Water circulation or lack of on 40hp

[heyyou325]

I have a 1984 Johnson 40 hp outboard on my fishing boat. While fishing a week ago I noticed no water coming out of my pee hole. Fairly windy day, with about 16 to 18 inch chop. My fishing buddy and I quickly reeled in our lines, and headed for the dock, about 20 minutes away. I felt the engine several times and it never did seem hot which surprised me. I did a compression test to make sure I hadn't warped anything, 138lbs on the bottom, and 144 on the top. I assumed it was the impeller, about 3 or 4 years old, and changed it. When I restarted it with a flusher, I had the same problem. I noticed the water shooting out of the flusher was probably cut by about 1/3 when I started the engine. It took a lot longer for the water to quit running out the exhaust, and other drain holes in the exhaust housing. I removed the lower unit again, I'm old and arthritic, so unhooking the shifting column under and behind the starter takes awhile. Everything I touched was hooked up correctly. I placed a hose over the water tube with a fairly snug fit and turned on about 20 to 30 lbs of water pressure, and it went up the tube and right back out the exhaust housing. I tried 40 lbs of compressed air, some water misted out the pee hole, but most came right back down the exhaust housing. I cleaned the pee hole out in the beginning, so I know it isn't plugged. I dawned on me it might be a stuck thermostat. I've never changed one on this motor I've had for 8 or 9 years, and can't seem to find it. My SELOC repair manual mentions a thermostat, but says very little about it, and the only diagram with it in shows it on the lower right corner of the powerhead. I can't find anything that looks like a housing for one there. Does anyone have any info on where it is, or what else I should check. With my last 40 hp johnson (1969) I could look up the exhaust housing and see problems, with a flashlight, even pull out the water tube and put it back in. With this one I can't. Any help will be appreciated. Thanks

 

[Chinewalker]

If you ran it 20 minutes back to the dock, you're water pump is working. MOST of the water comes right out the exhaust - that's the way it's supposed to be. Very little water actually comes out the pisser. Are you SURE the pisser outlet is clear? Blowing compressed air back through is a good way to check it. Often, whatever is blocking the outlet gets flushed back into it after clearing, only to plug it up again.

 

[heyyou325]

I took the pisser clear off and cleaned it good. With the tube unhooked from the pee hole, there is still no water. Yes the pump is working. It fills up the exhaust housing. The fact that the engine if anything was running too cool coming back tells me the pump works, and maybe the thermostat is stuck open. But then I should have water coming thru the bypass(?) and out the pee hole. If I'm remembering how that works right. Also it could be a problem with the water tube as I can't see it past the bend, but it isn't really loose, and I don't want to pull on it as they are hard to reinstall. I have no idea if the exhaust housing has ever been off, and I've never taken them off any outboard. I hate drilling out bolts, and as rusty as some of them look, I know I will be if I try to take it off. I'm just at a loss for what to try next. I've done very little to this motor since I got it 8 or 9 + or - years ago.

 

[Chinewalker]

Can you blow back through the pisser tube?

 

[heyyou325]

Yes, it comes out the water pickup tube, and I don't hear it coming out any other place. I'm not sure how much pressure I can use without doing harm, but I'm using 30 or 40 psi of air, and less than 40gpm, that's all I got, of water. I can fill the pisser tube with water, and it blows right back down the pickup water tube also. I didn't see any leaks going backwards with water either.

 

[F_R]

You know the water is circulating through the powerhead's cooling system. If it wasn't, you would have burned it up in a few minutes, not 20. Therefor there must be something obstructing that tell-tale. BTW, the water "sees" the tell-tale before going on to the rest of the cooling system. In other words, the tell-tale is an intentional leak right up front in the system. So, since you know it is circulating thru the rest of the system, it has to be present in the tell-tale area, just not "leaking" out..

 

[heyyou325]

I agree, but it is also a safety feature so I don't burn up another motor. I blew the sparkplug out of the 69 40 hp I had just before this one and it started the motor on fire, in the middle of a lake. Got the fire out, but it took me a long time to paddle back to the dock, 2 ten year old boys weren't much help then either. If I could get the pisser tube off where it comes out of what I believe to be the exhaust, but the motor back together and started it with a flusher, would that tell me anything?

 

[heyyou325]

Well, I've got everything back together, and I'm still wondering about the thermostat. It takes a full 2 minutes + for the water to start coming out the pee hole. Motor feels cool the whole time. Then after the water starts at the pee hole, it quickly warms up to can't keep my hand on top cylinder, which is normal. Bottom one is not nearly as warm after a full 5 minutes. Guess I'll run it this way for awhile and see where it gets me. Fishing hole is only 12 miles across the lake. Bot will do 21mph with a gps, WOT the way it's set up, that's only about 30 minutes to cross. Thanks for the assistance.