Shared water system on twins?
 

Ever since I had an overheat because of a bag sucked into a sea strainer, I've been wondering about setting up the raw water systems in a twin-engine boat so that one side can help the other if something gets plugged up. My boat has closed cooling (except for the exhausts), but I think that the principle would work on any twin.

As I see it, you would need to interconnect the lines at two points - once before the sea strainers (to deal with a plugged pickup) and once just before the water pumps (to deal with a blocked strainer). In order to keep one engine from sucking the water out of the other when you are running at low speeds or on only one engine, would you need check valves between each pickup its sea strainer, and again after the sea strainers?

I'm pretty sure that I recently saw pictures of a race boat rigged like this (Zenetics?), but I don't remember the details of the plumbing. Anyone out there ever done this?

C_spray,
That is a great idea , We have done it a couple of times, never needed a check valve. We just connect after the strainer. I have never seen a pickup plug up without plugging the strainer. However a pickup could plug if using the drive pickups, so before and after the strainer could'nt hurt with Bravo's

MBAM - The reason that I'm thinking about cross-connecting bfore the strainers as well as after is that I'm using Volvo DPX's. The water pickup is a 1/2" hole on the very nose of the bullet, with a pressure bleed-off hole on the bottom of the bullet, about 4" back, just in front of where the skeg starts.

If you hit a chunk of wood dead-on, you can sometimes jam it into the pickup. This hasn't happened to me - I've just had a couple of experinces with plastic bags: Once at idle speed (I just stopped, reversed the boat, and cleared it) and once at speed where a piece about 3' by 4' got sucked up, and flattened itself on the screen of the Gil strainer. That was enough restriction that the water pump cavitated and stopped pumping. Thank God for EFI computers - when the temp got to 200, the engine went into slow mode (2000 rpm).

Now that I think about it more, I guess that a cross-connection after the strainers would be all you need....

I'm not sure why I thought check valves might be needed, but the reasoning seemed logical at the time.

Would standard 1 1/4" ID hose do the job?

I think I would rather have the alarm go off to let me know the engine is getting hot.The drive uses water to cool it.You might cook a drive if you don't know your not picking up water.