1987 Johnson 50HP cooling route

[dduval107]

I have a 1987 Johnson 50HP that i purchased beginning of the year. There are a few problems with it, but it runs great for about 30 minutes, then wont start. After waiting 30-40 minutes it will start and run fine again until the same issues repeats. Overheat buzzer was inoperable when i bought it, but checked continuity of the sensor after running on muffs for 20 minutes and the switch was closed, which should signal the buzzer.. at rest and not running the temp switch is open. My question. does anyone else's water path look like the one in my video? I feel like something is not right.. Sorry its upside down, not sure how to fix this.
View attachment Cooling Flow Video 2.mp4

 

[Crosbyman]

have you considered changing impeller maybe thermostat before heading into other issues ?

 

[racerone]

If the overheat buzzer was disconnected it may indicate issues.----Next step would be a compression test.-----Post your numbers.

 

[dduval107]

Engine disassembled waiting for water jackets gaskets and new thermostat. Compression was 150psi and 145psi when I purchased it two months ago. Sounded like the engine has same issues before I bought it so I don’t believe those have changed much.

 

[dduval107]

Engine disassembled waiting for water jackets gaskets and new thermostat. Compression was 150psi and 145psi when I purchased it two months ago. Sounded like the engine has same issues before I bought it so I don’t believe those have changed much.

Also thermostat didn’t look great but still functioned when I placed it in hot water..

 

[dduval107]

I was able to reassemble enough for compression test. 150psi both cylinders.

To give more information I changed impeller assembly today, old one looked in decent shape, but still replaced it. Old one created enough pressure to get good indicator stream, as you can see in the video.

My largest concern that most friends have said is why is the water exiting from someplace behind the lower engine mount. Is that where water exits before the thermostat opens up to relieve pressure? I thought it all dumped into the exhaust and out the propeller

 

[dduval107]

View attachment img-1676_im7cMb1J.mp4
I think this video came in better than the original.

I mentioned the buzzer was not operational. it was not unplugged by anyone, I pulled it out and tested with 12v across the two leads and it made no noise.

 

[tphoyt]

You may have some blockage within the water passages. You might be able to track it down to a general area with an inferred temp gun. But at the end of the day you would be better off pulling the head and cleaning out the passages. Was this a salt water motor?

 

[dduval107]

You may have some blockage within the water passages. You might be able to track it down to a general area with an inferred temp gun. But at the end of the day you would be better off pulling the head and cleaning out the passages. Was this a salt water motor?

I picked it up from central Georgia, but it was originally from South Carolina. It doesn't seem to be heavily salted anywhere. The water passage on the head cover were very clean, little to no salt at.


My concern was that the water tube grommet where water comes into the head is leaking. Manual appears to say i'll need to remove the power head and lower unit just to get to that mid section out and replace that grommet. Ill take a look at the other water jacket on the side before i take off the head.

 

[dduval107]

Jackets look to be in near perfect condition. I did stick a hose down the hole where water exits from the engine after flushing through and the water drains out where it did in the video i posted. So this gives me peace that the incoming water tube is hooked up correctly, routing through the engine and leaving the engine properly.


On the tear down of the engine i did notice the impulse line going out to the VRO/Fuel Pump/spark arrestor had a major leak in it, I replaced the lines and will have to confirm proper function after i get parts and reassemble everything. This could explain the running great for a period of time, then losing power and struggling to start for 30 minutes and starting up fine after cool down.

This brings me to my original question: Is the water supposed to drain from there? I never confirmed the engine actually overheated during operation, just concerned that something may not be right with water exiting just in front of the midsection/lower unit joint.

 

[tphoyt]

I have watched your video 10 times now and I’m still not sure what to say.
Although it is normal for some water to flow from that area it does seem to be a bit excessive in my option.
Hopefully someone else will chime in and help you out. Sorry I couldn’t be of more help.
Best

 

[dduval107]

Thanks, I am just going to run with it. I replaced the faulty temp warning horn AND placed an adhesive non-reversible Temperature label on my head. That should give me a little peace of mine if the temp rises above dangerous levels and the alarm sensor doesn't work.


Pretty sure i solved the engine not running properly after 30 minutes. For clarity it would run when i advanced the throttle for warm up, then when i return to normal idle it would die out. Only after the engine warmed up. Turns out the Impulse line driving the fuel pump was leaking just enough to starve the engine of fuel. if I had pumped my bulb I probably would've got it running immediately.

 

[Roadking57]

Thanks, I am just going to run with it. I replaced the faulty temp warning horn AND placed an adhesive non-reversible Temperature label on my head. That should give me a little peace of mine if the temp rises above dangerous levels and the alarm sensor doesn't work.
View attachment 359637

Pretty sure i solved the engine not running properly after 30 minutes. For clarity it would run when i advanced the throttle for warm up, then when i return to normal idle it would die out. Only after the engine warmed up. Turns out the Impulse line driving the fuel pump was leaking just enough to starve the engine of fuel. if I had pumped my bulb I probably would've got it running immediately.

Yeah but didja mount a mirror in the boat to check your skull temp?