Vapor Lock?

[Jon Boat Jim]

I've witnessed something strange this evening. I replaced the water pump on my 1992 25HP Johnson. Before reinstalling the LU, I made sure that there were no obstructions in the cooling channels by flushing water through the water pipe until it came out the pee outlet. It came out in a strong stream.
I put it in a barrel to test it and it ran fine with a strong pee stream. I let it run at idle for 15 minutes or so to make sure that it wouldn't overheat. Every thing was fine. Then I shut it down, took off the cowl to do a few things and restarted it. To my surprise....NO PEE STREAM.....just exhaust coming from the outlet!! The engine was getting hot to the touch and I shut it down. I flushed water through the pee spout to cool it down and set bewildered for a while and had a beer. I then restart the engine and it had a strong pee stream again. Can anybody offer an explanation?

 

[oldcatamount]

Re: Vapor Lock?

Sounds like a piece of the old impeller is moving around inside the water jacket. Try taking a piece of weed wacker string and working it up inside the pee hole. Sometimes that will dislodge the obstruction. If that doesn't work, remove the thermostat cover and do the same thing with the weed wacker string working it down both ports as far as you can get it.

 

[Jon Boat Jim]

Re: Vapor Lock?

Chief, The old impeller was in one piece and, except for the "set" the vanes, it looked in very good condition. The rubber water pipe grommet was also in one piece with nothing missing.
I've had this intermittent pee stream several times in the last month or so and suspected a blockage. Just a few weeks ago, I replaced the thermostat thinking that the blockage might be there or that it was not functioning correctly. I actually ran the engine for a while without one until the new one came in the mail. The stream seemed strong enough however, the stream and engine became hot after idling. That is when I ordered the water pump kit.

 

[dew2]

Re: Vapor Lock?

when ypou had the L/U off did you make sure the inlet screens were clean? I have a 15 evin.that does the same thing yearly!! found the screens 1/2 cloged with fine cottonwood like seed cotton.Every year!!

 

[Jon Boat Jim]

Re: Vapor Lock?

Chief, this motor has plastic inlet "grid plates" on either side of the LU unit that must be removed to unfasten the shift rod from the LU. They have pretty large openings and were clean.

 

[dew2]

Re: Vapor Lock?

Yah I know.are those openings larger than the tell tale?

 

[Jon Boat Jim]

Re: Vapor Lock?

I'm pretty confident that something could wiggle through the grid and not get through the tell tale.

 

[dew2]

Re: Vapor Lock?

I'm pretty confident that something could wiggle through the grid and not get through the tell tale.

after what you have mentioned in this post,Thats what I would look for next.If the screen isnt smaller than the telltale tube well I guess something could enter and clog it.Strange there's no screen?? I dont know of any weed free lakes.
All parts lists say screened intake.Think you may be missing a screen???

 

[boobie]

Re: Vapor Lock?

How about the water deflectors in the block, blocking off water flow??

 

[Big flop]

Re: Vapor Lock?

After restarting and not pumping, was the water
Still deep enough in the barrel to cover the
impeller housing ?

 

[larryg]

Re: Vapor Lock?

check on marineengines.com and look up motor that u have.think this will tell u if it has a screen there or not.i looked it up but didnt know what model u had.it shows the screen on there for johnson 25.

 

[Jon Boat Jim]

Re: Vapor Lock?

Answers to your questions:
The water level was always well above the impeller housing.
The model # is TJ25ELESE. The schematic shows the plastic grid plates, but no "screen" wire.

Tell me more about the "water deflectors". Can they be seen in the marineengines.com diagrams?

 

[AlTn]

Re: Vapor Lock?

the model no. provided is for a 1990 25 hp....look under the Cylinder and Crankshaft section of the diagrams...#8 and #9 are the deflectors...

 

[Jon Boat Jim]

Re: Vapor Lock?

OK I see them. It looks like that you have to remove the head to access them. Is that correct? Is there some way to poke a weed wacker string through them?

I hoping that when I get this thing out and run it on the Ohio, it will be OK.

 

[AlTn]

Re: Vapor Lock?

yes the head has to come off..which means another head gasket and probably a head cover gasket at the least