GRP boat stabilization

[Granitu]

@ Granitu

Your idea of removing completely the thermostat makes a lot of sense.  The one i have is intended to open above 60C which is not very far away from our ambient temperature.  I might consider doing so.  With regards to flushing the engine after use, i wish i could do so but how can i do it when the boat is at sea and i dont have a supply of fresh water!

Your outboard engine is designed to operate at a specific operating temperature. This is controlled by the thermostat.
Removing the thermostat will cause problems in 2 stroke and 4 stroke engines.

The main problems you will get are, Inefficient fuel burn due to the engine components not reaching operating temperature and fouled ( even in a 4 Stroke) plugs due to incomplete fuel air combustion.
A four stroke will "make oil". This is when unburnt fuel passes into the crankcase and dilutes with the engine oil and causes the "Oil" level to rise instead of decrease. This has happened to me on my Honda BF50a when my thermostat got stuck open and i didn't realise, until it was time for an oil change which I do twice a season on the water. When i removed the dipstick it was completely covered in the oil petrol mixture with liquid visible in the dipstick tube itself.
Also important to note that the thermostat is there to control coolant flow into the coolling passages. This is done by restricting the coolant flow to allow it to transfer heat from the engine block onto the coolant efficiently. Removing the thermostat will not allow the coolant stream to transfer heat from the engine as this will flow too fast and only a fraction of the engine heat will be transferred. This will then result in the engine overheating when running a high rpms.

That is what I used to think, but you are playing it out too much by the book. Ideally, yes thats the way things should work but unfortunately, things do wear out and some outboard engines sometimes are better off without a thermostat, believe it or not.

Thats why this has to be checked out with a mechnainc - outboards are not the same mechanically.

[Icom]

Update re: overheating.

Im really shy to say that both the thermostat and the impeller where not functioning.  The thermostat was completely blocked half way and the impeller was thorn off the bushing!!!!  No wonder it overheated!  Got a new impeller and will be collecting the thermostat tomorrow. 

@ Granitu  My engine also has the hose adaptor attached.  Do you think i can use that?

[Granitu]

Update re: overheating.

Im really shy to say that both the thermostat and the impeller where not functioning.  The thermostat was completely blocked half way and the impeller was thorn off the bushing!!!!  No wonder it overheated!  Got a new impeller and will be collecting the thermostat tomorrow. 

@ Granitu  My engine also has the hose adaptor attached.  Do you think i can use that?

I think you could make shift - but i think you found the problem!!! If i were you, i would have a frank discussion with your mechanic and let him tell you in his opinion if they are likely to form salt deposits and see if its worth the hassle to rinse your outboard.

Some old and even new gen yammies suffer from this particularly the low hp engines (eg the 8hp enduro). However, i have seen mercuries running for 3 years with no rinsing and working as good as ever.... there is no clear rule unfortunately depends on the material used in the cooling system.... but i have seen badly blocked cooling systems... so it is worth to look into this.

And trust me no mechanic loves to clean a cooling system of an outboard from crystallised salt as it is a highly lenghtly and laborious exercise...