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SUBJECT: # 15140: Johnson 15hp water pump?

Submitted by Roger. ( from SOUTH CAROLINA on 5/5/2000 9:31:00 AM

Just got a 1975 Johnson 15hp(15r75c) that has not been used for several years. I put a kit in the carb,cked compression..OK, replaced the impeller, changed foot oil(looked good)and had fire at the plugs. The motor cranked up and ran great, but did not pump water. I let it run for about two minutes and and still no water out of the hole directly under the latch for the cowling. Do I have a bad thermostat or possible just impatient. I will be pulling the foot off again after work to check the water pump. But just wanted some advice from you guys. The little motor ran so good I did not want to damage it by overheating. Thanks Roger

  1. 5/5/2000 10:56:00 AM Submitted by Phytoplanktpon ( from CALIFORNIA says Don't be too hasty
    Roger, disconnect the rubber water line that comes out of the block and feeds the tell tale, then snake a piece of thin wire up the hole into the block, then down the rubber hose. There is probably a little dirt or rust particles blocking the outflow. Unless you did something grievously wrong when putting the impeller in (did you remember to replace the round key that slips between the impeller and the drive shaft?) the water pump is probably working but the tell tale is plugged. If that doesn't work pull the thermostat, start it, and see if it's pumping water, I think I'd replace the Tstat on that engine just for good measure.
  2. 5/5/2000 2:22:00 PM Submitted by Dunk ( from NEW JERSEY says Pisser?
    I don't think that 75' has a pisser. Directly under the latch would be the main above water exhaust. It would still be tstat problem. 2 mins at idle may not be enough time to heat the thermostat to open. Plus it could be sticking. The Tstat should be in the tower that sticks up above the upper piston with 3 bolts holding the cap on. I'd pull that cap then start it. You should have water flying almost right away if the impeller was installed right like Phyto says with the key in place and the water tubes hooked up above the pump. At this point you might as well replace the tstat. You can run without it till you get one if you have too, but you should put one back in there.

    I'm having a hard remembering what A 75' looks like. I keep picturing the older 18's that were made till 65. It was 74 when they came out with the newer style 15's so maybe it does have a pisser. If this is case do what Phyto says about cleaning the pisser hose. In fact pull the hose right off the engine then start it. You should have a stream of water at the fitting and you'll know where the block is. Dunk

  3. 5/5/2000 3:27:00 PM Submitted by Phytoplankton ( from CALIFORNIA says Pisser?
    Dunk, come to think of it your right, I have an 89 evinrude 15 hp. that has a pisser, I also have a 74 9.9 that doesn't. The 9.9 and the 15 are the same block, and usually Rude and Johnson are pretty much the same.
  4. 5/5/2000 6:07:00 PM Submitted by Dunk ( from NEW JERSEY says Pissers and Flush Ports.
    Most are under the misconseption that pissers and flush ports are something only on the new engines. My 49' Evinrude 50hp Big Four has two, one on each side of the engine under the cylinders right through the water jackets. They also act as drains when the engine is shut off. I have 53 25hp rude with a flush port on the leg. My brothers 58 Mark 28a 22hp Merc has flush port. My 60 35hp Merc has a flush port.

    Seems they got away from pissers and flush ports thru the 60's and most of the 70's. Then all of a sudden their back, it's like they wanted you to believe they just invented these old ideas. Dunk

  5. 5/5/2000 6:26:00 PM Submitted by rude dude ( from TEXAS says 75-J-rude
    the 75 15 thermostat is at the bottom of the head almost where the latch is,,,,,,7 or 8 ,, 7/16 headed bolts hold the cover on,,,,,i would run it a little longer before pulling the therm. ,,,,it takes a little while to open up,,,,,,safe boating,,,the rude dude,,,
  6. 5/5/2000 11:00:00 PM Submitted by Roger ( from SOUTH CAROLINA says Thanks
    Thanks guys. It was the thermostat, I pulled the cover and it was gunked up pretty bad and stuck shut. Broke two of the six bolts that hold the cover on. But was able to get the bolts out and salvage the threads. Roger
  7. 5/6/2000 3:50:00 PM Submitted by Water Hole ( from FLORIDA says 15 HP Johnson
    My 9.9 HP Johnson had an overheating problem that turned out to be a damaged gommet (caused by corrosion) where the copper water tube from the water pump entered the head. It had restricted, but not completely stopped, the water flowing out of the pee opening. An OMC mechanic said this was a problem with those engines. I believe your 15 HP is basically the same engine. Just something else to consider while trouble shooting your engine. Good luck.

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