overheating/cooling on a volvo 270

[2stroke1971]

Bayliner capri, volvo aq125 with 270 outdrive...just bought it a couple months ago, havent run it yet, but should be ready to test it this weekend.

The previous owner told me up front that the sea water system had a leak or two, most noteably at the strainer neck of the exchanger. He said it needed a gasket. I saw a bunch of permatex there, he told me that it had dripped there pretty well. So, I pulled the connector, and the threads on one side in the strainer were gone, so there was only one screw on the flange that was holding it. Apparently that and a bunch of permatex was not enough!

I tapped the neck and placed a threaded insert, got a new oring and got that flange to seal up nice and tight with both bolts. Additionally, where the copper tube extends from that area where I repaired it, there had been some black heater hose connecting it down to the the copper pipe that goes in the underside. I dont know if this pipe had been all copper at some point or not, but I replaced the heater hose with some heavy reinforced clear tubing, thinking Id like to see how the water is moving.

So, I met the previous owner again recently to finish up some paperwork, and of course then he mentioned something about an overheating problem, now and then sort of thing.

I did some searching here and found some great info,paticularly a thread about the same power train as I have, about the water inlet neck and how if the seal is bad, it can suck air into the system at speed and cause overheating...but when running at the dock, or at low rpms, it would be ok. It sounded like what the previous owner had described. This thread also suggested a clear hose section, which as luck has it, I already have!

So...before I rip out the water inlet neck in a panic, does it stand to reason that having a leak elsewhere in the seawater system like the one tha I had to repair at the strainer neck could also introduce air into the system and cause the same overheating symptoms as the thread I found described?

I dont know if I wanna do the "take the prop off and dip the drive into a big tub of water" or just haul the darn thing down to the water for testing (but it is a 30 mile drive for me) but either way Im almost ready to fire it up....

Also help me with the terminology here..."raw water"..is that seawater?

Thanks,
Neil

 

[Bondo]

Re: overheating/cooling on a volvo 270

Also help me with the terminology here..."raw water"..is that seawater?

Ayuh,... If you're in the Ocean it'll be Seawater,... Otherwise, it's Whatever is Outside the boat....

Have you changed the raw waterpump Impeller,..??

Any Leaks, Upsteam, Before the raw waterpump will allow Air into the system...
Any Leaks, Beyond the pump will leak Water instead of Air...

 

[RicardoMarine]

Re: overheating/cooling on a volvo 270

A failing lower "pivot" tube O-ring, a corroded water neck and a worn special "beaded" water neck gasket, can greatly contribute to a suction leak since these are up stream from the actual sea water pump!
Put these on your to do list!

.

 

[Don S]

Re: overheating/cooling on a volvo 270

The seal on the water connection on the drive can cause an air leak, but on those drives it's very common for the connector (aka water neck) itself to corrode away right where the hose attaches.
Then, you have an air leak. When in the water and not moving, it will be underwater and work fine, but as soon as you move forward and the water level drops below the hose connection it then sucks air and you get an overheat. With that clear hose, you should be able to see air bubbles start if the connector or the gasket is leaking, but you will have to be in the water and moving to use that method, not on muffs.

 

[2stroke1971]

Re: overheating/cooling on a volvo 270

Thanks everyone!

I was told it has a new impeller....so that should be good. Im going to check out the neck this afternoon, and maybe the pivot neck...Ive got some good info on where the neck is, but where is the lower pivot at? I think I will at least make the first start in a tub and go from there.

Thanks again,
Neil