Bilge Blower - "Intermittent Use Only"?

[friz]

So, continuing my tour through hell (re-build project) I am looking at replacing the bilge blower. Maybe I have not looked at enough of them (internet) but the dozen or so I have state "Intermittent Use Only". This is my first inboard. I understand that it is best to run the blower anytime the engine is running and not just 5 minutes prior to light-off. I can for see running the engine hours at a time. Is my understanding correct? Maybe I need a more precise definition of "Intermittent Use Only".

[valhalla360]

It doesn't hurt to run the blower but once the engine is running, the engine is a giant air pump pulling air from the engine room and sending it out the exhaust.

At speed the engine is moving far more air than your typical blower will move.

[wingless]

My boat has these Shurflo 4" 220 cfm blowers that are rated for continuous duty.

Note that the circuit protection must be followed per the instructions.

[wingless]

Originally Posted by friz

So, continuing my tour through hell (re-build project) This is my first inboard. I understand that it is best to run the blower anytime the engine is running and not just 5 minutes prior to light-off. I can for see running the engine hours at a time. Is my understanding correct?

It is best to follow the boat manufacturer's instructions.

The recommendations in this Shurflo Manual are well written.

BEFORE STARTING ENGINE:
Check engine compartment for gasoline or vapors.
Operate blower for 4 minutes and re-check engine for gasoline vapors.
Do not operate while refueling.
Run blower below cruising speed.

To recap, stick your nose in the engine room to smell for gasoline. Resolve any gasoline problems before proceeding. ALWAYS run the blowers before starting.

For refueling, gasoline is heavier than air. Close all hatches and turn off all blowers before refueling. Do not create a path or draw gasoline fumes into regions. NO SMOKING. Once fueling complete, inspect for fumes, then RUN THE BLOWERS. I turn them on when I go to pay, to get plenty of run time.

Low speed blower operation is frequently recommended. At low speed airflow into / out of the engine room is less than at higher sped operation, increasing the risk for gas fume accumulation.

[S/V Alchemy]

For added security, you can do all the above, and add a gasoline/propane "sniffer" with a banshee alarm to alert you to fumes or even a spill in the engine compartment. I had an Atomic 4 for years with the detector just beneath the carb and I would put a gas-dappled rag beneath it to test it...it worked!

This is the model I had: ELECTRO SYSTEMS #GS/7, GAS & PROPANE DETECTOR/CONTROLLER. The Chandlery Online

[Cadence]

I didn't notice. Diesel or gas. With a diesel run it before start with gas it would not hurt. a bit, to have it as continuous duty.

[a64pilot]

I've not seen a Diesel with a bilge blower?
Mine has a blower that has its intake up high to remove heated air, but a bilge blower meant to remove combustible gasses has it's intake down low in the bilge where the gases would build up

[friz]

Sorry, it's gas, Chrysler Marine 318. That is some good info. Like the idea of a "sniffer".

[Cadence]

Originally Posted by friz

Sorry, it's gas, Chrysler Marine 318. That is some good info. Like the idea of a "sniffer".

Use a continuous duty. Gas vapors will burn you to the waterline.

[HopCar]

Valhalla is correct. Once you start the engine, it is going to be moving far more air than the blower. No need to run the blower once the engine is running. That is why so many bilge blowers are rated for intermittent use.

If you want to spend the money, there are continuous duty blowers available.

[wingless]

Originally Posted by a64pilot

Mine has a blower that has its intake up high to remove heated air, but a bilge blower meant to remove combustible gasses has it's intake down low in the bilge where the gases would build up

One of the modifications I made to my boat was the addition of a thermostatically controlled heat exhaust.

My boat has a characteristic problem w/ heat soak / vapor lock where the thermal mass of the engines within the highly insulated engine room cause the engine room temperature to rise once the engines are shut down, unless the engine room is manually opened to external air after the engines are shut down. The temperature will climb high enough to prevent the engines from running properly.

My system maintains the selected temperature by running a second set of these Shurflo 4" 220 cfm blowers with a high intake that prevents vapor lock.

My boat has the low intake blowers for gas fumes and high intake blowers for heat extraction.

It isn't possible to run all blowers at once or the hull will implode like an egg shell.

[meridian28]

I know of an intermittent unit that was left on, overheated and shorted out and caused a minor fire. Diesel engine.

[sotavento]

I have a Vetus Vent 76 Blower in my Beneteau F456 and is gone bad so I have a similar question. When I look at Seaflo In Line Bilge Air Blower 130CFM it's specs say intermittent use only" so question arises what means it in this context. May be intermittent because a blower normally works for days and days?. I need the blower to work when engine is working otherwise inside the boat there is diesel smell. (apart from security questions). I tend to believe intermittent in this context means NOT forever.

[wingless]

Originally Posted by sotavento

When I look at Seaflo In Line Bilge Air Blower 130CFM it's specs say intermittent use only" so question arises what means it in this context. May be intermittent because a blower normally works for days and days?

When I look at their web site and their manual I don't see the Intermittent Duty specification.

Where is that listed?

[wingless]

My custom High-Volume / High-Pressure air compressor system also uses one of these Shurflo 4" 220 cfm blowers for forced-fresh-air cylinder head cooling during operation. That custom design is so effective that I can grab onto the cylinder head while the motor is operating with my bare hand.