Yamaha 60 HP Two Stroke Overheat Frustrations

[Supercaiber]

Hi All,

Longtime lurker seeking help!

I have a 2002 TLRA 60 HP with very low hours (70) that gets the over heat alarm at low RPM’s after 7-8 minutes regardless of it’s on muffs or in the water. High rpm’s are not an issue and runs well.

I’ve literally tried everything and reluctant to pull the head as I’m afraid to snap bolts (I did buy the gaskets though)

I’ve measured the cylinders with infrared and the top two run ~15-20 degrees hotter than the bottom one

The tell tale flow is decent and cool/warm, then goes straight to scolding hot when the alarm sounds

Additional info & actions taken (all replacement parts are OEM)

- Water pump kit is brand new, including housing (changed twice)
- Thermostat is brand new
- Temp sensor is brand new
- Flushed twice with Salt Away
- This motor doesn’t have a poppet valve

Any thoughts or advice are greatly appreciated.

[brian3006]

I know you said you changed it, But Man that sure sounds like a weak impeller not getting enough pressure to move the water efficiently at idle...
As far as the thermostat..I have learned the hard way that new does not equal good. Take it and test it in a pot of water with a thermometer.

It is normal for the top cylinders to be warmer. that is why the temp warning indicator is at the top of the engone. You said you tested temps with an IR gun. What were they when the alarm goes off??

If everything checks out you might be to the point of having to pop the heads off and manually remove the build-up (if there is any). I am assuming this is a salt water motor???
The salt away is really designed to use as a flush..not to dissolve hard-crusted deposits. There are solutions that are made for this such as barnacle buster and rydlyme. look up on youtube and you can see ways to flush your engine with these.
But with only 70 hrs on it...seems fairly low to have blocked passages..

Last year I had a 90 with this exact issue. It was the impeller... changed it and have not had an alarm since..

[Supercaiber]

I know you said you changed it, But Man that sure sounds like a weak impeller not getting enough pressure to move the water efficiently at idle...
As far as the thermostat..I have learned the hard way that new does not equal good. Take it and test it in a pot of water with a thermometer.

It is normal for the top cylinders to be warmer. that is why the temp warning indicator is at the top of the engone. You said you tested temps with an IR gun. What were they when the alarm goes off??

If everything checks out you might be to the point of having to pop the heads off and manually remove the build-up (if there is any). I am assuming this is a salt water motor???
The salt away is really designed to use as a flush..not to dissolve hard-crusted deposits. There are solutions that are made for this such as barnacle buster and rydlyme. look up on youtube and you can see ways to flush your engine with these.
But with only 70 hrs on it...seems fairly low to have blocked passages..

Last year I had a 90 with this exact issue. It was the impeller... changed it and have not had an alarm since..

Thanks for the thorough response!

I’ve changed the impeller twice. Second time I replaced the impeller and cover that the cup sits in because I noticed some gouges inside of it. Almost like the metal cup spun freely inside. I’ll drop the lower unit and have another look and let you know.

For the thermostat, I’ll test it as well and let you know.

The temps must of been around 170 when the alarm went off. I measured them as they were warming up and I think they were at 165ish. I set the IR gun down, put my hand in the tell tale and the water was still cool. About 15 seconds later the alarm went off and the tell tale turned scolding hot.

it’s a saltwater engine and outside of this issue it runs really well. Compression is low 120’s across all three cylinders.

I’ll be back with updates in the next 1-2 days

Thanks Again!

[Keithbaja]

The cup has a "O" on top and a seal on the bottom.. The complete cup should be sealed to the housing.. Not loose at all. Only a fool would watch a YouTube outboard repair vid.. The blind leading the blind

[TownsendsFJR1300]

. Second time I replaced the impeller and cover that the cup sits in because I noticed some gouges inside of it. Almost like the metal cup spun freely inside.

You may want to change the "housing" the cup sits inside of. Any warpage / damage will cause issues, especially at low RPM's.
As noted, make sure all the o-rings in the housing / at the cup are in place properly. A touch or sealer, on the o-rings help keep them from moving about..

[Supercaiber]

Okay, I had some free time this morning.

I dropped the lower unit to inspect the water pump/impeller and it all seems good to me. See attached pictures. I’ll order another kit and replace to be sure. The water pump cover in the picture was replaced recently, but have a look.

I also pulled the stat and it opened up in boiling water.

what are y’all’s thoughts in the picture of the area behind the thermostat. Does that buildup lead you to believe there’s a fair amount in the head?

Thanks again!

[zenoahphobic]

Okay, I had some free time this morning.

I dropped the lower unit to inspect the water pump/impeller and it all seems good to me. See attached pictures. I’ll order another kit and replace to be sure. The water pump cover in the picture was replaced recently, but have a look.

I also pulled the stat and it opened up in boiling water.

what are y’all’s thoughts in the picture of the area behind the thermostat. Does that buildup lead you to believe there’s a fair amount in the head?

Thanks again!

Build up behind the thermostat looks normal but you can’t tell what the water passages in the head have got in them from this.
Where is the stainless steel cup and plate?

[brian3006]

Agreed.. the water passage behind the T-stat look great. Like zeno siad though, that doesn't mean that there is not any build-up in the heads, but I would think they would be in similar condition...

So as for the T-stat... you said that it open in boiling water... do you know what temp it opened at? That is what you want to look for. It should open at around 140 I believe... (someone please correct me if I am wrong)
and I think the overheating alarm is triggered at 180.

[Supercaiber]

Build up behind the thermostat looks normal but you can’t tell what the water passages in the head have got in them from this.
Where is the stainless steel cup and plate?

Here’s a look at the cup and plate. Any thoughts?

I’m tempted to pull the head, but reluctant because I don’t want to break bolts.

[Supercaiber]

Agreed.. the water passage behind the T-stat look great. Like zeno siad though, that doesn't mean that there is not any build-up in the heads, but I would think they would be in similar condition...

So as for the T-stat... you said that it open in boiling water... do you know what temp it opened at? That is what you want to look for. It should open at around 140 I believe... (someone please correct me if I am wrong)
and I think the overheating alarm is triggered at 180.

Funny, this crossed my mind when I dipped it. I’ll measure the temp tomorrow and see what temp it opens at.

[99yam40]

Yamaha service manual gives the specs for all of this temp stuff.
Starts to open and fully open. even closing spec
temp alarm sounds, etc.

do you have one for your motor?
if the alarm is sounding at a lower temp than it should, then check the switch that sets the alarm to make sur it operates in spec. too

[Supercaiber]

Yamaha service manual gives the specs for all of this temp stuff.
Starts to open and fully open. even closing spec
temp alarm sounds, etc.

do you have one for your motor?
if the alarm is sounding at a lower temp than it should, then check the switch that sets the alarm to make sur it operates in spec. too

When the alarm sounds, the tell tale goes from cool to steaming hot. Any idea what would cause the quick change in temp at the tell tale? No poppet valve on this engine. Also there’s a small amount of steamy water coming out of the exhaust port when the alarm sounds.

For the switch/sensor, I replaced it with a new OEM one.

[99yam40]

none of this means you know they operate in spec until you measure it and prove it.

You have a21 year old motor that has only 70 hours of run time.
that means it has run less that 4 hours a year on average.
letting a motor sit is bad.

there is a chance that you have debris in the cooling passages that get in the way from time to time.

or your pump is sucking air or maybe exhaust some how

[Keithbaja]

Ok,, the basics. At low rpm's the pump must work 100%. Any air leak into the impeller area will do what your described. I use a loctite sealant on the complete SS waterpump "Cup" water is 900 more times dense than air. So even a little leak can cause issue's.. When up and on plane the water is being forced/jammed thru the pump, flexing what is now considered a centrifugal pump... As in at higher speeds you can take out the impeller and run fine..

[Supercaiber]

none of this means you know they operate in spec until you measure it and prove it.

You have a21 year old motor that has only 70 hours of run time.
that means it has run less that 4 hours a year on average.
letting a motor sit is bad.

there is a chance that you have debris in the cooling passages that get in the way from time to time.

or your pump is sucking air or maybe exhaust some how

Thanks! Next step is to measure the thermostat. Just waiting on a new thermometer.

I also have a new thermostat in route that I’ll test in parallel.