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Old 22-01-2019, 02:15   #1
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Mercury 5hp no water flow

So, my tender motor stopped pumping water. No problem I thought. Fitted a new impeller. The old one looked ok but had one fin facing the wrong way. Not enough to be the problem I thought. Turns out I was right. Now with the new impeller I still have no water flow??
Figured I'd ask before pulling the bottom out again.
Any suggestions? A blockage? But where to look?
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Old 22-01-2019, 03:20   #2
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Re: Mercury 5hp no water flow

Is the motor overheating? Did the oil light come on?

When my 2011 Mercury 5 hp 4 stroke stops pumping water the oil light will come on after it overheats.

If it's just your telltale that's blocked, that's different.

Once on my engine, the screen above the prop was blocked. That's the intake on a 2011.
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Old 22-01-2019, 04:38   #3
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Re: Mercury 5hp no water flow

Poke a wire into the pee hole.
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Old 22-01-2019, 05:38   #4
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Mercury 5hp no water flow

First try the witness hole, disconnect it if you have to and blow it out or see if water flows from the fitting.
Keep your old impeller as a spare, a turned backward blade is common, it’s often the motor turning backwards slightly after shutdown.

If you use a wire, use a thin one and fold it over so that your not pushing a sharp cut off end into the hose, cause it may stick at the first turn, won’t hurt anything, but you can’t get the wire in.

A thick piece of monofilament fishing line works too if you have any, also good for cleaning out carburetor jets as the monofilament won’t hurt anything.
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Old 22-01-2019, 08:00   #5
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Re: Mercury 5hp no water flow

We recently had a problem with our outboard; discovered all the cooling passages around the cylinder walls were all salt-encrusted... so even though the water pump was working fine (new impeller and all that) and the witness stream looked good...

No water was actually flowing into the cooling jacket... Had to dismantle and actually dig the salt residue out mechanically.

I learned something about our flushing regime, from that. <sigh>

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Old 22-01-2019, 08:51   #6
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Mercury 5hp no water flow

Quote:
Originally Posted by ranger42c View Post
We recently had a problem with our outboard; discovered all the cooling passages around the cylinder walls were all salt-encrusted... so even though the water pump was working fine (new impeller and all that) and the witness stream looked good...

No water was actually flowing into the cooling jacket... Had to dismantle and actually dig the salt residue out mechanically.

I learned something about our flushing regime, from that.

-Chris


What motor?
I’ve heard a similar story about one of the new Suzuki’s and wondered if it was a one off failure or a trend.
What made you determine you had an overheat? What make you dig deeper?

I almost never flush mine, and think that very common with cruisers, I’ve never seen one flushing a motor.
Fresh water usually isn’t that available.
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Old 22-01-2019, 09:30   #7
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Re: Mercury 5hp no water flow

Quote:
Originally Posted by a64pilot View Post
What motor?
I’ve heard a similar story about one of the new Suzuki’s and wondered if it was a one off failure or a trend.
What made you determine you had an overheat? What make you dig deeper?

I almost never flush mine, and think that very common with cruisers, I’ve never seen one flushing a motor.
Fresh water usually isn’t that available.
I doubt this an engine specific issue. The "salt" accumulation (most likely calcium carbonate) can occur as it drops out of sea water ~>165F. It commonly happens in inboard engines and generators also.

The other possible salt is aluminum oxide from the OB block itself interacting w/the seawater. Excess corrosion will happen when the seawater is left in the OB and not flushed. Its only a matter of time.

Using a safe engine flush to remove the calcium carbonate build up is probably safe to use in OBs. May need to wait longer or use a stronger acid if the salt is aluminum oxide (check w/the manufacturer to see if its safe to use a engine flush or stronger acid in your OB). As suggested before another way to get the salt out is to do it mechanically (ream out the coolant ports) after dismantling the OB.


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Old 22-01-2019, 09:34   #8
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Re: Mercury 5hp no water flow

A bad head gasket can cause the cooling circuit to be come pressurized stoping the water from flowing through.
An overheated engine is a common cause of a failed head gasket.
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Old 22-01-2019, 09:44   #9
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Re: Mercury 5hp no water flow

I had the same problem with my 2-stoke Yamaha 2hp. Had to take the head off and clear the cooling passages mechanically.
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Old 22-01-2019, 10:38   #10
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Re: Mercury 5hp no water flow

Quote:
Originally Posted by Bill O View Post
I doubt this an engine specific issue. The "salt" accumulation (most likely calcium carbonate) can occur as it drops out of sea water ~>165F. It commonly happens in inboard engines and generators also.

The other possible salt is aluminum oxide from the OB block itself interacting w/the seawater. Excess corrosion will happen when the seawater is left in the OB and not flushed. Its only a matter of time.

Using a safe engine flush to remove the calcium carbonate build up is probably safe to use in OBs. May need to wait longer or use a stronger acid if the salt is aluminum oxide (check w/the manufacturer to see if its safe to use a engine flush or stronger acid in your OB). As suggested before another way to get the salt out is to do it mechanically (ream out the coolant ports) after dismantling the OB.


Bill O.


Understood, but a motor’s coolant passages should never reach 165F or really even close on a salt water cooled motor.
However if there was a design flaw, it could, which would lead to the build up, that is why I was wondering what motor.
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Old 22-01-2019, 11:14   #11
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Re: Mercury 5hp no water flow

happens often, spiders crawl into the pee hole, use a wire to unclog it
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Old 22-01-2019, 11:23   #12
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Re: Mercury 5hp no water flow

Quote:
Originally Posted by a64pilot View Post
What motor?
I’ve heard a similar story about one of the new Suzuki’s and wondered if it was a one off failure or a trend.
What made you determine you had an overheat? What make you dig deeper?

I almost never flush mine, and think that very common with cruisers, I’ve never seen one flushing a motor.
Fresh water usually isn’t that available.

Suzuki DF15A, same as yours except horsepower I guess.

The red light came on and it went into limp mode, even though the tell-tale flow looked fine.

Likely caused by... only flushing using the flushing port with the engine not running. IOW, not flushing using a muff with the engine running. Suspect it's because the thermostat probably doesn't open when flushing with the engine off.

Probably exacerbated by not running the thing very often. We've only got about 17 hours on the outboard, over the last 4 years. (Since we lost the big dog, we don't need to go ashore as religiously.)

Salt-Away didn't work, once we were at the point where we discovered the issue.

-Chris
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Old 22-01-2019, 13:43   #13
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Re: Mercury 5hp no water flow

I had the same problem with a Yamaha 3.5 hp engine.

I thought there might be something that had got past the impeller and was obstructing the water outlet. Unfortunately that was not the case for me. Maybe it is for you. Lets hope so.

I stripped the motor and opened it up, finding no protective coating on the inside of the water chambers, and the bare aluminium had corroded and blocked the waterway where it exits. I replaced the thermostat while I was at it. I put it all back together after cleaning it thoroughly, and it worked fine. I had also cleaned the carburetor and fuel pump while I was at it. If you have the engine on a bench, you might as well test and check everything.


Next time I have it apart I will properly coat all the aluminium surfaces in contact with cooling sea water. I will do some research as to the most suitable coating--paint, epoxy, poly urethane etc.
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Old 22-01-2019, 13:48   #14
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Re: Mercury 5hp no water flow

I use a short piece of weedeater string to clean the tube. Works great and does not punch thru the tube.
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Old 22-01-2019, 14:00   #15
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Re: Mercury 5hp no water flow

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Originally Posted by ranger42c View Post
Suzuki DF15A, same as yours except horsepower I guess.

The red light came on and it went into limp mode, even though the tell-tale flow looked fine.

Likely caused by... only flushing using the flushing port with the engine not running. IOW, not flushing using a muff with the engine running. Suspect it's because the thermostat probably doesn't open when flushing with the engine off.

Probably exacerbated by not running the thing very often. We've only got about 17 hours on the outboard, over the last 4 years. (Since we lost the big dog, we don't need to go ashore as religiously.)

Salt-Away didn't work, once we were at the point where we discovered the issue.

-Chris


Yours is I believe the second Suzuki I have heard that has had this issue.
The 9.9, 15 and 20 Suzuki are I believe the same motor, computer is the difference, although I have heard that there is a throttle restrictor on the 15. I didn’t think that though, I thought it was just computer.
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