johnson 15 horse water exit?

[doc1976]

I was wondering about a PO removing the t stat because it was not getting warm at all plus a little rough at idle to suggest not getting up to temp. I am used to a much bigger motor and when you hook the hose up you get water out the prop and other relief areas in a hurry and with some noticeable flow. may just be expecting too much from this little guy. I plan to get a no contact thermometer and run in a tank in the next couple days to get a more accurate idea of what is happening. If it doesn't warm up or gets too hot then I will know better where to go next. thanks everyone for all the help its greatly appreciated. will post results soon

 

[Pappy]

Thermostat is needed for three reasons.
First reason is for a good smooth idle (compared to no thermo).
Second reason is to keep from making water inside the engine while in colder water.
Third reason is premature wear of the pistons. Hot piston/cold sleeve equals an increased rate of wear.
The information listed in another post is the old wives tale stuff left over from a bygone era.

 

[wmk0002]

The small hole is simply a drain hole for the entire leg for when you trailer the boat to keep from having any freeze in there.

The series of holes above the anti-ventilation plate are exhaust gas holes, however, cooling water also exits there too when you are running it on muffs. It is warm because it has passed through the thermostat and powerhead where as the pee hole that comes out the side is tapped into the the cooling water prior to the thermostat . Same happens through the prop as well as the exhaust port on the upper rear of the leg just under the cowling in terms of outputting warm water with the exhaust.

well I have something not quite right then. I have only a tiny bit of water coming out of the holes above the anti-ventilation plate, no water from the prop or the exhaust port, a good stream from the pee hole, and a stream with enough pressure to shoot 2 or 3 feet from the drain hole. this is the case when the muffs are on, cant figure out a way to see where water is exiting if i run it in a tub.

FWIW, you may actually not see water out of the exhaust hole on the leg. I have a 1982 9.9hp and 15hp and the 9.9 will spray water from that port when the thermostat opens, however, the 15hp won't. This is because the 15hp has a longer exhaust water tube coming out of the powerhead than the 9.9 does for whatever reason....long enough that it extends past the opening. Now, I'm not sure if all 15hp ones are like this or maybe a previous owner used the wrong part or what but wanted to mention it anyways.

 

[Pappy]

Take a look at parts diagrams again.....
The 9.9 has a full length exhaust tube. The 15hp for most of the model years has a short exhaust tuner.

 

[wmk0002]

Take a look at parts diagrams again.....
The 9.9 has a full length exhaust tube. The 15hp for most of the model years has a short exhaust tuner.

I was just referring to the outlet water tube.

 

[Sinkingfast]

The 9.9 had a wet leg...the mid fills with water and spills over the passage inside the rear of the mid. No hole in water tube from pump. Tuned length exhaust.
The 15 used what I call a folded horn exhaust like on my 550sx standup ski. The mid does not fill up with water. Most dumps down the rear passage with a short tube. Has hole in water tube from pump to cool the mid. Tuned to a narrow rpm range since there is no reverse cone, just a target piece at the end of the megaphone.

 

[doc1976]

okay so I got the motor running in a drum today used a 55 gal drum so it would hold plenty of water and not let the water warm up much. ran the motor for 40 minutes mostly at idle with a few revs here and there. the hottest the head got at the top was 99.5 degrees. the head by the plugs saw 104, the water cover over the t stat got to 98, and the side of the crankcase right at the seam got to 106. So i am led to believe either the thermostat is stuck in the open position or there is no thermostat at all.

on a side note, the exhaust relief hole under the cowl latch was spitting out water and exhaust just like the ones in the videos so I guess the motor is pumping water fine.

 

[doc1976]

thanks everyone for your help and suggestions.

 

[CMOS]

Pappy says, "why not just go and run it and check?"


Gotta love words of wisdom from an expert. :mrgreen:


CMOS

 

[doc1976]

so to follow up with this post, if anyone cares or can learn from it, I got the motor repaired. The issue with the motor not warming up was due to the spring that holds the T-stat in place being extremely weak. It did not appear to be holding the stat down so water was getting past without it opening. plus the stat was opening way too early. Also found the wrong grommet was used for the water tube at the pump, as well as the exit water tube being the wrong part, someone replaced it with a pre-85 part. the head came off and was cleaned and surfaced, as was the water cover. replaced seals and o ring on the lower crankshaft head, as well as all gaskets and seals that were removed. Got it running in the tub the other day, and it warmed right up to temp and maintained temp just like it should. so It seems as though all is well with it and as soon as my transom is finished, I can get it out and see how she runs. thanks again for all the help.

 

[CMOS]

Thanks for the update.


CMOS