Volvo Penta Cooling Puzzle

[bobgarrett]

I have a Volvo Penta D1-30 engine and have a strange cooling water problem I hope someone might be able to give a pointer to.

When we relaunched a few days ago I fitted a new impeller because I spotted a slight crack on one of the blades of last year's impeller.
Once in the water I started the engine and there was an initial rush of water out of the exhaust and then nothing. The marina dory took us to a berth as we needed to be away from the boat lift. I took out the impeller, saw nothing wrong so put it back in and tried the engine again. There was an ongoing feed of water out of the exhaust so I assumed it was maybe an airlock or "something" now solved.

Yesterday I started the engine to check it and it was ok. Then later started it again as we needed to move from one marina to another, and there was plenty of water through the exhaust so we motored for a while and then sailed for a couple of hours. When we got to the other port I started the engine and no water out of the exhaust. So we sailed as close to our new berth as we could with a plan to just use the engine for the final few minutes. We started the engine and now plenty of water out of the exhaust.

So what might cause the sea water flow through the system to the exhaust to stop and start? No water leaking into the boat, exhaust gases themselves were coming out of the exhaust.

My only thought so far is whether the sea-water pump might have lost some teeth and sometimes it starts going and once spinning it is ok. The other idea remains some form of airlock which started while ashore and then happened again when heeled for sailing.
I'd welcome any other ideas to check.

Thanks.

 

[vyv_cox]

When sailing the water drains out of the hose between the seacock and pump. Priming should occur naturally but if there is any air leak it will not. Check hose condition and all joints for leaks. If this does not fix it check the pump lid and shaft seal for leaks.

 

[boatmike]

Also check that all hoses are clear. Very often a failed pump impeller can shed blades or bits of blades that float around in the downstream pipework or the thermostat housing causing an intermittent blockage

 

[Bilgediver]

I have a Volvo Penta D1-30 engine and have a strange cooling water problem I hope someone might be able to give a pointer to.

When we relaunched a few days ago I fitted a new impeller because I spotted a slight crack on one of the blades of last year's impeller.
Once in the water I started the engine and there was an initial rush of water out of the exhaust and then nothing. The marina dory took us to a berth as we needed to be away from the boat lift. I took out the impeller, saw nothing wrong so put it back in and tried the engine again. There was an ongoing feed of water out of the exhaust so I assumed it was maybe an airlock or "something" now solved.

Yesterday I started the engine to check it and it was ok. Then later started it again as we needed to move from one marina to another, and there was plenty of water through the exhaust so we motored for a while and then sailed for a couple of hours. When we got to the other port I started the engine and no water out of the exhaust. So we sailed as close to our new berth as we could with a plan to just use the engine for the final few minutes. We started the engine and now plenty of water out of the exhaust.

So what might cause the sea water flow through the system to the exhaust to stop and start? No water leaking into the boat, exhaust gases themselves were coming out of the exhaust.

My only thought so far is whether the sea-water pump might have lost some teeth and sometimes it starts going and once spinning it is ok. The other idea remains some form of airlock which started while ashore and then happened again when heeled for sailing.
I'd welcome any other ideas to check.

Thanks.

Do you have one of those above waterline Beth's look alike transparent sea water filters. Some of these fail to give an effective seal and when the engine is stopped the water level drops to sea level pulling air nto the filter housing through a leaky lid joint. You can do a basic test by smearing copious amounts of vaseline on the lid joint and threads and see if things improve. Changing the lid seal might work.

 

[RichardS]

I have a Volvo Penta D1-30 engine and have a strange cooling water problem I hope someone might be able to give a pointer to.

When we relaunched a few days ago I fitted a new impeller because I spotted a slight crack on one of the blades of last year's impeller.
Once in the water I started the engine and there was an initial rush of water out of the exhaust and then nothing. The marina dory took us to a berth as we needed to be away from the boat lift. I took out the impeller, saw nothing wrong so put it back in and tried the engine again. There was an ongoing feed of water out of the exhaust so I assumed it was maybe an airlock or "something" now solved.

When you fitted the new impeller did you use plenty of lubricant on it? Assuming that you have greased any air leaks out of the filter system, then some systems still sometimes struggle to self-prime unless the impeller is well lubricated. A top up with water into the filter sorts it out.

Richard

 

[bobgarrett]

I did use the lubricant when fitting the impeller and given it has worked at times I am going to check for air holes that might be causing the water to drop out. Still seems strange that it sometimes works though.
Thanks all for suggestions I will check in a couple of days when back onboard.