Air lock in cooling system?

[dsiekman]

Twin 2000 (Charcoal colored blocks) 5.0 VP Gi's with approx 190 hours.

I had the boat dropped in yesterday. Anyway, both engines fired off just fine, smoked a lot from the fogging oil, but got me to my slip just fine. When I got to the slip I shut down and popped the engine hatch to do a quick visual. I noticed that the risers on the stbd engine were hot to the touch compared to the port. The engines only ran about four minutes...if that. I seemed to have missed a ground when rewiring the dash, so the stbd gauges and a majority of the port gauges were not working. So, no temp readings. Last spring when I bought the boat we had a similar issue. We replaced the impellor, but it seemed not to want to draw water until I goosed the throttle. Once primed it seemed to work just fine all season. Any ideas? Is this a VP thing or something more serious that I need to look into?

In the interest of full disclosure, I started the port engine on a hose on Saturday. Thought I was going to sink the boat on dry land when the hose blew out and started filling the bilge. Whoops. :facepalm:

 

[Don S]

Re: Air lock in cooling system?

Sounds like you may have an air leak in the cooling system somewhere on the pickup side, or possibly plugged manifolds and risers. Do you boat in salt water?

 

[dsiekman]

Re: Air lock in cooling system?

Brackish. The odd thing is that at the beginning of last season when we bought the boat and end of the season when we put her away, I tested the temp of various parts of exhaust system with a laser thermometer. It was consistent from side to side, engine to engine within a couple degrees. All parts of the system were just warm to the touch and I could leave my hand on them without getting burned. If I remember right, they were running about 105-110...although I may not be remembering right.

 

[dsiekman]

Re: Air lock in cooling system?

Update - Went to the boat today and pulled the sea water pump. It appears to be fine. There was water in the lines both coming and going. Impeller was still in tact. I also pulled the hose going to the tstat to look for blockage - nada. What's the deal? Do I need a new pump? Could it be the circulating pump, not the raw water pump???

 

[Don S]

Re: Air lock in cooling system?

Go to the link below, and download the file and have a read.

http://www.4shared.com/file/50572185/e88f1d89/Volvo_Penta_Overheat_Diagnosis.html

 

[dsiekman]

Re: UPDATE - Air lock in cooling system?

Re: UPDATE - Air lock in cooling system?

Okay, so the raw water pump was sucking air where the plastic parts join the metal housing of the pump. Replaced with a new VP solid bronze pump. I also replaced both temp gauges with new Faria gauges to match the existing. Port engine (untouched) still runs at 160. Stbd engine (new pump) wants to run at about 170. It ran at 160 all of last year. To make matters more bizarre, on the stbd engine the port manifold runs at about 115-118 and the stbd runs about 10 degrees hotter. What's the deal?????