Overheating Volvo 260/275

[Tommywalton]

Ok, I found through help Here that I am sucking air right under my gearbox below exhaust bellows on 275. No problem, I'm ordering parts but in the mean time I tookl it to the lake, 1/2 mile away. To test the new impeller and engine. The drive was totally submerged and the raw pump works fabulous. Ok here is the issue. My stupid mistake as I don't understand the cooling system obviously. Don't be too hard on me. I left the thermostat out because it was nasty looking. Obviously without it water bypasses the engine almost totally. Can someone help me to understand the cooling system? I've looked on the forum manuals and found nothing. I need part numbers. I need thermostat and the retaining parts. The number on my thermostat housing is 855470. Please help.

 

[NHGuy]

Re: Overheating Volvo 260/275

Get as much info as possible together. Have your engine size, production date and type, have your serial # and the # for your drive etc too.
Now start searching for the parts and make sure it all matches. If in doubt call a pro and avoid returning wrong stuff!

 

[Tommywalton]

Re: Overheating Volvo 260/275

Dang.. Ok here's my deal. This boat came with a 225, I don't remember any other numbers. I replaced it with a 350. It was a 305. I swapped in a long block and did not use the valve covers and they are now gone. Everything worked fine all last year. Where would I find the 225 models? When I order parts like thermostat, it will be for that model. But first I need to understand the cooling system. I need too make sure my intake gaskets Are not restricting flow. Or head gaskets. I just rebuilt this engine again. I melted it last year. Long story. My thoughts were, no thermostat, cooler running engine. I hope I'm wrong and all I need to do is get a new thermostat and not change gaskets or something. Is this making sense?

 

[Tommywalton]

Re: Overheating Volvo 260/275

I have searched this site for 3 hours about thermostats. Mine is out right now and im running hot. this is making very good sense to me. however i have noticed there are two main points people are arguing. with the thermostat out it will run hot because of fast circulation and the water will turn to steam and its just stupid to do. and some say the engine will never reach operating temp and i know all the consequences about that. only one can be correct in my case. anyway im putting it back in tom and trying again.

 

[cr2k]

Re: Overheating Volvo 260/275

You need the thermostat. Without it the water will flow so fast as not to absorb heat. It also keeps the flow going through the block as without it there may be pockets that will overheat or trap air.

Kinda like a 2 stroke wont run good with out a muffler for back pressure.

 

[captmello]

Re: Overheating Volvo 260/275

AQ225 parts are right hear. Can get them through Iboats. I bought my thermo at Napa. 160 deg. remember the thremo sits up inside the housing with a retaining clip to hold it in place. Use a standard 350 thermo gasket between the housing and intake.


http://www.volvopentastore.com/AQ225/dm/*******.082389462--**********.529322187--store_id.366--view_id.342844

 

[Tommywalton]

Re: Overheating Volvo 260/275

Upside down? Mine was installed with the spring down, pointy site up like a car Spring facing intake manifold. Is this incorrect

 

[captmello]

Re: Overheating Volvo 260/275

Upside down? Mine was installed with the spring down, pointy site up like a car Spring facing intake manifold. Is this incorrect

not upside down, up inside the housing. Some people get confused on where the thermo goes in the housing.

 

[Tommywalton]

Re: Overheating Volvo 260/275

Haha then mine was ok, I think I have it figured in my head what's up. The raw pump feeds the housing and into the water pump. Water circulates through engine passages. T-stat is closed. When closed it completely blocks maniflold flow. Also causing restriction and allowing a few ponynds pressure to build, thus letting heat transfer to water. Then t-stat opens and so on..