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Author Topic:   Running Motor with Garden Hose

Donzi posted 05-27-2011 08:35 AM ET (US)
What is the RPM limitation for running a 2002 Mercury 90HP FOURSTROKE on a garden hose in my driveway? I may rev it up to 3,000-RPM for a few seconds but don't over do it. I never run it more than five minutes including idling time. I just heard the only negative may be generating excessive vibrations on the motor. It runs cool so temperature is not a [factor]. Thanks--Dan
jimh posted 05-27-2011 09:49 AM ET (US)
The lack of any back pressure on the exhaust when running the motor out of the water often changes the running characteristics.
A2J15Sport posted 05-27-2011 10:17 AM ET (US)
No load and no backpressure are the [concerns]. I would not rev the engine.
Donzi posted 05-27-2011 10:58 AM ET (US)
I just run it to make sure I am running on all four cylinders before I take it to the lake. My recent [running problem] was it ran fine at idle but not at 2,500-RPM since one of the fuel jets was clogged.
Slick 50 posted 05-27-2011 11:38 AM ET (US)
I have read and been told in the past that it is very bad for the drive system of an outboard to rev it while out of the water. Without a load it can cause damage to the gears. This could be wrong but is what I understand and practice.
Rick
weekendwarrior posted 05-27-2011 12:06 PM ET (US)
As long as the motor gets plenty of cooling water and isn't over revved then it is fine on the hose. Some motors will draw more than the hose supplies if you rev them up so you have to watch for that. Sustained no-load high-RPM will generate heat so don't sustain high RPM. But a blip or two will do no harm.
Tohsgib posted 05-27-2011 02:11 PM ET (US)
My Suzuki [will] hit a rev-limiter at 3,000-RPM in neutral. A blip to 3,000 is not going to hurt it. What does hurt it is when people take a two-stroke and rev it to 6,000-RPM. Two-strokes just don't return to idle like a four-stroke. They go ding-da-da-ding-da-da-ding etc for a few seconds before they idle down. That is not great for it.
Donzi posted 05-27-2011 02:55 PM ET (US)
I heard it was less stressful on a 2-stroke versus a 4-stroke when running it in the driveway. For some reason, the internal design of the 4-stroke produces greater vibration.
weekendwarrior posted 05-28-2011 06:29 PM ET (US)
I have never heard of vibrations being a problem when running a motor on the hose.
Donzi posted 05-28-2011 09:53 PM ET (US)
A certified Mercury technician told me about the vibrations when running a 4-stroke out of water. I noticed it more so above 2000 rpms.
Binkster posted 05-28-2011 10:28 PM ET (US)
Well that doesn't make any sense. My 3 cylinder 25 Mercury 4 stroke runs as smooth as my car engine at any speed on the hose. Did you ask him why yours would vibrate.
fno posted 05-29-2011 12:19 AM ET (US)
Why would you want to rev the engine on a hose??? Nothing but bad can come from too much of that. That's why most dealers have a tank for the prop to turn in. Once or twice for a short time is most likely OK, but I wouldn't make a practice of it for a few seconds or more. Put it in a horse trough if you want to rev it for more than a few seconds on the hose, and keep the hose on the intake. The horse trough will cavitate and the motor will run dry.
lakeman posted 05-29-2011 08:07 AM ET (US)
I have always, in all my motors in the off season or non use periods, run my engines all types of all sizes(2 stroke) on the hose attachment, mostly at idle speeds, but bump it up once in a while to about 2.5 k rpm for very very short burst. I usually run it for not less than 15 minutes at least every 2 to 3 weeks, getting a complete change of gas and a little cleaning effect, I guess. In all the years, since the flushing device hit the market, I have never had a gas, carburetor or fuel injector/fuel rail problem, maybe I am just lucky.
Donzi posted 05-29-2011 10:14 AM ET (US)
I just had carburator issues due to running ethanol gas, not taking out the 27 gallon Pate tank out sooner, and not running the motor more frequently. Motor runs really quiet and strong with a fresh set of plugs. I just use the garden hose to make sure it will start and run on all four cylinders. The mechanic explained the vibration theory based on the internal design of a 4 stroke along with a "balancer", but I did not take good notes to elaborate on it from a technical perspective.
weekendwarrior posted 05-29-2011 02:29 PM ET (US)
If a motor, any motor, vibrates enough to damage itself, then that is an entirely different problem that will surely require some parts to fix. I have met several well intending mechanics who were not so bright, so I would not take his quote at face value.
moretrench1 posted 05-30-2011 08:07 AM ET (US)
I can add from experience, running a Honds 50 4/S on earmuffs is a problem unless you cover the intake port under the cavitation plate......but the event did get me a new water pump
Jefecinco posted 05-30-2011 10:51 AM ET (US)
After 35 years in the Army I learned that if all else fails it is useful to read the manual. We even had a little acronym which was often used with new guys. It is not as well know as SNAFU but we technical types used it often. RTFM soldier!!
Butch
DeeVee posted 05-30-2011 11:10 AM ET (US)
I used to only run my outboards on the hose at idle speed. A few years ago I learned that unless you bump up the RPM above idle, the thermostat may not open, thereby not providing a complete flush of the cooling system.
The engine speed should not be allied over 2000 RPM, and run until water is pumped out of the idle relief holes, just below the power head. You MUST assure that the adapter muffs are positioned properly and that water is getting to the pump.
This seems to have worked well for me over the past few years, as my outboards never see fresh water, except on the garden hose.
If I need to run it for more than enough time to flush it, I have an old city garbage can that is cut out to clear the transom bracket. This works well for adjusting the carbuerators or fogging the power head
Doug Vazquez
Donzi posted 05-30-2011 05:15 PM ET (US)
I had the slip on flusher but went to a flusher that has a rod that slides thru the water intake. No chance of it slipping off when you turn the garden hose on.

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Author	Topic: Running Motor with Garden Hose
Donzi	posted 05-27-2011 08:35 AM ET (US) What is the RPM limitation for running a 2002 Mercury 90HP FOURSTROKE on a garden hose in my driveway? I may rev it up to 3,000-RPM for a few seconds but don't over do it. I never run it more than five minutes including idling time. I just heard the only negative may be generating excessive vibrations on the motor. It runs cool so temperature is not a [factor]. Thanks--Dan
jimh	posted 05-27-2011 09:49 AM ET (US) The lack of any back pressure on the exhaust when running the motor out of the water often changes the running characteristics.
A2J15Sport	posted 05-27-2011 10:17 AM ET (US) No load and no backpressure are the [concerns]. I would not rev the engine.
Donzi	posted 05-27-2011 10:58 AM ET (US) I just run it to make sure I am running on all four cylinders before I take it to the lake. My recent [running problem] was it ran fine at idle but not at 2,500-RPM since one of the fuel jets was clogged.
Slick 50	posted 05-27-2011 11:38 AM ET (US) I have read and been told in the past that it is very bad for the drive system of an outboard to rev it while out of the water. Without a load it can cause damage to the gears. This could be wrong but is what I understand and practice. Rick
weekendwarrior	posted 05-27-2011 12:06 PM ET (US) As long as the motor gets plenty of cooling water and isn't over revved then it is fine on the hose. Some motors will draw more than the hose supplies if you rev them up so you have to watch for that. Sustained no-load high-RPM will generate heat so don't sustain high RPM. But a blip or two will do no harm.
Tohsgib	posted 05-27-2011 02:11 PM ET (US) My Suzuki [will] hit a rev-limiter at 3,000-RPM in neutral. A blip to 3,000 is not going to hurt it. What does hurt it is when people take a two-stroke and rev it to 6,000-RPM. Two-strokes just don't return to idle like a four-stroke. They go ding-da-da-ding-da-da-ding etc for a few seconds before they idle down. That is not great for it.
Donzi	posted 05-27-2011 02:55 PM ET (US) I heard it was less stressful on a 2-stroke versus a 4-stroke when running it in the driveway. For some reason, the internal design of the 4-stroke produces greater vibration.
weekendwarrior	posted 05-28-2011 06:29 PM ET (US) I have never heard of vibrations being a problem when running a motor on the hose.
Donzi	posted 05-28-2011 09:53 PM ET (US) A certified Mercury technician told me about the vibrations when running a 4-stroke out of water. I noticed it more so above 2000 rpms.
Binkster	posted 05-28-2011 10:28 PM ET (US) Well that doesn't make any sense. My 3 cylinder 25 Mercury 4 stroke runs as smooth as my car engine at any speed on the hose. Did you ask him why yours would vibrate.
fno	posted 05-29-2011 12:19 AM ET (US) Why would you want to rev the engine on a hose??? Nothing but bad can come from too much of that. That's why most dealers have a tank for the prop to turn in. Once or twice for a short time is most likely OK, but I wouldn't make a practice of it for a few seconds or more. Put it in a horse trough if you want to rev it for more than a few seconds on the hose, and keep the hose on the intake. The horse trough will cavitate and the motor will run dry.
lakeman	posted 05-29-2011 08:07 AM ET (US) I have always, in all my motors in the off season or non use periods, run my engines all types of all sizes(2 stroke) on the hose attachment, mostly at idle speeds, but bump it up once in a while to about 2.5 k rpm for very very short burst. I usually run it for not less than 15 minutes at least every 2 to 3 weeks, getting a complete change of gas and a little cleaning effect, I guess. In all the years, since the flushing device hit the market, I have never had a gas, carburetor or fuel injector/fuel rail problem, maybe I am just lucky.
Donzi	posted 05-29-2011 10:14 AM ET (US) I just had carburator issues due to running ethanol gas, not taking out the 27 gallon Pate tank out sooner, and not running the motor more frequently. Motor runs really quiet and strong with a fresh set of plugs. I just use the garden hose to make sure it will start and run on all four cylinders. The mechanic explained the vibration theory based on the internal design of a 4 stroke along with a "balancer", but I did not take good notes to elaborate on it from a technical perspective.
weekendwarrior	posted 05-29-2011 02:29 PM ET (US) If a motor, any motor, vibrates enough to damage itself, then that is an entirely different problem that will surely require some parts to fix. I have met several well intending mechanics who were not so bright, so I would not take his quote at face value.
moretrench1	posted 05-30-2011 08:07 AM ET (US) I can add from experience, running a Honds 50 4/S on earmuffs is a problem unless you cover the intake port under the cavitation plate......but the event did get me a new water pump
Jefecinco	posted 05-30-2011 10:51 AM ET (US) After 35 years in the Army I learned that if all else fails it is useful to read the manual. We even had a little acronym which was often used with new guys. It is not as well know as SNAFU but we technical types used it often. RTFM soldier!! Butch
DeeVee	posted 05-30-2011 11:10 AM ET (US) I used to only run my outboards on the hose at idle speed. A few years ago I learned that unless you bump up the RPM above idle, the thermostat may not open, thereby not providing a complete flush of the cooling system. The engine speed should not be allied over 2000 RPM, and run until water is pumped out of the idle relief holes, just below the power head. You MUST assure that the adapter muffs are positioned properly and that water is getting to the pump. This seems to have worked well for me over the past few years, as my outboards never see fresh water, except on the garden hose. If I need to run it for more than enough time to flush it, I have an old city garbage can that is cut out to clear the transom bracket. This works well for adjusting the carbuerators or fogging the power head Doug Vazquez
Donzi	posted 05-30-2011 05:15 PM ET (US) I had the slip on flusher but went to a flusher that has a rod that slides thru the water intake. No chance of it slipping off when you turn the garden hose on.