Extracting the thermostats tmd 40b

"Good morning gentlemen,
I ha

"Good morning gentlemen,
I have a boat with 2 TMD 40B and I would like to extrat/dismantle the thermostat for checking and buy a new one if this is the case.(my engine overheating over 3000rpm).
I can see 4 bolts on the upper side of the fresh water expansion tank. if unscrew this 4 bolts can I extract the thermostats or also need something else ?

Thanks
Dimitris - Greece"

Your engine most likely has 2

Your engine most likely has 2 thermostats and of DIFFERENT setting. Replace the both!

You are correct.

But my qu

You are correct.

But my question is How to dismantle the top cover. only by unscrewing the 4 bolts or I have to do something more....??

"Just take off the cover.
Se

"Just take off the cover.
See pic:
"

"Thank you very much for your

"Thank you very much for your help.

I have checked abv site and it seems that my engine is the TMD40A ... Because my fresh water expansion tank looks like this and also i have a plastic expansion tank..

%2C0800B.aspx?AddToCart=10,[url]http://www.marinepartseurope.com/en/volvo-penta-explo dedview-7744060-02B-02B,,,0800B.aspx?AddToCart=10[/url]


At part 14 is also attached the items 44,43 , 43 (ok it is easy to dismantle this and also the item 15a which there is a steel pipe leaving from there and goes through the head of the block somewhere....

Most probably I have to dismantle also this pipe...
Therefore seems I have a lot of work to do and also i think that once i have to do all these is agood idea to replace the antifreeze water.

Morten thank you for your valuable advises...It helps a lot. Today I will do the job and I will revert tomorrow with the results...

Thanks Again."

"If You have the A version wit

"If You have the A version with plate-cooler, remove it and send it to a radiator shop for cleaning. I doubt thermostats alone will cure Your problems."

"Actualy I have done everythin

"Actualy I have done everything with this expansion tank.

Last year my mechanic, clean same and put it back without any improvement...

The only thing which I haven't check is the thermostat (which is also the less expensive itam).
As far as I know in these engines, they are 2 type thermostats...
One type open at 70 C and the other type open on 76 C.
I will use the first type because here is GREECE (very hot weather and also hot sea water approx 20-22 C).
Also pls note that I never push the engine to the limit i.e. passing the 94-95 degrees because it is old engine and I dont want to have more problems.
Any way I will dismantle all these items and I will also change the radiator with a new one .

I will keep you advised abt all these changes.

Thanks again for your help."