Raw Water Intake ??

[Ironworker]

I'm planning on a fresh water flush and a crash valve system for my new QSBs. I'm also relocating my raw water intakes. My question is there any reason why the two intakes cannot be tied in with a valve vs completely independent of each other?

[Tony Meola]

If the engines require a 1 1/2 inch intake and hose. Then the single valve would probably have to be 3 inches then you would branch off the single valve. The issue I have with it, is there is a leak in a hose for one engine you can not shut down just that engine.

I don't think a Sea Chest is viable on our boats, but I vote for staying with two intakes.

[Rawleigh]

I agree with tony. I think you would be complicating simplicity. Redundancy is one of the great things about twin engines.

[Ironworker]

My first post was not clear. I'm installing two completely separate through hulls, strainers etc. (one for each engine). I was just wondering why they couldn't be tied together with a valve that could be opened if necessary. I suspect it would be a waste of a couple of Tees, some nipples and a valve but I can't see where there would be any potential harm.

[mike ohlstein]

Because...... you sucked a plastic bag into one and it's clogged? You're better off going under the boat and clearing it. Unless you up-size both intakes, you won't get enough flow through one to cool both engines.

If that's what you're thinking, you can achieve more flow from one 2.5" hose than through two 1.5" hoses, but you have to maintain that size from the thru-hull to the Y valve.

A few elbows and a ball valve won't cut it. So the potential harm is in overheating both engines.

[Carl]

You can, but the question becomes why and what is the benefit of the extra complexity, extra work, extra expense and extra potential problems.

[Tony Meola]

Ok, I need a diagram.

Sorry but sometimes I need a visual.

I am not sure you really accomplish anything by doing this.

[scenarioL113]

I believe Rick is talking about keeping the 2 raw water intakes independent of eachother,

BUT there will be a "T" somewhere in the systems that will allow them to be opened to eachother ONLY when the valves are turned in the "crash/flush" positions.

If the valves are in the "RUN" position there is nothing that could effect the opposite engine bc the valve is "closed" that would be feeding the "crash/flush" position

[Carl]

Frank- I think I understand what is being asked, I'm sure it can be done...but what is the benefit.

Possible benefits I come up with

-only having one bucket/hose to stick the hose into for winterize or flush.

-if one motor sucked up garbage you could share the other intake...for slow running. But you can run slow on a single motor. Run hard and you risk overheating both...maybe to get out of the way quick or a quick run. But you can run dry for that too if need be.

-single crash line...problem with crash valves is stuff gets into the bilge clogging the line even with crash grates. OR motor clears out the bilge and now runs dry killing the impellor...in this case impellors.

Then again, maybe I'm reading it wrong. I'm thinking of it like he wants to pull fuel from a second source if one should be bad. I'm not sure that carries over to raw water intake. Eh...chances are I'm wrong in my thinking.

[Bruce]

I've seen it done on larger yachts. The premise being if the intake gets clogged really bad, eel grass etc, the primary intake can be closed and secondary valve to tie in the other intake is opened.

This was mainly done for slow speed docking ability to maintain control when you had super structure that acted as a sail. Obviously the tie in would be after the sea strainer.

Back in my younger days part time I captained a 60' Hatteras SF with enclosed flybridge. Out trolling and one engine started to overheat and steam. Shut down, went to investigate and strainer basket full of sea weed, cleared but upon start up it still overheated. A little rough for a dive over to check.
He had what Rick wants to do. Did valve change over, ran with both engines at just above idle back to inlet and docked. Needed it that day was a bit windy.

Got a diver out and it had picked up a piece of tarp in the intake floating with the weed.

[Ironworker]

I believe Rick is talking about keeping the 2 raw water intakes independent of eachother,

BUT there will be a "T" somewhere in the systems that will allow them to be opened to eachother ONLY when the valves are turned in the "crash/flush" positions.

If the valves are in the "RUN" position there is nothing that could effect the opposite engine bc the valve is "closed" that would be feeding the "crash/flush" position

Sorry guys to disappear for a bit. This is similar to what I'm discussing. I'm trying to simply the system not overly complicate it but I'm also thinking about the ability to "get home" if one of the intakes are clogged at just the wrong time. I've had some issues with this in the past in heavy seas and getting a man in the water in 8' seas is just not a good idea. Trolling speeds with two engines it better than single engine ops in heavy seas or close quarters.

I agree, a diagram is needed but I wanted to run it up the flag pole for your opinions before I invested any significant brain power is designing the system and buying pieces and parts.

This boat will be used in the southern Bahamas and I want to build in as much redundancy/reliability as possible within reason of course.

[Tony Meola]

Ok, now I get it.

Interesting idea.

[Carl]

As long as you know the system's limitations and feel better benefits are worth it, going that route makes sense.

Me...I like simple, so simple I removed my inline filters and now just have external eel grass strainers underneath. If it sucks up a bag...I shut motor, wait a few seconds, restart then put in reverse. Bag or garbage falls away when motor is off (Only a bunch of little holes in strainer so stuff does not actually get Sucked in, like many of the slots on intakes can be), reverse pushes whatever falls away far from the strainer so as not to be sucked up again.

Most times I have seen pump problems is bad connections and sucking air, or in my case not quite fully opening a valve. Somehow I have a strong feeling your connections will be spot on.

[Rawleigh]

Like Carl, I too put on the external strainers. Being a sceptic I also kept my internal strainers. I have never seen anything in them, and when the time comes for me to change hoses the internal ones will go.

[Ironworker]

I'm also going with external strainers but may add a secondary strainer as well.

I got my old engines out and we are cleaning up the rest of the hull before the build back. I should have made this decision 2 years ago.