1974 115HP Johnson Overheat/Water Flow Problems

[kshelly]

I installed a temp gauge on my 1974 115HP Johnson today. Tested the engine with muffs, watched my temp gauge increase to the high side, and set the overheat warning horn off. Engine was HOT! Looks like I'm not getting any water circulation. I removed what I think is the thermostat housing (located at the bottom of the exhaust case between the cylinder heads). The housing has two hoses connected to it, one from each cylinder head. When I pulled the housing, two springs popped out. There's also a plastic saucer-shaped plug and a tiny plastic impeller looking thing. While all these gizmo's were removed, I ran the engine. Still no water flow. I suspect it's time to do the water pump, although when I bought the boat the previous owner told me it was about 1 year old. I also can't figure out how all those "giozmo's" I removed (springs, plug, impeller)are suppose to work, or even how they go back together. My Clymer manual in useless. Any Johnson wizards out there who can shed light on the subject?!?

 

[ledgefinder]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

If you've got no flow with the thermostat box opened up, then sounds like the pipes down to your pump are disconnected/blocked, pump key sheared, or possibly your pump is somehow clogged. Usually when on the muffs, your household water pressure will drive water through the motor as long as the pump is rotating. You'll need to pull the lower unit to see what's going on.

 

[Solittle]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

Your homework is here:<br /><br /> http://www.theoutboardwizard.bizhosting.com/parts_service_and_owners_manuals.html

 

[kshelly]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

Thanks, as usual, for the input. I called the previous owner, who in turn called his mechanic. His mechanic seems to think there might not be a problem. He suggested putting the boat in the water and give it some power. I called my marina to set up an appointment to get my engine looked at, and the mechanic there said the same thing. He wants me to run it in the river first and pull some power. I guess I'll keep my fingers crossed and hope for the best...

 

[DJ]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

erau85,<br /><br />Don't run that engine under power until you figure out what is going on. Or, you'll get to rebuild the whole thing.

 

[ledgefinder]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

Wow - don't run it for more than a few seconds at idle until you get this staightened out! <br /><br />Your pump isn't working, or the pipes to the powerhead are not connected or are clogged. <br /><br />The cooling systems on those V4s is set up so that the pump is piped directly to the powerhead. When the thermostat is closed, a pressure regulating valve opens, and recirculates the water back to down to the water pump (that's why there are two pipes going to your pump). When the thermostat opens, it spills water into the exhaust housing (midsection of the motor). This loss of fluid causes the pressure to drop slightly in the powerhead, closing the pressure relief valve, and making the water pump input just fresh water (no recirculated water). <br /><br />That's the way it's supposed to work. There are two hoses connecting the heads to the thermostat housing, one for each head. If you pull those hoses off, you lower the pressure in the powerhead, closing the pressure relief valve. Therefore all the water coming up from the pump is fresh, cold water (again, no recirculation). This is a cheap, easy test then of the thermostats & pump; if you pull the hoses and the motor cools right off, the thermostat is stuck closed. If the motor doesn't cool off, the pump isn't working, or the piping up from the pump isn't connected, or is clogged.<br /><br />Since you've said you pulled the thermostat housing apart & the motor didn't cool off, I assume your pump is dead. I am assuming you didn't see a good, fat stream of water coming out of the headpipes, right. DON'T run the motor more than a few seconds until you get this straightened out. Pull the lower unit & see what's going on with that pump & piping. <br /><br />The thermostat should be fully open at 130 degrees F, meaning you should be able to rest your fingers on the cylinders for 2-3 seconds (they should be warm/hot, but not burn your fingers). <br /><br />If the mechanic actually suggested running it wide open down the river, in hopes "things would clear up", he or she is nuts.

 

[kshelly]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

I have to admit I'm sceptical too, but I had two different mechanics tell me the same thing. In this case, I hope I DON'T prove them wrong!!!

 

[Solittle]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

There are a great number of qualified professional mechanics out there. Keep in mind though that they make their living by fixing things that don't work. The advice you get here, whether from a pro or driveway wrench, has nothing to do with putting money in anyones pocket.

 

[kshelly]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

SoLittle;<br />I appreciate all the advice I get from this site. I just put down $80 for the Service, Parts & Owner's manual for this engine (which I might need if I blow this thing up!). I'm going to try the advice of my marina mechanic. He suggests leaving the boat on the trailer and back the boat onto the ramp for my run. He swears he's seen this a hundred times. Maybe he has, but maybe that's how he makes his living after people follow his advice and blow up engines, I don't know. I just don't want to go through this aggravation every season after the engine's been winterized just to find out it's normal. I'm going to put my faith in my temp gauge & my warning horn. I'll be standing by with my hand on the key just in case. I'll be taking for it's run in a few hours (if the weather let's me). I'll repost my results.

 

[reeldutch]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

wow,<br /><br />if it was my rig i would drop the lower unit and put a new pump on asap.<br />then if the thermostats are in good shape and it still overheads i would pull the heads and check for waterflow obstructions.<br />running a motor that overheads is asking for big trouble.<br />but if you want to take chances fine,<br />did you ask your mechanic why he wants to run it?<br />he probbebly thinks your tstats are stuck .

 

[kshelly]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

I haven't specifically asked why he wants me to run it. Maybe business is slow! As I said, he claims he's seen this a hundred times before. I'm really "on the fence" with this one. Part of my wants to do as you say and replace the pump, even if just as a precaution. Part of me wants to run the SOB like suggested my the mechs and get a definitive answer as to what's "normal" or not. If I watch the temp gauge, I should be able to shut down before damage is done. And if I hit the lottery, everything will be fine. About 2 hours until I run...

 

[PDS]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

earau85, if it doesn't run right on muffs(water being forced into it) I really doubt it will run right just being dunked in water. My '76 115 with a new waterpump will pump water a foot higher than the engine(wrong waterjacket gasket) When I shut engine off, water stopped comming out of engine. Of coarse if you prove me wrong,all the better for you! Good Luck!

 

[PDS]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

earau85, if it doesn't run right on muffs(water being forced into it) I really doubt it will run right just being dunked in water. My '76 115 with a new waterpump will pump water a foot higher than the engine(wrong waterjacket gasket) When I shut engine off, water stopped comming out of engine. Of coarse if you prove me wrong,all the better for you! Good Luck!

 

[SCO]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

Erau, there is no point in doing a pass fail test if the fail ruins your engine. This isn't rocket science. There is an impeller problem or blockage. MAybe the mechanics think you are not hooking up the muffs right. I think your unit has a vernatherm if it is like my 73 135 jiohnson, and the spring cup stuff. The vernatherm part is what gets frozen and I practically had to use a chisel to get the old vernatherm out of my engine. I bet it is still in there on yours so your testing so far may be invalid. Forget that for now. I discovered from experimentation what Ledgefinder is saying. There is a line that runs directly from the impeller to the heads. If you un hook the two hoses from the tstat housing, and put h2o in from the muff with normal full on water hose pressure, the water will go to the head and drain out the 2 hoses you just disconnected. It is an emergency way to bypass the tstats if you are caught out with tstats that dont open.If it doesnt work with the engine off, then start it and see if it comes out of those hoses. With all the springs/cups/vernatherm out, you should be able also to put water into the tstat housing where you unhooked the two hoses and see water going to the lower unit and draining out at various locations(have muffs off).I also flushed out the heads by putting h2o into the hoses that you need to disconnect for the test. Should go in one, out the other and probably to the lower unit if you block one of the 2 hoses and put water into the other. Good luck

 

[kshelly]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

I appreciate all the feedback I received. Just got back from my dip in the river. What a difference than using the muffs. With the muffs I had zero water pressure on my water pressure gauge, in the river I read 10psi at idle, 24psi opened up. On the muffs my temp gauge climbed high like I was watching the second hand on a clock, in the river the temp gauge stayed well in the low range. I ran full throttle for 10 minutes at least, everything went great! I guess I can consider myself lucky (or at least keep my wallet fat just a little bit longer!). Thanks again to everyone who took the time to reply. I left the boat in my slip and hopfully won't have to pull it out again until November!

 

[SCO]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

You should still be able to run it on the muffs. Did you determine why it wouldn't? Sounds like you wern't getting sufficent water to the intake.

 

[Solittle]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

ATTENTION TO ALL WHO READ THIS THREAD - erau85 took a big risk and saved $60.00 +/-. If he was wrong he would probably be facing a rebuild or replacement of the powerhead as a minimum. I think most who post here on a regular basis would recommend that the waterpump and t-stats be replaced on a new "old" motor reguardless of what the seller or his wrench said.<br /><br />erau85 - Glad it worked out for you.

 

[kshelly]

Re: 1974 115HP Johnson Overheat/Water Flow Problems

In spite of running perfect on the open water, I can't explain why it doesn't take well to the muffs. Maybe my water volume through the hose is too low, I don't know. It'll be an inconvenience not being able to check things out when it's sitting in the driveway, but at least for now the engine runs great. Go figure.