mercruiser 470 temperature problem

[Bigno89]

Good morning,
I am an Italian, owner of a Tullio Abbate that mounts a 3.7 LX, 470 mercruiser engine.
I use the boat in fresh water on Lake Garda.
I found this forum very interesting because it is full of very competent people and many of you have the same engine.
I write because I have problems with the temperature, when I go to 2000 rpm and 3000 rpm the temperature is stable, slightly higher than the average, when I stand still with the engine running the temperature rises a lot, the coolant flows out of the riser and goes into the container in plastic, a little liquid also comes out of the riser cap and starts to smoke in the engine compartment ... after having cooled the engine all the water from the plastic overflow container is sucked into the circuit and returns completely to the riser ...
What do you think it can be?
Sorry for my writing ...

 

[Scott Danforth]

First, welcome aboard

second, you have either a head gasket issue (extremely common) or a heat-exchanger issue or an exhaust manifold to riser problem. or you have a combination of above

when was your impeller last changed?
have you done a compression test?
drain the coolant and do a cooling system test (just like on a car)

has your motor received the updated heat exchanger?

you may want to start researching the mercruiser 470 and all the other updates you should be looking for.

these may include, however are not limited to:
water pump cam seal speedy sleeve repair
alternator conversion
4" heat exchanger upgrade
exhaust elbow upgrade.

 

[achris]

..I use the boat in fresh water on Lake Garda.. ...

Oh wow. When I come to Italy to ski at Dolomites, go first to Milan, then a bus to Campitello, so we go through Brescia, and Roverato, right past your lake!

Ok, the 470. This engine must have a good cooling system, or the overheating will damage the cylinder head gasket.

You must have the prefect condition water pump impeller in the drive (change every 2 years), then the heat exchanger must always be clean, every 2-3 years cleaning. When this is done, the water coming from the drive must be checked for only water, no bubbles of air. Also the lake water must also be free to leave the engine. So it must go through the exhaust elbow with no restrictions. We take the elbow off and check it's condition every 4 to 5 years. Clean and put back on, or replace with the new one.

Do you have an engine serial number? Or do you know is the heat exchanger 75mm or 100mm diameter?

The reason the coolant in the engine expands is because it is getting hotter, that is the reason why it has the plastic bottle to catch the water for going back to the engine when it is cooler.

I hope this is some help,

Chris.........
(Australia)

 

[Bigno89]

Thanks so much for checking me out!
The impeller was changed last year, in 2019 I made 10 releases, this year only 1.
The compression test has not been done, there is no trace of coolant in the engine oil.
I will try to replace the thermostatic valve, look at the impeller and clean the exchanger.
The serial number is 0468319.