflow. Yes, fumes may be heavy, but they're not made of lead and any significant air movement will draw the fumes up a few inches. Also, remember that you're worried about fumes being ignited by a component that's not in the bottom of the bilge anyway. Smushing the end of the hose is a good way to keep it in place at the right level. Also, if you mount the blowers a foot or so above the deck on the transom, they won't be as likely to get wet and there'll be more flexibility on the bilge side hose for smushing and unsmushing for easy access while doing maintenance. _ Grandad

 

[Bondo]

Re: Quick question on venting my Merc

OK guys, I am running the ventilation system for my Merc 4.3 and have a question for ya.

First, here's my setup:

I have two scoops at midships for fresh air intake. One of those I'll be adding an inline blower.

Then I have two scoops at the stern for exhaust. Both of those will have in line blowers.

I'm using this stuff for the ducting...

Ayuh,.... Just curious,.... Why so many Blowers,..??

1(one) suckin' outa a line from as deep as possible/ practical in the bilge, blowin' out the back, is Plenty,....

Yer hull with it's clams shells self vents pretty good in the wind, much less at speeds,....

Gas is heavier than air, so 1 line from down deeper to the blower, 'n the other out line can be from where ever ya want,...

 

[jasoutside]

Re: Quick question on venting my Merc

Hey, thanks for chipping in fellas, I think I have it sorted.

Bruce, yah, I know I have more than I need. Basically, I had 4 giant holes in my gunwales and stern deck. So, 4 scoops to fill those. Might as well hook up some hoses for venting while I'm at it.

I also have 3 blowers, 2 new ones I scored cheap off eBay and one left over from a dead glasser. So, I figured I may as well use em.

My doghouse won't be tight to the transom. I'll actually have tons of ventilation available even without the blowers, so, way overkill all in all.

Anyhow, here's what imagonnado....

For the port side, I'll mount the blower on the transom (blue) and have the vent hose (green) run loose down into the bilge under the engine to exhaust any fumes up and out. Like yo...

That way I can just pull the hose up and out of the way when it comes time to drain the block and change the oil filter. Good stuff.

For the starboard side I'll mount the blower so it's shooting fresh air into bilge. Basically like this, just reversed for the starboard side...

So, that setup ^^^^, I can keep my doghouse as small as possible and still have good access to wrench on the Merc. I think that's a pretty good compromise eh:thumb:

Cheers fellas!

 

[JASinIL2006]

Re: Quick question on venting my Merc

Why do you need to shoot air INTO the bilge? I don't understand....

Also, maybe your engine enclosure is more soundproof than mine, but when I'm running at low speeds, the blower noise is noticeable. It's not too loud to talk over, but until I'm at cruising RPMs, you can hear blower. I wouldn't want two of those running on my boat all the time.

 

[jasoutside]

Re: Quick question on venting my Merc

Why do you need to shoot air INTO the bilge? I don't understand.....

Yup, I don't think I "need" to either. It'll just bring more fresh air in is all. I could just as easily turn it the other way and have two blowers exhaust. Heck, I could omit that one all together really.

 

[Bondo]

Re: Quick question on venting my Merc

Yup, I don't think I "need" to either. It'll just bring more fresh air in is all. I could just as easily turn it the other way and have two blowers exhaust. Heck, I could omit that one all together really.

Ayuh,.... Mount the blowers, High, as high as possible, 'n put the hoses low,...

 

[jasoutside]

Re: Quick question on venting my Merc

Ayuh,.... Mount the blowers, High, as high as possible, 'n put the hoses low,...

Easy enough, I have plenty of flexibility with that.