Volvo D 255 loss of wtaer

[BW - Catana 471]

Running my catamaran’s Volvo D225’s for a number of years without issue Except. One of the motors, usually while sailing for hours can seemingly lose the water column between the impeller and the raw water intake.No amount of brief running can re-establish raw water circulation. Tearing apart the system and re-priming it solves the issue but what a hassle. Any ideas?? Thanks

[team karst]

Likely a vacuum leak towards the thruhull. I like to install a clear vinyl hose on the output of the rw pump. If u see bubbles in the hose, determine the source. Hose clamps, orings, loose or unsealed pipe fittings etc

[catalystcat]

Another possibility, check the seal on the raw water filter. Even if it seems snug and in decent shape, it can let air in. A little pool lube or similar on the seal can sometimes do the trick. Also, look for tiny cracks in the lid, especially around bends or corners. They can be hard to spot. The raw water lid and seal are spares I learned to carry after a while.

[DougR]

THe above ideas are good. It could also be that air is getting into the water pickup thru natural wave action, bubbles, etc, and then the pump has enough wear that it just can’t pull suction with the air, but will pull water with no problem.

Check for impeller wear, front cover plate and rear of pump body wear.