External clamshell water inlets.....

[Genesis]

I dunno.... A hacksaw blade won't turn to the right angle to cut, unless you make a "V" from each angle, and there isn't much sawing clearance.

I'm going to dremel them out myself, but that won't work underwater

I remember being under the boat (diving) a couple of months ago and seeing some growth, and cursing quite loudly as I couldn't figure out how I was going to get at that - nor could I come up with a quick way to cut a couple of the tines.....

 

[MikeP]

They make a tile-cutter "blade" that is essentially a short piece of thin steel cable impregnated with carbide or some such material (Home Depot). You could insert it up over the tine and then bring it back down on the other side. A minute's worth of sawing should do it. Just like using emery strips to polish crankshaft journals!

 

[Nonchalant1]

Karl,

I think there's a math quiz first. Maybe you should measure the total surface area of the current slots and compare to the total surface area at the most restricted part of the intake pipe to the strainer. If the current slots have more open area (after cleaning off all bottompaint) than the cross section of the intake pipe, you won't gain any cooling capacity by taking bars out of the clamshells. I have a little ski boat with a 1 inch raw water intake with no strainer and it's amazing how much garbage it can pull in. A few medium size sticks or tough seaweed stems and you're going have a diving and underwater swearing day cleaning out the intake elbows.

If you do decide to do it, the clamshells are not attached to anything except the hull. Are they bolted into a plate or screwed into the hull? If it's a bolt, you could take them off and do it on the bench. I would hate to touch a screw into the FRP hull though.

Doug Shuman

 

[Genesis]

The clamshells are already off, and they are just screwed into the hull. They were bedded with what looks like RTV! That's definitely wrong - 4200 is going BACK on them when I'm done.

Its not just total surface area. The hydrodynamics are quite a bit more complicated than that, unfortunately.

Thing is, I'd rather have a mess INSIDE the strainer than OUTSIDE.

I've had a mess inside - but never outside - already. So the tines definitely aren't keeping the mess from ending up in the strainers as things are now.

 

[Traveler 45C]

Cut out the tines? I wouldn’t do it. Do they not provide an extra layer of protection? Why loose that? The stuff that collects in the strainers is small. Without the tines big stuff will get in…

And now a question about my set-up: Since I’ve got the screens (very small holes) on the outside of my hull, do I need to install strainers inside?

 

[Genesis]

Here's the problem - things get GROWING inside the clamshells behind those tines. You can't get to them. You saw the remains of what was up in my intake pipes - there's no way to get in there diving the boat with the tines in there and knock it off!

There's also no way you're going to drop strainers in the water. You CAN undo them, but then you have a problem - they need to be 4200'd back on to the hull, which you can't do wet. Now what?

The screen-style strainers are different.

There's a whole host of opinions on this - internal only, external only, both. I was a big believer that I was keeping crap out of the intakes with both BUT I've found plenty of seagrass in the stainer for the genset - the screen on that one is a VERY thin slotted one - and I also had a "hole-style" one that was competely obstructed with growth for my baitwell before. Now the baitwell doesn't get the use that the mains do in terms of water turnover, but still..... I've found OYSTERS in the main strainers before!

The counterargument for internal strainers is that they add intake resistance to the raw water system and this is undesireable. As far as that goes its true. However, my problem with the argument comes back to "where would you like to clean something out of IF it gets clogged - inside or outside?"

With the screens I see less reason for the internal strainers - but my view is that boats should have internal sea strainers. Its an "old school" thing, but that's always been my view...... if I bought a boat without them I'd add 'em - even though they're expensive and a bitch to find a place for.

 

[Avenger]

IMHO another big advantage to internal strainers is if you have crash valves, or have to resort to pulling hoses and dunking them in the bilge in a situation we don't ever want to face, the internal strainers will still protect your water pumps.

 

[Genesis]

BTW a big part of the reason many new "high footen" sportfish don't have them is that adding them requires larger intake piping to meet the specs for the pump (or you get overheating) and in addition they take up a LOT of space......

 

[Nonchalant1]

Karl,

How about replacing the screws that hold them to the hull with screwbolts that screw into the hull permanently but have bolt threads on the other end. You can then mount the clamshells with bronze locknuts. Then, since you're a diver, it'd be easy to take them off for cleaning and you could leave the tines for the protection they provide. If they need cleaning frequently, you could even mount them with clevis pins?

BTW - re: blue silicone....I understand that silicone leaves an oily residue that's impossible to remove and that makes 5200 and 4200 not stick well.

Doug

 

[Genesis]

Well I'm not sure exactly what was used to mount them before - but I think my strategy this time around is going to be to cut out one tine from each, then remount them - this should prevent anything big enough to jam in the pipe from getting in there, but allow enough access to clean it out if necessary.

If I have more trouble then I'll rethink this and do something else next time around.

 

[Traveler 45C]

I think removing only one tine is a good compromise.

My bottom cleaner asked me if it was ok for him to punch a small hole in my screens so he could get a screwdriver up there to clean it out. Can’t do it. Since I don’t have internal strainers, the junk that he would remove would end up passing through my raw water pump. No thank you…

 

[Genesis]

Yep. With only externals you must leave them intact.

If I had externals only I'd replace 'em with something that could be dropped in the water (e.g. a removable screen element)

I'm painting mine now, and will be over there tomorrow with both minus one tine each

 

[Traveler 45C]

If I had externals only I'd replace 'em with something that could be dropped in the water (e.g. a removable screen element)

Yea, those are destined for my intakes.