ear muffs, impellers, water intake amounts, and related

[flywelder]

Wondering, and seeking answers to these questions:
when running a boat engine, either outboard or I/O out of the water because your working on the engine, will 'muffs' provide enough water,?
and enough water to start and run the motor to test the repair (s) ? and still not damage anything??
and does the impeller, still pump water through the engine, when the water source is 'muffs'?

 

[tpenfield]

Wondering, and seeking answers to these questions:
when running a boat engine, either outboard or I/O out of the water because your working on the engine, will 'muffs' provide enough water,?
and enough water to start and run the motor to test the repair (s) ? and still not damage anything??
and does the impeller, still pump water through the engine, when the water source is 'muffs'?

1) when running a boat engine, either outboard or I/O out of the water because you're working on the engine, will 'muffs' provide enough water,? = YES

2) enough water to start and run the motor to test the repair (s) = YES

3) and still not damage anything?? = YES

4) does the impeller, still pump water through the engine, when the water source is 'muffs'? = YES

Not sure what the concern is . . . . :noidea: A garden hose & muffs will provide enough water to run the engine at an idle speed and even a high idle for a short amount of time. I usually test small outboards in a trash can full of water, and I/O's and large outboards using the ear muffs.

 

[Scott Danforth]

remember, when running an outboard or IO on muffs, you are limited to 1500 RPM or less. because most garden hoses do not supply enough flow.

a typical raw waterpump impeller will flow up to 25gpm a typical garden hose will supply about 12-15 gpm, hence the recommended limited RPM

what is the concern that promps your question?

to expand upon Ted's trash can comment, you can usually run 40hp motors and below in a large garbage can, however you can never run a large outboard or an I/O from a garbage can

 

[dingbat]

remember, when running an outboard or IO on muffs, you are limited to 1500 RPM or less. because most garden hoses do not supply enough flow.

a typical raw waterpump impeller will flow up to 25gpm a typical garden hose will supply about 12-15 gpm, hence the recommended limited RPM

How do you get 25 gpm thru a 1/2” water pickup tube?

 

[racerone]

The RPM limit is there because it is bad for a 2 stroke to run at high RPM in neutral !!

 

[Scott Danforth]

How do you get 25 gpm thru a 1/2” water pickup tube?

I never stated outboard or I/O. not all pickup tubes associated with raw water pumps are 1/2", some are smaller, some are larger. for example, the raw water pump plumbing for an AQ series of VP outdrives is 1-1/4"

 

[flywelder]

Thank you to each of you, great answers!! My reason for asking and m the source of my concern stems from s an article or statement I read some where, and I don't recall where, I wish I did. The article or words, said something about the impeller doesn't work when using muffs. Now after reading your replies, perhaps the author was referring to having something to do with inadequate water supply?
I did not know about RPM limits!!! very glad you included that info!!!

Now, what if the motor [a 4 cylinder, mercury mercruiser motor] utilizes a 'radiator / water tank' device, to cool the antifreeze that circulates in the motor, does that change any of your replies? Does such a set up require different, or added requirements? and concerns?

I suspect that such device is installed in some boats, so boat can be used in either fresh or salt water? Am I correct?

 

[racerone]

On a hose the impeller spins so that the water from the hose can find its way into the block.-----When motor is stopped the impeller vanes block the water flow.

 

[tpenfield]

Now, what if the motor [a 4 cylinder, mercury mercruiser motor] utilizes a 'radiator / water tank' device, to cool the antifreeze that circulates in the motor, does that change any of your replies? Does such a set up require different, or added requirements? and concerns?

I suspect that such device is installed in some boats, so boat can be used in either fresh or salt water? Am I correct?

1) Now, what if the motor [a 4 cylinder, mercury mercruiser motor] utilizes a 'radiator / water tank' device, to cool the antifreeze that circulates in the motor, does that change any of your replies? = NO it does not change the relies

2) Does such a set up require different, or added requirements? and concerns? = NO concerns

3) I suspect that such device is installed in some boats, so boat can be used in either fresh or salt water? Am I correct? = PARTIALLY . . . A 'closed cooling system' provides protection to the engine internals, because it isolates the sea water(or lake water) from the coolant in the engine, making it more like a car cooling system than the traditional boat cooling system. The 'Heat Exchanger' does the job of moving the heat of the engine from the coolant to the sea water. Yes, it is better for use in salt water, but not required . . . many boats that are run in salt water still have the traditional cooling systems, not closed cooling.