Blower Ducting - Maxum Boat Owners Club

viper12161 · 03-10-2016, 08:08 PM

Hey everyone,

So I just got a 2004 1800 SR3. I am going through it to make sure all is well and I found one of the blower vent hoses is torn. The thing that is throwing me off, is there are 2 hoses in there. One connects to the top of a white fixture that says "Atwood Turbo 4000" on it. I'm assuming this is the suck and it exits out of the boat. There is nothing on the bottom of this fixture (see pic) but I read there should be another short hose piece that goes down further into the bilge. Easy fix. The second hose (which is the torn one) goes up and connects to a vent on the top of the boat but the bottom half is just hanging in the engine compartment. (See other pic). I'm thinking this is fresh air in or something for when the boat is under way...but I find it weird that it's just hanging there. Any advice would be great!! Not blowing up is a big concern of mine, so I want to make sure this is right. Thanks!!

Dave

mmwjr · 03-10-2016, 10:35 PM

Welcome aboard

You got it the one hose is a fresh air intake and should be about where it is in the picture. It is typically secured at its end but may have several inches hanging free from where it is secured.

The intake to the blower should go to the very bottom of the bilge.

Procedure is to run the blower for four minutes before starting the engine.

viper12161 · 03-10-2016, 10:54 PM

Thanks for the info! So really all that is needed is to add that short piece of hose to the bottom of the intake and let run down into the bottom of the bilge. Is there any particular type of special hose needed for that bottom piece, or just another section that is the same as the uppers.

mmwjr · 03-11-2016, 03:08 AM

Standard 4" blower hose same as the rest. Can be found at your local boat supply store such as West Marine.

Zathrus · 04-05-2023, 11:33 PM

How are the 2 hoses connected to the side vent? I can't find any pictures or diagrams on this topic anywhere and can't get up in there to see what's going on.

If they are both connected to the same vent won't the fresh air intake just suck the fumes right back into the bilge? It would seem logical to me that one side vent should be connected to the fresh air intake hose and the opposite side be connected to the exhaust hose, but there is no hose even connected to the starboard side vent on my boat (1800 SR3) and because the exhaust vent is way up high on the port side of the boat, the gas fumes quite often just waft into the cabin area. Seems like an idiotic design to me.

I would have both side vents pull in fresh air and a separate exhaust vent exit out the stern somewhere and direct the fumes away from the cabin. I would also like to see some sort of ventilation down under the floor area too as anything I put down in my ski locker between the seats smells of gas fumes too.

As far as turning the blower off once underway. This sounds ok if you're only talking about gas fumes but what about fresh air for the engine and on a scorching hot summer day it's bound to get pretty smokin' hot in the engine bay too so it couldn't hurt to vent some of that heat as well. It's not like the blower draws a ton of current.

Am I alone on all of this?

mmwjr · 04-06-2023, 08:04 PM

Typically the intake is one side and the exhaust is the other. But some exhaust out the stern however this has been stopped due to the station wagon effect where exhaust air can get sucked into the aft by turbulence. The hose is attached with a zip tie.

Zathrus · 04-06-2023, 08:18 PM

Still curios if anyone knows if both exhaust and intake hoses are connected to the same vent on the port side. I can't tell.

mmwjr · 04-07-2023, 07:21 PM

Not familiar with your model so I cannot help.

shrew · 04-12-2023, 04:09 PM

You would usually have the intake in a separate area from the discharge. Some dorade boxes have the intake facing forward and the discharge facing aft with the sections of the Dorade box isolated from one another.

some intake from one side and discharge from the other. I suggest configuring in a manner that doesn't inadvertently draw from the discharge into the intake.

viper12161 · 04-12-2023, 05:25 PM

Quote:

Originally Posted by Zathrus

How are the 2 hoses connected to the side vent? I can't find any pictures or diagrams on this topic anywhere and can't get up in there to see what's going on.

If they are both connected to the same vent won't the fresh air intake just suck the fumes right back into the bilge? It would seem logical to me that one side vent should be connected to the fresh air intake hose and the opposite side be connected to the exhaust hose, but there is no hose even connected to the starboard side vent on my boat (1800 SR3) and because the exhaust vent is way up high on the port side of the boat, the gas fumes quite often just waft into the cabin area. Seems like an idiotic design to me.

I would have both side vents pull in fresh air and a separate exhaust vent exit out the stern somewhere and direct the fumes away from the cabin. I would also like to see some sort of ventilation down under the floor area too as anything I put down in my ski locker between the seats smells of gas fumes too.

As far as turning the blower off once underway. This sounds ok if you're only talking about gas fumes but what about fresh air for the engine and on a scorching hot summer day it's bound to get pretty smokin' hot in the engine bay too so it couldn't hurt to vent some of that heat as well. It's not like the blower draws a ton of current.

Am I alone on all of this?

So my fresh air in vents are on the sides of the boat and the exhaust exits through a vent in the back of the boat. Reason blower is not required while under way is the speed of the boat pushes fresh air into those vents and provides ventilation that way. Kinda like having the windows down

Zathrus · 04-12-2023, 10:13 PM

Thanks for the reply guys but my original question still remains unanswered.

"I'm curios if anyone knows if both exhaust and intake hoses are connected to the same vent on the port side. I can't tell."

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~

2005 Maxum 1800 SR3

viper12161 · 04-12-2023, 10:21 PM

No...my intakes are on the side, my exhaust is on the back.

Zathrus · 04-12-2023, 10:26 PM

I have no vents on the back of my 2005 1800 SR3 so where does the exhaust exit the boat?

viper12161 · 04-12-2023, 10:35 PM

More than likely the side. I have a cabin cruiser, so a bit different than the SR3. I sold my SR3 a while ago and trying to remember how the bilge ducting went, I think, and big think here....the fresh air intake comes in on the port side. That's the one that provides air while under way. There is another one there that connects to the input of the blower. And then the exhaust goes out the bottom of the blower to the starboard side. I do remember it being tight and a huge PITA to work on. There's a separate forum section for sport boats...maybe pop your question there. Might get folks a bit more familiar with that hull, but sure.

mmwjr · 04-13-2023, 12:46 AM

From what I know one side should be intake and the other side exhaust. Although I have seen the forward of both sides be intake and the aft exhaust.

Can you post some pictures of the vents?

Zathrus · 06-29-2023, 12:12 AM

I'm finally getting to the bottom of this blower venting conundrum.

My starboard side vent had nothing attached to it inside the boat. Just 2 - 4" holes drilled into the vent box at the rear. The port side has the same 2 - 4" holes. 1 was connected to the blower hose and 1 connected to the intake hose. so outgoing gas vapors end up getting recirculated back into the engine compartment. Not to mention the fact that the vent box is not sealed properly and when the blower is on it leaks fuel vapors out everywhere in the gunwale area underneath the vent box thus into the cabin. This is unacceptable to me and a retarded design IMO

So, I replaced the flexible dryer style hose with some no-ribbed flexible aluminum ducting and ran it from the starboard vent down into the bottom of the bilge along with the blower motor and plugged up the other 4" hole and siliconed any leaks in the vent box. I then ran another hose from the port vent and fed it up near the top of the engine for fresh air inlet. In retrospect it should probably be the other way around venting out the port side but that puts the output hose near the batteries where sparks could happen and I liked the idea of being able to smell any gas vapors on the starboard side near my helm before I turn the key.

FYI: Dryer vent hose has big ribs in it that cause turbulence and decrease air flow by 4 to 1 over straight pipe. The aluminum flex hose has very tiny ribs in it which result in dramatically increased airflow and longer blower motor life.

The only down side to all of this is that the aluminum hose echoes and increases blower motor noise but I can live with that for now. At least I know I'm now getting excellent ventilation. I plan to wrap the hose with something to dampen the noise later along with some engine compartment insulation matting to quiet the engine noise as well.