77 Johnson 9.9 thermostat

mmcmille · Jun 30, 2007

I've got a 77 Johnson 9.9 that isn't pumping water. I replaced the impeller but it still isn't pumping anything. Someone told me that the thermostat is probably stuck closed. There's not anywhere around here that has a manual and I was trying to get it going for the weekend. I can't seem to find it. I did find a parts page and it looks like it is just below the bottom cylinder but I don't see it. Could someone give me a tip or something? I am planning on getting a manual but I'll have to order one.

thanks

Xcusme · Jun 30, 2007

Re: 77 Johnson 9.9 thermostat

Part # 19 is the thermostat
Part # 20 thermostat gasket

Part # 6 must be removed to replace the thermostat....

mmcmille · Jun 30, 2007

Re: 77 Johnson 9.9 thermostat

oh that's what I didn't see. Pulling part #6 thanks!

mmcmille · Jun 30, 2007

Re: 77 Johnson 9.9 thermostat

well, I pulled it out and started it up. There's no water at all coming out from up there. I blew air through it and bubbles came out of the bottom where it sucks the water in so it's not blocked. There is smoke coming out of the hole where the thermostat was. So, I'm thinking it might be a head gasket. But it starts fine (first pull every time) and I kind of find it hard to believe that there's no water at all getting up to the thermostat. I'm a truck mechanic so maybe it's totally different. I don't know alot about 2 cycle engines.

Xcusme · Jun 30, 2007

Re: 77 Johnson 9.9 thermostat

Hmmm, is it smoke (exhaust) or steam?? You should get water to puke from the thermostat opening. I'd drop the lower unit, fit a water hose to the water pipe and force water up into the power head to confirm clear water passages. Perhaps you missed inserting the water tube into the water pump or perhaps the impeller key slipped out. Just because you can blow air through the cooling system doesn't mean water will pass through efficiently, push water up the tube.

mmcmille · Jun 30, 2007

Re: 77 Johnson 9.9 thermostat

Ok, I'll try that then tomorrow. The smoke is blue and the other day I put my thumb over the hose that the water comes out of and there was a little air coming out of it.

Xcusme · Jun 30, 2007

Re: 77 Johnson 9.9 thermostat

Exhaust from the tell-tale is not a good sign. If that motor was run without a working water pump, you may have blown a head gasket. If the head gasket is blown, it can pressurize the cooling passages, preventing cooling water from the pump to reach the power head. Since you've gone this far, removing the thermostat ,go a bit further and remove the head and inspect the head gasket. This will give you a good look at the pistons and cylinder walls too. Clean out cooling passages as needed while you're in there. Another indication of a blown head gasket are clean piston tops and steam cleaned plug(s).

Take it step by step and report back what you find. You certainly can't run the motor like it is without doing major damage.

mmcmille · Jun 30, 2007

Re: 77 Johnson 9.9 thermostat

Yeah, I ddin't figure that was a very good sign. When I took it out the first time this year I noticed that it wasn't pumping any water so I quit using it right away. The weird thing is that it worked fine last year when I quit using it.

I'll post what I find tomorrow.

mmcmille · Jul 1, 2007

Re: 77 Johnson 9.9 thermostat

I pulled the lower unit off again and blew water through everything and put it back together again and now it works! I pulled the plugs out and they're not really clean so, I don't think it is the head gasked. Not today anyway.

Xcusme · Jul 1, 2007

Re: 77 Johnson 9.9 thermostat

That's good news. Watch the tell tale stream closely and test the head temperature. If you can hold your fingers on the head for a few seconds without getting burned, you should be good to go. Any signs of steam from the tell-tale, it's over heating.

mmcmille · Jul 1, 2007

Re: 77 Johnson 9.9 thermostat

I'll be keeping a close eye on it. thanks for the help.

mmcmille · Jul 1, 2007

Re: 77 Johnson 9.9 thermostat

how hot should they run? Like if I had a IR thermometer.

Solittle · Jul 1, 2007

Re: 77 Johnson 9.9 thermostat

Around 140 degrees - my 75 does not have a tell tale.

mmcmille · Jul 1, 2007

Re: 77 Johnson 9.9 thermostat

is it ok to run those without a thermostat in them?

Xcusme · Jul 1, 2007

Re: 77 Johnson 9.9 thermostat

Nope.....I wouldn't....the thermostat's job is to regulate and maintain the temperature of the power head. Cold power head with hot pistons spells trouble with scored cylinder walls and scuffed piston skirts. Can you say "cold seizing"...(as you might guess...it's not a good thing).

mmcmille · Jul 1, 2007

Re: 77 Johnson 9.9 thermostat

ooook, I'll put it back in then.

77 Johnson 9.9 thermostat

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