1981 johnson 175 hp pressure relief leak

[wickers]

Hello again guys and gals.

Here's my current problem. I replaced the thermostat, thermostat grommet, thermostat cover gasket, pressure relief valve, pressure relief valve spring, seal to valve screw, spring retainer, pressure relief valve seal, valve seat, and valve washer on both cylinder heads. I did this because the motor overheated and melted the old pressure relief valves. I used all new OEM Johnson parts. Now when the motor is running on muffs the thermostat covers leak out the hole in the center of them. The one on the port side just has a small dribble out it but the one on the starboard side has a nice stream out of it. I also replaced the water pump>

What did I do wrong? Do these normally leak when on muffs because of high water pressure from the hose? Since its winter and I'm not a diehard, its too cold to go to the lake and try it there when its not on muffs.

Again as always thanks for your time and knowledge.

 

[Joe Reeves]

Re: 1981 johnson 175 hp pressure relief leak

That's a common problem...... Remove the diaphragm, check the metal sealing surfaces for salt corrosion, metal portions that might have broken away, etc. If the surfaces are okay, clean if needed.

Apply some sort of sealer around the edges of the diaphragm (the approx 1/8" diameter portion of the diaphragm), insert it where it belongs, and install the cover. That should do it.

 

[wickers]

Re: 1981 johnson 175 hp pressure relief leak

That's a common problem...... Remove the diaphragm, check the metal sealing surfaces for salt corrosion, metal portions that might have broken away, etc. If the surfaces are okay, clean if needed.

Apply some sort of sealer around the edges of the diaphragm (the approx 1/8" diameter portion of the diaphragm), insert it where it belongs, and install the cover. That should do it.

I have a can of Johnson's gasket sealing compound, this will work right? Thanks for the help.

 

[Joe Reeves]

Re: 1981 johnson 175 hp pressure relief leak

I have always used the following (Bombardier 3M Product #847) but what you have is worth a try.

Marprox Sealer 1000 or OMC Adhesive or Boat Armor Sealer 1000 (same substance)[See Below Note] should be used on any metal to metal (Unless GelSeal Is Called For) or metal to plastic surface (such as impeller hsg to plate, and plate to lower unit surface) to eliminate air leaks. It should also be used on the Spaghetti tubing that is used on many powerhead crankcase halves, lower unit skegs, etc. I have found that this substance works quite well on various "O" Rings such as what are found on lower unit carrier and upper driveshaft bearing housings (Note that this substance is obviously not to be used on all "O" Rings). This substance also works quite well in sealing the surfaces between the lower unit and the exhaust housing to which it attaches, eliminating the unsightly water spray between the two after completing a water pump installation.

NOTE 1: I am under the impression that Marprox Sealer 1000 and Boat Armor Sealer 1000 is no longer available.

NOTE 2: OMC Adhesive is now Bombardier 3M Product #847 .