Volvo Penta 350 overheating, 280 outdrive

Schonl

Cadet
Joined
Nov 5, 2016
Messages
13
Hello Everyone,
Need a little help with my overheating issue. Here's the history:
Began overheating while on the lake. Took it home and put muffs on and water was barely trickling out of the exhaust. So, I changed the risers, installed new ss gaskets, changed the impeller even though the old one was still soft and flexible, I changed the exhaust bellows and then installed new duckbill exhaust hoses that come out the bottom each side of the 280 outdrive. I did lightly sand the Johnson raw water pump faceplate to get the scale off of it with emery cloth. Not sure if that would cause a problem, I installed a new gasket when I changed the impeller. After all that I started it up and it's overheating again. When I crank it up and let it idle the temp will start rising continuously after it warms up. If I go up to 2500 to 3000 rpms the temp will slowly go down to about 160 then begin rising again. If I let it idle after going to high rpms the temp will climb pretty quickly as well. So I pulled the thermostat housing, removed the thermostat, installed a new gasket and cranked it back up, it began overheating again. It doesn't seem to be getting enough water, somehow. Any ideas as to what else I could possibly change or do to get this to stop overheating? I installed a new water pump about a year ago, it's not dripping or anything so I don't believe that's the issue. Thanks for reading this and giving any suggestions you may have. Hopefully Don S. will chime in, he's really good on these Volvo Pentas.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
Don has been boating with Jesus for a few years.

Back-flush the line from the raw water pump to the drive to flush out crud. Also, replace the raw water inlet casting on the drive (under the bellows on top of the pivot frame)
 

kenny nunez

Captain
Joined
Jun 20, 2017
Messages
3,056
When you back flush look closely at the area where the upper section of the lower gear housing in the front at the pivot point, there is an a?o? ring that can cause an air leak when the boat is on plane. The ?O? ring is easy to replace after draining the oil and removing a couple of Allen bolts.
 

Schonl

Cadet
Joined
Nov 5, 2016
Messages
13
I had no idea that Don was no longer with us. I apologize if I offended anyone with that comment. I've read so many of his responses on here and he knew his stuff, very knowledgeable. May he rest in peace.
Thanks guys for taking the time to help out. I went and back-flushed the incoming line to the raw water pump as suggested and it seemed as though pressure was building some then it began to flow back out of the outdrive, I let it do that for about 10 minutes. Then i connected the line back to the raw pump, started it up and wow, it won't go over 120 degrees and water is flowing really well out of the exhaust and duckbills. Now I've just gotta put the thermostat back in and take it to the lake for a on the water test. Thanks again for all your responses and for saving me money, lol.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
Most likely you have a bunch of crud plugging up your power steering cooler if you were building any pressure when backflushing
 
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