Johnson 115 Outboard overheating

[Fazz90]

G'day all,

Relatively new to the forum, 1st time poster.

I've got a 5.3m Cuddy, Freedom Escape, with a 2003 115 2 stroke Johnson on the back.

On the last couple of trips the temp alarms have gone off as we're leaving the ramp (low idle), and on the way back (also low idle).

When when at higher rev ranges no problems occur. Back at home when flushing with freshwater, i notice the tell tale water is quite warm, exact temp not know, however temp increases once i turn the motor off and the last bits of water trickle through the valves.

I'm thinking Water pump/impeller wouldn't be the cause as there is quite a steady stream of water flowing the telltale.

Am i wrong in thinking it may be the Thermostats? Which regulate water temp pumped in cylinder heads and walls.

Any advice is much appreciated.

[Noelm]

Could be the water pump, or the thermostats, or both..or a blockage in the cooling system , or lots of other things.

[Chimo]

Fazz

Is the overheating on one side of the vee or both sides? When it gets hot and the alarm goes off and the speed limiter cuts in pull the cover off and with your hand test the temps on both of the heads.

My guess its only one side that is really hot

Anyhow pull both thermostats out and measure the size of the hole in the rubber that the thermostats are pushed against by the springs. You can just use a finger to gauge the hole sizes.

Fifteen years after I diagnosed the same issue in one of my 115HP Evinrudes.

BRP have recently released a reworked spring with less tension to allow the thermostats to move back and forth more easily to enhance cooling

Back to the hole size. If one is smaller and as a result the thermostat sits further back and thus has more spring pressure on it you need to remedy this. There are two ways .

Firstly fit new rubbers

or

quick and easy way bore the size out on the small hole rubber with a bell shaped stone on the end of your drill. Enlarge it so they are both the same size.

Note the good hole has dimmples so the thermostat does not jam. Make the equivalent reverse "dimples" with a small trianglar file ie cut a number of grooves that water can flow through and allow the thermostat to move back as the water flow increases.

Also buy some of the shorter springs, and fit to both sides

Or; strip some of the stainless steel band out of an old windscreen wiper blade and use the ss to wrap two coils of the thermostat spring together to make a slightly shorter spring.
A couple of ss ties on each spring and you get enhanced cooling and no more overheating/

As I said I fixed my overheat issue about 15 years ago and all is still good. Another ten years or so and my 115HP Evinrudes will be run in, great motors by the way.

You also need to ensure your water pump impeller and its housing is up to spec.

Finally you can buy scoop water inlet covers to fit on your leg and these add to the water flow entering the motor which wont hurt either.

Have fun

Cheers
Chimo

[Fazz90]

Thanks on the info Chimo.

I did notice that the cylinder heads on the RHS were hot, however, i didn't end up having a feel on the other side.

Would the thermostats be located at the back of the motor near the tell tale on my Johnson?

[Chimo]

You caan find pics here

https://www.google.com.au/search?q=exploded+view+of+2000+115HP+Evinrude&ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&ei=m4OiWN6ZOtHN8geQ0ofAAQ

[Fazz90]

Thanks mate, appreciate your help

[Dirtyfuzz]

If i might add, just had the same issue with a 1990 v4 115, hot on one side , i removed the rubber pipes from bottom of head to thermostats and the hot side had less flow, rigged up a tool to flush head with high pressure water then ran motor in a wheelie bin full of water to clear any gunk and the problem was fixed

[Chimo]

Great motors aren't they!

Did you check to see the size of the holes in the rubber that the thermostats fit into ?

[Fed]

Overheating at idle will be the water pump, overheating at speed will be a blockage or a Chimo/thermo problem.
If you have a blockage or a Chimo/thermo problem I can guarantee it would sound the alarm at speed.

[Chimo]

Fed

You are correct.
My issue from years ago was most evident when I cranked both motors up on the Nerang in flat water and ran at about 40kn for a while.
The overheat alarm would go off on one motor and the motor would reduce speed to keep it safe.
Feeling the heads at that point highlighted that one side was hot and the other not so.

From then on the hunt was on to find and come up with a fix. It was all to do with the size of hole in the rubber that the thermostat interfaces with and the spring pressure applied to the thermostat. They recently began supplying a reduced pressure spring would you believe; only 15 yrs after I fixed mine!

I also fitted cup water intakes to the legs so I may need to take them off if I move to the Antarctic. Otherwise all good.

Cheers
Chimo

[Spaniard_King]

Overheating at idle will be the water pump, overheating at speed will be a blockage or a Chimo/thermo problem.
If you have a blockage or a Chimo/thermo problem I can guarantee it would sound the alarm at speed.

I agree with Fed, I find engines that overheat at idle its a temperature control issue. engines that overheat at RPM then its usually a flow issue.

I would also do what Chimo has suggested as it will be an issue sooner or later

[Fazz90]

Ended up changing, the whole water pump kit, exhaust seals, and thermostats.

Pain in the a@#$ aligning the shift rod into the mechanism on the power head of the engine.

No more over heating problems. However, i've noticed of late, that the engine sometimes stalls when at idle.

for example, after turning it on at the ramp, its fine idling and warming up there, and then taking off hitting crusing speed all good. But then after a few starts and stops moving around to fishing spots, the engine stalls after being turned on.

it does this a couple of times, then once in gear, it goes ok.

Could this be a Carburetor problem or an electrical problem?

[Chimo]

Did you check the size of the holes in the rubber under the thermostats?

Did you check the old thermostats themselves, ie in water on the stove being heated to see the temperature the actual thermostat opens?

The issue I described above was not the fault of the actual thermostats.

[Fazz90]

I did Chimo.

However, i didn't notice any difference. To be honest, i didn't really have a lot of time to be stuffing around with altering and modifying parts. With doing long hours at work including Saturdays, having a baby at home, my free time is scarce at the moment. Hence, why i just ordered the whole water pump kit and 2 new thermostats, and just changed everything for piece of mind.

In saying that understand by doing that, i didn't really find out where the problems stemmed.

I do appreciate your input on the issue though.

Would you have any thoughts on the motor just shutting down at idle?

[Chimo]

The fuel pump has a diaphragm to pump fuel and there is a spring attached to both sides of it.

I had an issue with both my motors within ten hours of each other of the motors cutting out.

Was a bugger to work out the cause on the first instance but 5 minutes the second time.

Check that both springs are attached to the diaphram.

If one lets go the motor wont run for long. After some time it will but them it stops.
Repeat over and over.

Not sure if this is your issue or not but easy to check.

Good luck.

Chimo