Blower or no blower?

[sbw1]

One of my pet peeves is fuel dockhands who start to untie your boat before you have had a chance to perform a safety check for fumes and run the blowers. In a similar vein, dock hands who do not know how to securely tie a boat up when you pull in for fuel. This seems to be the rule around here rather than the exception. Everybody seems to be in a hurry. By way of contrast, Jacobson Marina in Frankfort has perhaps the best staff on the west coast of Michigan. Leland Harbor is pretty good too. Others, not so much.

 

[Ike]

make up your mooring lines with a big eye or loop on one end, big enough to easily drop over a bollard or a cleat. Keep the bitter end on your boat. Hand them the loop and instruct them to drop it over the bollard or cleat then you tighten it to where you want it and fasten it to a cleat on your boat. My wife who is new to boating was having real difficulties tying off lines so I did this and now she has no problem. Just drop it over the cleat, haul on the line nd tie it off yourself.

And don't ever allow a marina dock hand or a guest on your boat to fuel your boat. Do it yourself so it goes into the fuel fill, not the water tank or a pole socket and into bilge. I investigated far too many boat fires where a dock hand or a guest on the boat put the nozzle in the wrong socket.

 

[mobocracy]

On my 380 the manual says to only run them before starting the engines or when moving at idle. No idea how it gets better ventilation when underway. Good points.

The engine uses air for combustion, so at some tipping point in engine RPMs, you're drawing in more air than the blower due to the engine's air consumption for combustion.

My math may be wrong, but for my twin 350s, 1250 RPMs is just over 250 cubic feet per minute of air flow. I would think definitely at planing speeds you're greatly exceeding the blowers. There may be some argument that in the middle ranges even if the engine exceeds blower CFM air movement, the blowers are ventilating areas that wouldn't see very much air exchange due to air flow mostly happening at the upper part of the engine compartment.

I just run mine all the time, mostly because we spend a lot of time at hull speed and if they crap out, so be it, and I replace them with continuous duty blowers.

 

[skolbe]

View attachment 96031
One of my pet peeves is fuel dockhands who start to untie your boat before you have had a chance to perform a safety check for fumes and run the blowers. In a similar vein, dock hands who do not know how to securely tie a boat up when you pull in for fuel. This seems to be the rule around here rather than the exception. Everybody seems to be in a hurry. By way of contrast, Jacobson Marina in Frankfort has perhaps the best staff on the west coast of Michigan. Leland Harbor is pretty good too. Others, not so much.

I agree they tend to try and rush folks off the fuel dock. I tend to leave my wallet down below and once done fueling. Turn on the blower get my wallet and do a quick sniff test... At that point by the time the gas is paid for it is about 4 minutes or more.

 

[Henry Boyd]

The engine uses air for combustion, so at some tipping point in engine RPMs, you're drawing in more air than the blower due to the engine's air consumption for combustion.

My math may be wrong, but for my twin 350s, 1250 RPMs is just over 250 cubic feet per minute of air flow. I would think definitely at planing speeds you're greatly exceeding the blowers. There may be some argument that in the middle ranges even if the engine exceeds blower CFM air movement, the blowers are ventilating areas that wouldn't see very much air exchange due to air flow mostly happening at the upper part of the engine compartment.

I just run mine all the time, mostly because we spend a lot of time at hull speed and if they crap out, so be it, and I replace them with continuous duty blowers.

That's for a single engine (I got 506 total) at idle. At running speeds the blowers might even be impeding the air flow because when off, the impellers freewheel in reverse, but when on the impeller is at a fixed rpm in exhaust. I'm also not so sure a squirrel cage is a good idea as it may actually become a blockage when off.

 

[sbw1]

[QUOTE="Ike, post: 1185284, member: 24735"
And don't ever allow a marina dock hand or a guest on your boat to fuel your boat. Do it yourself so it goes into the fuel fill, not the water tank or a pole socket and into bilge. I investigated far too many boat fires where a dock hand or a guest on the boat put the nozzle in the wrong socket.[/QUOTE]

Rules may have changed, but when i refuel win Gore Bay in the North Channel, there is a requirement that all passengers must be off the boat, and dock attendants refuel the boat. A Canada thing, or a North Channel thing? I believe Little Current is the same but could be wrong about that.

 

[mobocracy]

That's for a single engine (I got 506 total) at idle. At running speeds the blowers might even be impeding the air flow because when off, the impellers freewheel in reverse, but when on the impeller is at a fixed rpm in exhaust. I'm also not so sure a squirrel cage is a good idea as it may actually become a blockage when off.

My math is 2 x 350 cubic inches = .405 cubic feet. 1 air intake for every 2 RPM.

.405 cubic feet * (rpm / 2) yields me 253 cfm @ 1250 rpm. I'm not sure the blowers being off would be a big airflow, I think there's enough passive air venting into the engine compartment at least on my boat for it not to matter.

 

[Henry Boyd]

My math is 2 x 350 cubic inches = .405 cubic feet. 1 air intake for every 2 RPM.

.405 cubic feet * (rpm / 2) yields me 253 cfm @ 1250 rpm. I'm not sure the blowers being off would be a big airflow, I think there's enough passive air venting into the engine compartment at least on my boat for it not to matter.

You’re right, I didn’t account for the exhaust stroke. Still the specs on a 4” inline blower is on the order of 100 to 125 cfm, so at idle/no wake speed engines are consuming around 2x the exhaust rate. I’m not so sure about your assumption of passive ventilation. We know there is no air movement between engine compartment and cabin because of CO and gasoline vapor concerns & protections. Engine hatches are gasketed, and the compartment is water tight.

WOT on the 350 is what about 4300 rpm? That would put maximum cruise at 3600ish, making top end engine air consumption at 750 to 800 cfm. At that level the entire air volume may be changing every minute.

As a point of reference an empty 20’ ISO shipping container has an internal volume of 1172 cubic feet (or air change at less than two minutes). With the hatch down I don’t think even the largest Sea Rays have that much air space in their engine compartments.

So once above idle speed running the blower is counter productive; the engine is going to consume far more hot air than a blower (or even two) is going to expel, that is even if the blower is powerful enough to work against the suction created by the engines.

 

[Greg Lions]

Perhaps even better would be for a cool air duct directed towards the engine intakes so the air they draw in is cooler...but probably just over engineering things....its damn too crowded down there as is!

 

[Lazy Daze]

Perhaps even better would be for a cool air duct directed towards the engine intakes so the air they draw in is cooler...but probably just over engineering things....its damn too crowded down there as is!

I may have mentioned this above, not sure, didn't bother re-reading. Yes, don't overthink this one - other than "for fun", of course! The system is already designed to fully meet the demands of the engine. Boat engines operate perfectly well as-is - they don't overheat due to air. Overheating is typically due to lack of water when there's an issue/problem with the cooling water system. Any "improvements" to the intake air system will not result in any measurable gains, if at all.

Also, most (all?) boats have a secondary air exit, separate from the blower exhaust port.

Remember, it's not about what we, as humans, "feel".

 

[northern]

View attachment 96031
One of my pet peeves is fuel dockhands who start to untie your boat before you have had a chance to perform a safety check for fumes and run the blowers. In a similar vein, dock hands who do not know how to securely tie a boat up when you pull in for fuel. This seems to be the rule around here rather than the exception. Everybody seems to be in a hurry. By way of contrast, Jacobson Marina in Frankfort has perhaps the best staff on the west coast of Michigan. Leland Harbor is pretty good too. Others, not so much.

Never seen that on west coast

 

[Creekwood]

[QUOTE="Ike, post: 1185284, member: 24735"
And don't ever allow a marina dock hand or a guest on your boat to fuel your boat. Do it yourself so it goes into the fuel fill, not the water tank or a pole socket and into bilge. I investigated far too many boat fires where a dock hand or a guest on the boat put the nozzle in the wrong socket.

View attachment 96255
Rules may have changed, but when i refuel win Gore Bay in the North Channel, there is a requirement that all passengers must be off the boat, and dock attendants refuel the boat. A Canada thing, or a North Channel thing? I believe Little Current is the same but could be wrong about that.[/QUOTE]
It’s the same at our marina. It may be a law or maybe just a marina insurance rule. I prefer it if the marina dock hands do it. They know what they are doing. And I do, but there are a lot of not so bright boaters that would not do it right, would overfill and spill etc.

 

[mnm99]

Sorry, I only read the first page. I can't even believe this is a question someone has to ask. I ALWAYS turn mine on. 4-5 min is better then chancing my life just because of noise. Fuel injected or not.

 

[hottoddie]

In all these back and forth discussions about blowers and explosive fumes I very rarely hear engine room fume detectors discussed. In my opinion they should be required by the CG and insurance companies. I know my insurance company did ask on my questionnaire if I had a functioning fume detector which I do. Many if not all insurance companies require and automatic fire suppression system in the engine room so why not fume detectors. I would never own a gas powered boat without one and I do check it's function a couple of times each year.

 

[hughespat57]

Perhaps even better would be for a cool air duct directed towards the engine intakes so the air they draw in is cooler...but probably just over engineering things....its damn too crowded down there as is!

I may have mentioned this above, not sure, didn't bother re-reading. Yes, don't overthink this one - other than "for fun", of course! The system is already designed to fully meet the demands of the engine. Boat engines operate perfectly well as-is - they don't overheat due to air. Overheating is typically due to lack of water when there's an issue/problem with the cooling water system. Any "improvements" to the intake air system will not result in any measurable gains, if at all.

Also, most (all?) boats have a secondary air exit, separate from the blower exhaust port.

Remember, it's not about what we, as humans, "feel".

True enough in most cases but I just created a thread about ventilation (as opposed to here "blowers yes or no")
Because there is differences for gas and diesel of course. But now I'm not so sure about running continuously.

http://www.clubsearay.com/index.php...gasoline-vs-diesel-and-other-thoughts.102237/

 

[WV 320 Dancer]

Well...The boat is out till Spring now, so I figured I would ask the question, I know it is recommended but in reality who uses the blower for 4 minutes...or at all....??when first starting or underway. With the fuel injected motors of today they do not expel the gas vapors of the past. Frankly the SR blowers are so noisy I will have to replace mine with something quieter for next year..

Blowers are extremely cheep insurance, mine come on before I turn the key and mine come off when I turn off the key.

 

[Groucho]

I never said I don't use them....The thread was to see how many do for a full 4 min...., as I have seen other boats just put the blowers on... start up and pull away from the fuel dock. I have replaced mine with the Jabsco continuous duty blowers which are much more powerful..(draw about 4X more power). and also much quieter. All told about a $500.00 upgrade.

 

[dwna1a]

4 minutes, I’m not sure. I cut them on first before I start getting the boat ready to go. At the fuel dock as soon as the caps go back on.I also open the genset hatch. They are always running while the genset is running.

Ive taken a few extra steps with my system. I installed blowers on my intake side as well. In the FD we used positive pressure to help clear smoke from a fire, so I use both. I also check the vent ducts annually using a smoke machine.

Maybe it’s overkill. As for the noise, the motors only get bad when the bearings are starting to fail. I’d rather hear that than the one of the fire truck coming for my burning boat.

 

[hughespat57]

4 minutes, I’m not sure. I cut them on first before I start getting the boat ready to go. At the fuel dock as soon as the caps go back on.I also open the genset hatch. They are always running while the genset is running.

Ive taken a few extra steps with my system. I installed blowers on my intake side as well. In the FD we used positive pressure to help clear smoke from a fire, so I use both. I also check the vent ducts annually using a smoke machine.

Maybe it’s overkill. As for the noise, the motors only get bad when the bearings are starting to fail. I’d rather hear that than the one of the fire truck coming for my burning boat.

If they all run together you likely don't get much if any positive pressure. But you are overcoming any duct resistance by forcing the airflow. Positive pressure can cause engine odor problems in the cabin, the bulkheads are often not sealed perfectly.

 

[ttmott]

A little of history and engineering reasoning. I spent over 20 years as an engineer in the Coast Guard Office of Boating Safety and sat on the ABYC committee that deals with engine room ventilation. The point with a blower is to prevent explosions. But how do they do that. Many of you may be familiar with the fire triangle. You need three things to start a fire, fuel, air, and a source of ignition. The fuel system regulations deal with preventing leaks and fuel fumes inside the boat. The electrical regulations deal with sources of ignition. And the ventilation regulations provide the air? Why provide?

Explosions due to gas fumes only occur within a short range of air/fumes mixtures. There is a lower explosive limit (LEL) usually 7 parts air to 1 part fuel. and an upper explosive limit: 14 to 1. Below the LEL the mixture is too rich and above the Upper limit it's too lean. What the blower does is introduce more air to keep the air/fuel mix too lean to ignite. So if you do have fumes in the engine compartment, it doesn't go boom. Why then do you turn on the blower for 4 minutes? Time to get the fumes out and air in and make the mixture too rich. The blowers are required to be ignition protected, that is not be the source of ignition.

And as for the vents. Research has shown that even when the blower isn't on (and the engine is not running) air moves in and out through the vents. On most boats there is an exhaust and an intake, but research has shown they can switch depending on lots of factors, outside temp, temp in the engine room, the direction of the wind relative to the boat. So when the boat is standing still, your intake may be the exhaust and exhaust the intake. But when you switch on the blower, it is on the exhaust ( the one that goes down to about 4 inches above the bilge) and the other the intake, which doesn't have that long a hose on it, just long enough to bring air into the engine room.

If you are underway and you switch off the blower, then it depends on the wind. if you're going slow and the wind is from astern, the exhaust may be the intake and vice versa.

Those of you who use the blower to reduce heat in the engine room after shut down, there is also some research (done by the EPA of all things) that shows that engine room temps don't get up much more than about 118 F even when the boat is standing still and the blower is not running.

And for those who think that fuel injection has solved this problem; the fumes can come from multiple sources. Bad fittings, bad gaskets, leaky hoses, leaky fuel pumps. Most fuel leaks are at fuel system fittings.

Any way my apologies for the long post: Just follow the instructions. Run your blower for four minutes before firing up. After you're underway you can shut it off if you like. Definitely check the bilge and run the blower after refueling before starting the engine. A typical scenario with fueling related boat explosions is the operator gets fuel, gets underway, and about 100 feet later it goes up. That's how long it takes to get into the range between the LEL and the Upper limit.

I just read through this thread. Ike - There are a couple of errors here that need clarification:
The "blowers" for flammable vapors like gasoline are to remove or evacuate the vapors and exhaust to the outside of the boat not to add or blow oxygen into the area to create a too lean to burn condition. The last thing someone would want is to move low lying (heavier than air) vapors to other locations in the engine room and thus create a negative situation elsewhere. So for edification in our boats the "blowers" are there to remove vapors to the outside of the vessel. That, by the way, is exactly why the "blowers" are required to be rated explosion proof.
Secondly, it is not the LEL (lower explosive limit) that is the concern but rather the LFL (lower flammability limit). The LEL is an appropriate stochiometric fuel vapor/oxygen mixture to institute a deflagration and consequently a pressure wave or better known as an explosion. The LFL is the minimum mixture of fuel vapor and oxygen to create a flash fire. The LFL is a leaner or richer mixture than LEL.