Newbie - Guidance on Blowers and blower hose placement

[FrankyB]

I recently purchased a 1989 Four Winns 315 Vista from a liquidator and I'm restoring it. There are 2 blowers in the engine compartment that are disconnected and I need some guidance to replace and install them with new hoses as some things do not make sense to me. I will post pictures tomorrow.
Here's the scenario:

• There are four vent holes on both the port and starboard sides that the 4" hose are attached to (8 in total). Two of the hoses, on each side, laid at the back of the engines in the bilge. one of the hoses on each side laid at the front of each engine. The other two hoses (one on each side) were just laying in the compartment. No hoses were connected to the two blowers.
• Both blowers were mounted on the port side bulkhead.

Questions:
1. Should both blowers be located on one side?
2. Should both blowers be exhausting or, should one be drawing in air? And, if the latter, how should the hoses be configured?
3. Should the hose connected to the blower be from the front of the engine or the rear? (Assuming at the lowest point in the bilge?)

Thanks!
Frank

 

[GA_Boater]

Waiting for the photos. You know - A thousand words and all that stuff.

Blowers are always for exhausting the engine compartment. I don't recall seeing any that blow into the compartment.

 

[alldodge]

My Formula has two blowers (one on each side) and they suck air out of the bilge and up thru the vents.

Port side, one goes from hose even with the side of the block, thru blower, then out vent. Other side of port vent goes to below the motor in the bilge area.

Starboard side same as port except hose goes thru blower and hose is under the motor in bilge area. Other side does not have a hose on it

 

[FrankyB]

Thanks AllDodge. A co-worker suggested that I also call a blower manufacturer and ask if they have a science to this. I have dual King Cobra 465s. I got to believe that their is some reasoning that they have 4 hoses per each motor. Otherwise, I may try to replicate how yours is set-up but with a few additional hoses.

Frank

 

[wrench 3]

The air volume that you need to get in and out depends on the total volume of the engine compartment. It has to completely change the air in the compartment within the four minute blower time before start up.
My 26 foot also has one blower on each side. With your larger boat and the number of hoses I'm wondering if it may have originally had two blowers on each side. You need the same number of hoses for intake and exhaust. The ports in the boat will be louvered or located such that with the boat going in a forward direction half of them will have air pushed in through them and the others will suck out. The inlet hoses should go to a level just below the flame arresters (air cleaners). The hoses to the blowers should be as low as practical in the engine compartment without any chance of picking up bilge water. Front to rear doesn't matter to much as long as they're not too close together.

 

[FrankyB]

No Title

Thanks Wrench! I've posted two pictures...one is the outside of the boat where a louvered trim piece fits over the holes and a pic of where the 4 vent hose connections are within the vent areas (same on both sides). If your logic is right (inflow vs outflow), than would it make sense that the "inflow" hoses would be attached to the vertical hole and the exhaust hoses be connected to the horizontal holes?.

 

[wrench 3]

While convection flow might have some affect on vertical as opposed to horizontal ports. I believe that the louvers will be a more determining factor. If all four ports on each side go into a common chamber, you may need to have intake on one side and exhaust on the other. If the blower capacity is adequate, I suppose you could have two blower vents and two natural vents. But I,d be worried that the blowers would blow air back down the natural vents.

 

[FrankyB]

All four vents do share a common chamber. I, too, have the same concern as you do. I'll be back in Charlotte this weekend and will check the louvers (but I think they are all straight).. Perhaps at that point, and with this knowledge at hand, I need to call the technical support from one of the blower companies and get their take. Stay tuned! Thanks for joining in...
Frank

 

[alldodge]

Side vents on my Formula are the same

 

[FrankyB]

Side vents on my Formula are the same

Do your side vents have both vertical and horizontal hose connections similar to my pic??

 

[alldodge]

Do your side vents have both vertical and horizontal hose connections similar to my pic??

Mine are just vertical. In the old days boats were built so air would be funneled into the engine compartment when running. These days they don't use this method so much, the engine once running pulls in a lot of air on it's own. Owners manual still says to run blower at slow speed but not many including myself does it

 

[FrankyB]

Well....this has been quite the journey. Unless I'm just missing it, there is little information available via google regarding the sizing and configuration of both ventilation and fume exhausting. I've reached out to the engineers at Rule and waiting their response. What I did find surfing the net is a great article on engine room ventilation and the ramifications if one changes the ventilation unknowingly by making some type of engine room modifications. It does also give credence to using multiple blowers, some drawing air in and some exhausting. I'm not yet certain what is the best design for my situation but this article has taught me a lot. The article is fairly lengthy but informative. Here is the link:

 

[Grandad]

I think each vessel has its own circumstance. The original problem with the PassageMaker as reported in the link above is that there was negative pressure within the engine room, making it difficult to open the door. From a safety standpoint, negative pressure in a hazardous location is a good thing. Any leakage between the engine room and the surrounding area will be fresh air entering the hazardous location creating no problems. If on the other hand, you were to force air into a hazardous location, creating a positive pressure, any hazardous vapors inside will take any and every means of escape, possibly into the cockpit where ignition sources abound. That's my logic, anyway. - Grandad

 

[wrench 3]

If you can't find any official information on what equipment is needed, I'd measure the volume of the engine compartment (Probably just going with maximum depth, width and length) subtracting the volume of any large water tanks etc. Then figure out how much CFM you need to remove that much air in four minutes. Blowers usually list their CFM and whatever hose sizes they need, use at least the same for intake.

 

[FrankyB]

. Any leakage between the engine room and the surrounding area will be fresh air entering the hazardous location creating no problems. If on the other hand, you were to force air into a hazardous location, creating a positive pressure, any hazardous vapors inside will take any and every means of escape, possibly into the cockpit where ignition sources abound. That's my logic, anyway. - Grandad

Grandad - that would be my reasoning too. What I'm concluding is there are two objectives: 1. exhaust any potential fumes from the engine compartment, 2. provide enough air intake to maintain an adequate engine compartment temperature. I now understand from you and others that I need to provide enough CFM to address objective #1. As it relates to objective #2, I'm still not certain what I need to be doing. I know there are 8 vent hoses/holes and 2 blowers so I'm assuming that 2 of those 8 holes are used by the blowers and, both blowers are exhausting. I'm also assuming that FWinns engineers had a specific reason in mind for what to do with the other 6 hoses. My last assumption is those 6 remaining holes are used for either/both air intake hoses or natural heat exhaust hoses given that air rises.I've yet to be able to locate another 315 vista owner to learn how the configuration is in their boat. The placement of these remaining hoses is now the main challenge.

Frank

 

[FrankyB]

Thanks Wrench. I will measure as you suggest and determine what my blowers are capable of. My challenge still remains as I stated above in my response to Grandad.

Frank

 

[Grandad]

If you don't get a definitive answer, I think your summary of the 2 objectives may be your only guide. Since fumes fall and warm air rises, one has to choose which direction is the most important. You can't have it both ways. For what it's worth, the engine intake draws from a higher location and draws more air as the engine works harder and produces more heat. Measuring the temperature might allay your concern. - Grandad

 

[DeepBlue2010]

I think you are over thinking this to death. Do you have an engine room or an engine compartment? My guess is it is an engine compartment at the stern of your boat. I would start first by trying to know for sure what was the original configuration of the boat. Did you have two blowers on each side or one on each side with two hose ports or what.

At rest, the engine compartment is not capable of ventilating itself that is why you need help from power blowers. Normally, on each side you will find ports attached to blower(s) and others attached to jusy hose not connected to anything or without hose. Again, at rest, like if you are in the marina getting ready to leave or at the gas pump, etc, you turn on your blower, air gets sucked out from the port that is connected to the blower and replaced by the free floating port. In an engine compartment, you can't create vacuum inside, the open ports will not allow you to. While in engine room, you theoretically can.

Now as you speed up, the speed of the air layer the is touching the louvers from outside the boat is much faster than the one inside the engine room. As a result, the pressure kn the outside will be much less than the engine compartment which causes the air to move from the high pressure area to the low one. In other words from inside the engine compartment to the outside. Theoretically, if the air pressure inside the engine compartment drops to the same level of the outside pressure, the flow will halt. And if it drops below it, the flow will reverse. This happens in your car if you are smoker and roll the window slightly down, your smoke get sucked out without you directing your mouth to the window trying to force it out. It is also why the wing creates left on an aircraft but this is a different story. Long story short, at speed, you have a self regulated smart pump powered by the laws of physics not by batteries.

You dont have to direct the louvers to scoop air in. The aerodynamics work without it. Just a regulare horizontal louvers pointing down will do. Even the vertical louvers I saw on boats are not facing foreard to scoop air in, the are pointing backwords not to disturb the natural aerodynamics above.

Forgive me if I told you something you already know or if I misunderstood your ask. I am only trying to help.