Home › Forum › Ask A Member › 9.9/15 impeller housing tricks?
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fleetwin.
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March 11, 2015 at 12:50 pm #902
Back on the old boards I had a post about some cooling issues with an 18/20/25hp motor. Well…now I’m into the 9.9/15’s (10 to go through). Are there any little tricks to be aware of with this type of impeller housing? I looked it over fairly closely, and see there is a hole from leading from the driveshaft orifice into that inner impeller cavity…any other tiny holes I should be aware of to clear out?
I only ask because I have one exhibiting overheat issues…so before I start pulling the head and water bypass cover (here the tell tale stems from), I figured I’d ask this. Seems these motors require powerhead removal to get the side bypass cover off, or at least drilling a hole in the side of the lower cowel to access that front lower hex screw (yippee!!!!!).
March 11, 2015 at 2:00 pm #11811This link has a lot of good information about Johnson Evinrudes of 9.9/15hp breed. He give a lot of good information with pictures and explanations.
http://www.leeroysramblings.com/Outboar … icles.html
March 11, 2015 at 2:25 pm #11812I already looked at his website, it is very good. But there are things he has missing too so I decided to float the question out there.
Im digging deeper into the motor as we speak. It has low water flow; installed a new impeller, made sure all the usual things in the gearcase are in order (clean screen, inlet grommit OK).
The telltale only drips water. With thermostat removed and a garden hose hooked up there is water passing through the thermostat seemingly freely.
Thermostat still opens and closes and appears OK. Since I have no replacement gaskets Ill go ahead with a teardown to inspect closer the inlet/outlet exhaust grommits and telltale bypass area for clogs. Will report back.
This is the 1st full teardown on the 9.9/15’s Ive done so it will be educational.
March 11, 2015 at 3:48 pm #11817I don’t know if this applies to the 9.9/15, but it does to other OMC’s There is a hole drilled at an angle between the water tube/grommet area down into the cup that surrounds the drive shaft. The purpose is to keep the cup filled with water and prevent air from going down past the drive shaft, into the pump. You probably have to remove the grommet to poke something through the hole.
March 11, 2015 at 10:27 pm #11849Those water pumps are fairly simple, yes do inspect the bleed hole in the cup/housing though. Are you using OEM parts? There have been complaints with sierra pump components. The other area to look closely at is the gearcase housing sealing area under the impeller plate. These gearcases are pretty thin under there, the aluminum may have eroded away creating an air/exhaust leak into the pump.
Needless to say, I’m sure you have already checked to make sure to overboard indicator just isn’t plugged up, very common. The crud also gets stuck on the end of the plastic nipple going through the lower pan. I am assuming the engine is actually getting hot, and that you have let it run long enough to confirm this.
What year is this engine? Later 70s models picked up a lousy upper water tube grommet that loves to crush, especially in salt water. There were improvements made in the mid 80s, but the problem still persisted. The early models 74-78 had a different style grommet that did NOT have this problem. Unfortunately, even those early models supercede to the troublesome grommet.
So, once you have checked all the normal stuff, my money says you will be pulling the powerhead.
Sorry
DonMarch 12, 2015 at 1:59 am #11860Donny!!!! and…FRANK!!!
Glad to see you both on here. I was getting lonely. Don, I laughed at the end of your post when you ended it with "sorry." We’ll both have a good laugh at Rocky Hill about this one in about a week.
The motor is a ’78 15hp Johnson. 1 pull starter. It was a salt water motor, however, it’s still in pretty good shape. Believe it or not, every screw was still loose, except 1 head bolt which I twisted off even after heating it for a solid 10 minutes with the torch, and I’m in the middle of drilling it out and retapping. I pulled the powerhead today, inspected both the water jacket where the tell tale is, and pulled the head and thermostat cover.
There really wasn’t anything clogged up in there, the telltale did have a minor blockage (it was dripping water pre-teardown), but I’m still working my way back to figure out where water flow is being impeded. A little pitting in the water jacket baffle. Those gaskets were shot though and I replaced both, they had holes in the wrong places if you know what I mean.
The thermostat appears OK, and before pulling the powerhead I hooked up a hose to the water tube and water passes through the motor freely. However, it seemed that very little water was getting past the thermostat to the exhaust when I ran the motor, and pulling the t-stat cover showed very little moisture was circulating past it. It was only taking a minute to get it to an overheat condition (and I dropped my laser heat gun in the test tank last week without realizing it…then ran a motor with a regular prop and WACK WACK WACK…minced laser gun…so back to ‘ol faithful…the thermomelt stik, which I used everywhere on the motor…thanks for the advice last year FRANK – New laser gun on it’s way from ebay).
I ran some weedwacker wire up the tell tale a few times before posting this yesterday, and also ran the motor a few different times and the same overheat condition was happening. The impeller is OEM. Impeller housing has a metal cup inside of it (I’m guessing this was normal for these, whereas I’ve seen that as an update on some smaller motors i.e. 2hp).
The grommet on the exhaust tube appeared OK, not folded in (a little tired, but still serviceable). So once I have the cylinder head on, I’m going to try running the motor with no thermostat. I think somehow that it isn’t opening at all. What’s strange is it isn’t stuck, but I can these fail to open after awhile? It’s probably an original although it appears OK (even the gasket is still soft). Either it’s that, or something going on in the gearcase that I missed. When I replaced the impeller, it appeared that there was a very thin gasket between the housing and the steel plate underneath it. This gasket appeared worn, but I figured with all 4 housing screws tightened down that the gasket was basically overkill. The other thing – to confirm – there is no water bypass on these motors? I put my thumb over the empty thermostat hole when I was running water through the motor from the garden hose and it pressurized the water system and effectively cut off water flow. Of course, the tell tale started firing water out rapidly.
I’ll double check the impeller housing, but FRANK…I removed the water tube grommet at the impeller housing and apparently this motor does not feature that slanted vent hole. There was no access hole that I observed (unless I overlooked one through where the ‘ears’ on the grommet are) to do a clean out. I sure hope this wasn’t the issue, because I may have created a lot of work for myself over nothing…but I do know these motors inside and out a lot better then I did 24 hours ago (should come in handy because I have 9 more to go through!). There is a hole on the outside of the housing which leads to the impeller cavity. I am assuming this is set up to accomplish the same as the 18-20-25’s.
March 12, 2015 at 10:39 am #11870OK, well the 1978 models still had the good upper water tube grommet, so reuse what you have it is original! The replacement will be the bad grommet.
There was no gasket used on these engines between the impeller plate and gearcase, so am concerned about what you have going on there. I’m assuming the gearcase to impeller plate mating surface is OK also. Is the block badly discolored from overheating? The only other thing that comes to mind is perhaps the water intake screens are plugged with test tank debris, or perhaps barnacles on the inside if the engine was left tilted down in the water.
At this point, I would probably purchase a complete OEM water pump kit, with the housing. A stuck thermostat would surely cause an overheat as well, the only "bypass" on this engine is through the small bleed hole/notch on the thermostat. Does it look as though this engine has been messed with before (head gasket/exhaust gaskets)? Post some pictures here if you can. DonMarch 12, 2015 at 11:59 am #11871Let me get it back together today and try running it. My hunch is either a bad thermostat disallowing water to flow, or an impeller housing issue. Will report back.
On a side note I picked up an old dual shifter box for twin setups last night for cheap…I think these are fairly rare?
March 18, 2015 at 3:01 am #12225Well in the process of trying to get things back together, it will be necessary to replace the thermostat gasket, so I am just waiting for the part to come in. My money is that the thermostat was stuck closed. I hooked up my test hose to the water inlet/copper tube and it was gushing through both the tell tale and thermostat orifice once I cleaned everything out.
Pre-teardown, I had some dripping and occasional squirts out the tell tale, and that was even before I replaced the impeller (the original was frozen onto the drive shaft…had to use a grinder to get it off the driveshaft and break it loose). It had two paddles bent backwards permanently and still was somehow pumping a fair amount of water, but obviously was in need of replacement.
My guess being a stuck thermostat (closed), is further supported by the fact that today I was working on a completely separate 9.5 (not a 9.9), and that motor was pumping lots of water but overheating. Shut her down, removed the thermostat, and voila! No more overheating (ran cold of course). So now just waiting for a new thermostat for BOTH motors……
As frank said in the old forums…school of hard knocks. First 2 motors I’ve seen with thermostats which open freely in my hand, but fail to open during operation. Thank god for laser heat thermometers.
March 18, 2015 at 1:43 pm #12238You mention that the engine would give an occasional squirt from the telltale, did it ever puff steam out of the telltale? I am asking only because this was usually a good indicator for me (way back in the day) that the upper water tube grommet was crushed. But, you have mentioned that grommet is OK.
Please correct me as I review what I am recalling from your posts. You have had the thermostat out and checked it in hot water? I do remember something about your pyrometer taking a swim though. Most of the OMC thermostats have a little bleed hole/slot allowing a bit of water to "bypass" it. So, I’m thinking that a stuck (closed) thermostat would allow some water to flow from the overboard indicator in most instances, even though the engine would eventually overheat.
Have you replaced the water pump since the first time you had the gearcase off?
You have had the powerhead and the inner exhaust tube off, found no grommet problems.
You had the thermostat out, but have you had the cylinder head off? -
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