bizzyb

Yamaha 60hp 2stroke overheat at idle

49 posts in this topic

3 hours ago, Flickn Mad said:

Ha ha the site says im a Morwong, they cant even spell mooron wight.

Be careful throwing stones when you didn't spell right correctly yourself.lol.

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fished for years outside   never caught a moron...sorry if I misspelt it

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On 13/10/2017 at 3:14 PM, Hateanchors said:

Some of the reasons the barrel flush is better. 

That’s right, the thermostat opens very little. You can flush for hours and still won’t remove all the salt as there is very little water flow going through the galleries. It’s inevitable that salt will build up inside over time. 

Interested about this theory.   Does anyone know what temperature the thermostat opens at and/or opens fully at?  When I googled my thermostat it just said it was a "Mercury 60'C (140'F) thermostat".  Assuming that means fully open?

 

When I flush with muffs I usually go 5-10 mins.  The water coming out the telltale is warm but def not 60C.  60C is like a hot coffee.

 

Might invest in a barrel, I hope the insides of my motor dont look anything like Flickn Mad's!!!

 

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2 hours ago, Fishop said:

Interested about this theory.   Does anyone know what temperature the thermostat opens at and/or opens fully at?  When I googled my thermostat it just said it was a "Mercury 60'C (140'F) thermostat".  Assuming that means fully open?

 

When I flush with muffs I usually go 5-10 mins.  The water coming out the telltale is warm but def not 60C.  60C is like a hot coffee.

 

Might invest in a barrel, I hope the insides of my motor dont look anything like Flickn Mad's!!!

 

The temperature stamped on any thermostat is the temperature where it will begin to open.Iv,e never seen a telltale on any engine come out like hot coffee with a good working thermostat installed.My yamaha you can run all day and the telltale temp barely changes. 

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1 hour ago, Fab1 said:

The temperature stamped on any thermostat is the temperature where it will begin to open.Iv,e never seen a telltale on any engine come out like hot coffee with a good working thermostat installed.My yamaha you can run all day and the telltale temp barely changes. 

So how can you tell when your thermostat is fully opened?

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43 minutes ago, Fishop said:

So how can you tell when your thermostat is fully opened?

You can’t tell. It usually never fully opens. It only opens enough to let just the right amount of water through to keep the engine at the correct temperature. If the engine needs to be cooler it will open more. 

Things that will cause it to open more are warmer water going in, the engine working harder, higher revs or anything that would make the engine temperature rise. 

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4 hours ago, Fishop said:

So how can you tell when your thermostat is fully opened?

Thermostats have two temperatures that are important.The opening temperature which is stamped on it,and the fully opened temperature found in the workshop manual for the engine.

  Bench testing it is really the only way to test it properly.It involves removing the thermostat from the engine and suspending it in a cold pot of water without letting it touch the sides or bottom of the pot.You then place a thermometer in the water and slowly bring the water to the boil noting that the thermostat begins to open at the specifications in the book (60deg) and is fully opened at ?deg in the book.If it opens at a different temperature outside these parameters it fails.If it fails to open at any temperature or fails to open fully,it fails.If it opens fully and then fails to close as it cools it fails.

  The best thing to do is replace it with a new one and then you can be assured you've eliminated any doubt with the thermostat.

 

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i didnt think of that. You could find out what temperature the thermostat fully opens at, then test the engine temperature. But it usually won’t fully open. 

For flushing, I warm the engine a bit at idle then I keep the revs up to about 3000rpm until the water comes out warm for a few minutes and that’s it. Whole thing takes about 15mins. 

Another reason to use a barrel. It’s  quiet so you can put the revs up if you want. 

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if you use a barrel any saltwater or salt goes into barrel then your washing your motor out with a weak saline solution that gets stronger if you don't change the water...rick

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1 hour ago, rickmarlin62 said:

if you use a barrel any saltwater or salt goes into barrel then your washing your motor out with a weak saline solution that gets stronger if you don't change the water...rick

The amount of salt contamination is very small and makes no noticeable difference to cleaning. I wouldn’t use the same water more than once though. 

I use a round plastic garbage bin. You still need the hose in there on slow to keep it topped up as the engine vibrates or whatever and some water splashes out, so the water slowly gets renewed as well. Also, my teltale doesn’t go into the barrel. 

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Cool, thanks for that.  Might give it a try next time I go out, see if my water turns dirty if I use some vinegar.

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The telltale will always run cold if cold water is going in. Desn't most of the cooling water get expelled via the exhaust and through the prop? That water should be warmer.

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3 hours ago, TheFoosh said:

The telltale will always run cold if cold water is going in. Desn't most of the cooling water get expelled via the exhaust and through the prop? That water should be warmer.

Yeah, most of the water does go through the prop, but on my Suzuki 60 both the telltale and prop water get warm evenly during flushing. Even with cold water going in. (On muffs)

Does anyone know if the telltale water does go through the engine when the thermostat is open?

Edited by Hateanchors

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4 hours ago, TheFoosh said:

The telltale will always run cold if cold water is going in. Desn't most of the cooling water get expelled via the exhaust and through the prop? That water should be warmer.

Edited my response to add more clarity as last response was bashed out on iphone screen and may have been abrupt:

The telltale does not always run cold on my 200hp merc or 15hp mariner. Telltale water is cold at start and goes warm/hot. My mechanic told me that it goes warm when the thermostats have opened. I flush for 10+ min after telltale goes warm.   I use muffs + my silencer gizmo and fresh water input.

Most things in chemistry are driven by a gradient. Ie. The bigger the difference between the materials the faster they combine to reach equilibrium. So as you flush there is less and less salt in the motor. To get as much of that last bit of salt out you need as fresh water as possible. In the ideal world we’d be flushing with demineralized water - as that water has no soluble loading at all. 

If someone buys me a few beers I’ll go back to my Chem Eng textbooks and dig up the salt (NaCl) in water solubility curves at various temperatures. 

The underlying principles are that water can only carry so much dissolved salt before it reaches a saturation point at which it will not be able to absorb any more salt. As you approach that saturation point it will take longer and longer to dissolve salt as there is less gradient (difference) driving it.  Heat will help reach the saturation point sooner.

So if you are flushing with a bucket - the results will be better if its a big bucket - the more water - the more salt you can dissolve - the more dilute the water is the bigger the gradient to get the last salt dissolved  etc.

Or alternatively, do a bucket flush...then finish off with a short run on muffs and clean water.

Cheers 

Zoran

Edited by zmk1962
clarity

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On 13/10/2017 at 4:16 PM, Hateanchors said:

Any Yamaha dealer. 

So we got round to installing the new thermostat yesterday and got most of the way through the impeller repair but found this little problem.. someone glued the impeller cover to the housing!!

I didn't order a replacement housing but have picked one up today. The impeller wasnt actually in too bad of a condition but obviously the previous owner had some issues and though a bit of construction adhesive would do the trick. 

 

Hopefully with the stat change and a new housing the O/heating will be resolved. 

P.s. the Yamaha dealer advised against taking the head off, except as a last resort. 

 

 

On 12/10/2017 at 1:27 PM, Hateanchors said:

As I said earlier, the only way is to take the head apart and manually clean it. 

On 12/10/2017 at 1:27 PM, Hateanchors said:

 

IMG_20171022_164205.jpg

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1 hour ago, bizzyb said:

 

P.s. the Yamaha dealer advised against taking the head off, except as a last resort. 

 

 

IMG_20171022_164205.jpg

Last resort? How else do they suggest to clean the junk out the water passages then?

 

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Opening up a motor is always a desperation move unless absolutely warranted. I agree with your dealer.

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43 minutes ago, TheFoosh said:

Opening up a motor is always a desperation move unless absolutely warranted. I agree with your dealer.

I disagree. We are talking about a 2 stroke engine. Taking the top cover off the head and cleaning out the water passages is a simple thing.  I done the same on my old 60HP Yamaha and it needed it badly. I’m guessing this engine does as well. Look at the condition of the thermostat housing. You can bet the water passages are clogged up similar. 

Ive spoken to other mechanics and they say it should be done as part of periodic maintenance on these particular engines. 

Edited by Hateanchors
Spelling.

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On 23/10/2017 at 8:21 PM, Hateanchors said:

 

I disagree. We are talking about a 2 stroke engine. Taking the top cover off the head and cleaning out the water passages is a simple thing.  I done the same on my old 60HP Yamaha and it needed it badly. I’m guessing this engine does as well. Look at the condition of the thermostat housing. You can bet the water passages are clogged up similar. 

Ive spoken to other mechanics and they say it should be done as part of periodic maintenance on these particular engines. 

Replacing the impellor housing made a massive difference in the strength of the tell-tale so hopefully this has rectified the oheat issue for now. 

I do agree that the water channels are probably a mess. But perhaps its one of those cases of if it ain't broke....  

We will be taking it for a run on Pittwater this Sunday, hopefully we have done enough for now to stop the alarm. 

 

Now if only I knew where to find fish in Pittwater!

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Just an update for all who have been so helpful. 

Boat went on the water yesterday and there was no sign of overheating problems during the trip!

Thanks again. 

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