2003 115 Johnson Ovewrheat when sounding (Trolling speed)

[Fazz90]

Hello all,

Had an issue with the Motor not starting a few weeks a go after not being used for a few months. Did all (what i assume to be) the small checks: bad fuel, dirty carbs, battery, safety switch on ignition, spark plugs etc, which didn't fix the problem, further research revealed it could be the power pack, so i replaced it. Motor started no problem.

Took it for a day out and did over 40km and she ran like a dream, covered a lot of distance in WOT, a fair bit of sounding (5knts), without a single problem. It actually fixed another problem i had when at higher speed and revs the motor would just choke as if it lost all voltage of all of a sudden, then go back to normal

Took the boat out again over the weekend, everything was going ok, except this time after about 15 mins of sounding (5knts), overheat alarm and light came on. So i flicked back to neutral, and turned the motor off, then switch it back on to Ignition and overheat alarm and light is off, turn it back on and all is fine. Then another 5-10 mins of sounding and the overheat alarm and light is back on, so repeat the 1st procedure again. This happened about 3-4 times only whilst on low revs during sounding.

A good stream from the tell tale is present, and the interesting part is the motor doesn't go into safe mode when alarm does go off.

Motor runs fine when at higher revs and idle.

Earlier this year (March i think) i replaced, water impeller, and replaced both thermostats

Powerpack replaced a couple of weeks ago

I'm thinking it's a faulty sensor?

Any thoughts would be greatly appreciated

[Flex]

Did you feel how warm the water was out the tell-tale when the alarm went off?
See if it's genuinely over heating.
I had an issue where two brand new impellers on my twin outboards both caused overheating at low revs. Telltale was coming out what seemed fine but obviously not quite enough.
Good indication is the motor will overheat after 5-10mins of trolling/idle.

I was lucky and had nmea setup on both motors and could see the temp slowly rise under idle. At cruise speeds then temps were totally fine.


But check your telltale temps first to see if it's real or sensor related.


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[Fazz90]

Thanks Flex.

Will check the tell tale water

Is there a range the water temp should be at?

[Flex]

Should be bath temperature.
If you can't hold your hand under the water it's running hot.
Most sensors are set to 65deg to alarm I think.. but don't quote me.
My yamahas would alarm at 65deg


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