outboard cooling system troubleshooting

Matt B

Matt B

RAMONES
Forum Supporter
I got antsy waiting for a used Yamaha 8hp outboard to appear, and jumped on what seemed like a deal on a Honda BFD9.9. Test run without water. I never should have done that. Turns out it won't pee water out the cooling system indicator. I replaced the water pump impeller. The old one was definitely trashed. But it still isn't moving water, being tested with a hose and muffs over the lower unit intakes, (which I cleaned). What do you think should be my next move? Replace the thermostat? Try running it in a tank or in real water first (no muffs)?
 
Check the pee hose. Pull it off of the nipple (pee fitting) where it exits the lower cowling. I've had more than one outboard plug or dribble because sand/salt accumulated right there at the very end where it gets constricted by the nipple (ID nipple < ID hose).
 
Run a piece of hard wire (clothes hanger, or heavy electrical) up the urethra. o_O
Mud daubers like to build their nest in the pee hole tube.

It can be difficult to have enough water pressure/volume using the water muff to make it pee.

If you have access to putting it in a tub or take your watercraft to a boat launch works well.

Might also want to check the water thermostat. Just remove it and test by putting it into a pan of water on the stove and observing if it opens as the water heats up.
 
Yup what is said above. I’ve heard of the old redneck truck of using thick weed whacker string (and keeping some with ya in your toolkit). It’s often strong enough to dislodge the blockage but not too stout to damage anything.

Hope it’s a simple fix!
 
Thanks all. I should’ve mentioned that I looked at the pee hole outlets but haven’t put anything in them to make sure they’re open. There are two, side by side, and one is see-through and one is black. The transparent one passed visual inspection for any blockage. I’ll have to look more closely at probing the black one.
 
In The Keys where I was always running shallow and there is a good deal of grass/vegetation in the water I always had a piece of weed whacker material looped to the back leg of the poling tower. The pee hole would sometimes become clogged and it is not a good idea to try to clear it with a potentially sharp metal wire but the plastic string was stout and flexible enough to safely get the job done.
 
Chances are it's a blockage in the pee hole tube. If that is the case, water is still cooling the motor. You can have no water coming out the pee hole and still have water running through the jacket.

I would run it in a barrel. There are at least 2 different sized earmuffs. If it is the wrong one (too big), you won't pick up enough water to correctly test it. I have had this happen to me.

The thing that you have going for you is that it's a 4-stroke and therefore a bit cooler running than a 2-stroke. Don't push it, but try not to sweat the fact hat this happened. You likely have not ruined anything yet.

I would consider changing the thermostat either way provided it's an easy fix. Most are uber-easy from my experience.

If you get it fixed, consider using salt away when you flush it, if you run it in salt water.

Make sure that you turned the impellor correctly when you installed it. Read the Heloc manual again and just make sure that it was installed properly.
 
I assume that this isn’t one of those motors that doesn’t piss until it gets up to temperature and the thermostat opens.

If the old impeller disintegrated, you could have bits of impeller all through the cooling system, which would be a problem. On Mercs you can hook up a hose and back flush the system. If you can do that, you should.
 
Update: I took some lawnmower string to the pee holes as suggested. When I retrieved it from the opaque black one, it came back wet. This seems promising to me. Like maybe there just wasn't enough pressure with the muffs, or the thermostat just was not open yet.

Chucker said:
I assume that this isn’t one of those motors that doesn’t piss until it gets up to temperature and the thermostat opens.
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I don't know! I've never seen it running properly and I can't seem to find this answer, though I've looked a bit. I had the same thought, though. I mean, what's the point of the thermostat if it doesn't close when the motor is cool?
charles sullivan said:
Chances are it's a blockage in the pee hole tube. If that is the case, water is still cooling the motor. You can have no water coming out the pee hole and still have water running through the jacket.

I would run it in a barrel. There are at least 2 different sized earmuffs. If it is the wrong one (too big), you won't pick up enough water to correctly test it. I have had this happen to me.

The thing that you have going for you is that it's a 4-stroke and therefore a bit cooler running than a 2-stroke. Don't push it, but try not to sweat the fact hat this happened. You likely have not ruined anything yet.
Click to expand...
I'm not too worried. My first test run, it almost immediately was running at a governed low speed, which is a design feature when oil pressure is low or if it runs too hot. (Oil system seems fine)

charles sullivan said:
I would consider changing the thermostat either way provided it's an easy fix. Most are uber-easy from my experience.
Click to expand...

Pulled it off. Very easy. It was nasty. New one should arrive tomorrow.

charles sullivan said:
If you get it fixed, consider using salt away when you flush it, if you run it in salt water.
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Good call.
charles sullivan said:
Make sure that you turned the impellor correctly when you installed it. Read the Heloc manual again and just make sure that it was installed properly.
Click to expand...
Yeah I'm pretty sure I did this correctly but it's a good one to remember, just in case.
Chucker said:
If the old impeller disintegrated, you could have bits of impeller all through the cooling system, which would be a problem. On Mercs you can hook up a hose and back flush the system. If you can do that, you should.
Click to expand...
I found all the impeller wheel bits, by counting them. Every single one was sheared off. Most were up near the impeller but I found some remnants inside the intake screen down at the bottom of the lower unit.

Once I get the new thermo and get it in, I plan to test run in a tank. Thanks again, all.
 
Matt B said:
I found all the impeller wheel bits, by counting them. Every single one was sheared off. Most were up near the impeller but I found some remnants inside the intake screen down at the bottom of the lower unit.

Once I get the new thermo and get it in, I plan to test run in a tank. Thanks again, all.
Click to expand...
Rubber impellers do get brittle and break, as you've discovered. Something I learned the hard way (this is a bit embarrassing), never start the motor without turning on the water to your flush kit. I think starting the motor and not getting the rubber implellers water lubricated immediately creates friction that can tear/shear the impellers.
 
Well, I installed the new thermostat and ran in a garbage can and it still is not working correctly. Some drops of water did periodically dribble out of one of the pee holes (the one that had the weedwhacker string come back wet) and I could feel hot moist air coming out of that one, too. This has me thinking back to @Chucker 's comment that there may be more impeller bits (or anything else in there) blocking good water flow. I'm thinking that water is trying to get through but can't because it is blocked somewhere. And so I want to backflush the system.

There is a way to flush the system from the top, but of course it requires a fitting for garden hose to motor that I ordered and should be here in yet another week. Where that fitting attaches is right above the thermostat, and part of the same plastic housing. I'll upload some pics in a bit. But I am tempted to just pull the thermostat off again and flush with the garden hose spray gun through that hole. Is there any reason not to do it this way? Could I get too much pressure through the system doing that?

The fitting for the garden hose attachment is pretty small diameter, like 3/8" so I imagine that will be a pretty low pressure flush. But I'm thinking I kind of want a bit of pressure to dislodge any crap.
 
Try again in a barrel but give it a little throttle. I've owned/repaired/sold many outboards and some just won't start to pee until a little throttle is given to "prime" the system.
 
Mtnwkr said:
Try again in a barrel but give it a little throttle. I've owned/repaired/sold many outboards and some just won't start to pee until a little throttle is given to "prime" the system.
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Thank you for the suggestion. I did try that.
 
If you have a compressor uou can also use air to try and back flush any foreign piesces of the old impellor out the system. Youre gonna have to remove the lower unit if that is where the impellor is housed first. Hope this works.
 
CRO said:
If you have a compressor uou can also use air to try and back flush any foreign piesces of the old impellor out the system. Youre gonna have to remove the lower unit if that is where the impellor is housed first. Hope this works.
Click to expand...
I do have a compressor and I think I'll try that. Thanks for the suggestion.
 
I think I am also going to remove the lower cowling, or at least the one side of it, so I can really get to those little pee hole tubes, remove them from connections on both sides (hopefully) and really make darn sure they are completely clear.

Ugh, I hate working on motors. I spent my youth working on my crappy cars out of nece$$ity, never enjoying it although it is satisfying to complete something.
 
Yeah - way more fun to work on motors because it's something you decide that you want to do as opposed to something you have to do.
 
Today I took the lower unit off again, took the thermostat out again to open up that area, and removed the starboard side lower cowling so I could access the two tubes that have outlets on that side. The clear one which has never shown any type of water is connected to the fuel system/carb. I think it's some kind of breather tube for fuel/combustion and not related to my issue.
Then I powered up the ol' Harbor Freight compressor and blasted through every access, including from the tube to the lower unit (from the bottom up), and in through the thermostat and flush port area, and from the pee tube outlet back in. When I did that, I could feel air coming out of the thermostat area. Same for when I blasted air up tube that goes down to the lower unit. Everything seems pretty clear. There was water on the close side of the thermo, and in the pee hole outlet tube. Water is in there, it just is not flowing. But in case water can move something that air cannot, I will wait for the flush port fitting to arrive and flush with water from the garden hose (from the top) that way, and then test in the tank (garbage can) again. Fingers fricken crossed. If it still doesn't work after that I guess I'll do like @charles sullivan suggested and disassemble and check my new impeller assembly.
 
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