Volvo Penta AQ170 overheats out of a sudden

[R0yall]

Hi there,

I just bought a boat with a volvo penta AQ170 motor which runs very good. Everything works as supposed and the engine stayed cool.
On my second boat trip there was a very shallow canal which caused a plastic bag and a tshirt wrapped around my prop. After removing it I noticed my engine temperature was in red which scared the crap out of me.

I waited for the engine to cool down and went back home (which took a few engine pauses to reach). The next day I tried the engine again in idle and the temperature goes towards 70% in a matter of minutes (idle).

The first thing I checked is the water pump impeller which looked great.

http://imgur.com/RMU371X

The above is how it looked. I took it out and put it back with some new grease.

Next thing I did is disconnecting the water pump intake from my sterndrive and connected a hose with a bucket of water on it to test suction. Well, the bucket got sucked empty so my guess is the suction is fine.

Next thing I did is check the thermostat by putting it in a pan of boiling water. The thermostat opened and closed just fine...

Now comes the weird part. I let the engine run for few minutes till about 60% on the temperature meter. Then, I turn it off, wait for 2 seconds and turn it back on. 2 seconds after restart I notice my temperature meter going down to about 30% in around 10 seconds. After that it starts to climb back up slowly again. I thought this was very weird...

I hope someone can give me some tips and help me out!

Cheers,
R0yall

PS. Aside from cooling. The motor still runs great..

 

[Scott Danforth]

welcome aboard

I would replace the impeller anyway

also, check for debris in the cooling system.

if your motor has a heat exchanger pull the end caps and check for debris

if you have a heat exchanger, make sure the glycol side is full

 

[R0yall]

welcome aboard

I would replace the impeller anyway

also, check for debris in the cooling system.

if your motor has a heat exchanger pull the end caps and check for debris

if you have a heat exchanger, make sure the glycol side is full

I don't know anything about a heat exchanger or do you mean the oil cooler?
AQ170 doesnt has closed cooling.

 

[Scott Danforth]

Some did, some didnt, thats why i asked

 

[R0yall]

Some did, some didnt, thats why i asked

Well, thanks for the tip...

I guess thats not how the oil cooler should look like...

What to do now?! How can I clean the inside? Will all the oil come out if take it off? How do you remove the white oil filter (Sierra)?

 

[Scott Danforth]

you unscrew the oil filter

you back flush the oil cooler from the other end. its a tube with a bunch of small tubes in it.

 

[R0yall]

you unscrew the oil filter

you back flush the oil cooler from the other end. its a tube with a bunch of small tubes in it.

I fixed it! Temperature stays around 10% on idle Thank you so much Scott!

I didn't want the risk of letting oil out so I got a powerfull vacuum cleaner and sucked all the debris out which was enough apparently.

When I opened the oil cooler cap (removed like in the picture above) there was some oil and water coming out. I didn't expect oil there and I don't think it's a good sign. It was not much but maybe enough to worry for a leak in the cooler?

Cheers