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Old 03-13-2012, 09:56 AM   #21
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do you need a strainer

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Carey wrote:

I am somewhat reluctant to add the outer strainer, as I would have a much bigger problem trying to clear that strainer. It would involve me in a wetsuit, and a hull possibly pounding down on my head. My do me some good actually.
You bring up a valid point.* While we have perf plates over all the intake through-hulls in the boat and have never had one get covered or clogged with anything, we have had one issue and that was barnacles.*

We had an engine start to overheat once so we shut it down for the last part of the cruise to the bay we were heading for.* Knowing that the boat was past-due for a bottom job, we asked a friend who lived on the island and is a qualified diver to check our engine intakes.* Sure enough, the perf plate for the port engine was covered with barnacles.* The FL120 doesn't require a high raw water flow for effective cooling but the growth had reached the point where the flow was restricted enough to affect the engine cooling.

Obviously regular haulouts can help prevent this as can routine inspection by a diver.* This just happened to occur at a time when we had delayed our next haulout for too long and bottom growth built up before the next scheduled twice-a-year dive.

So a screen or perf plate can pose a problem under the right (or wrong) circumstances.* However, in these waters with the potential to suck up eelgrass I think I'd rather have something over the engine intake through-hull(s) and make sure the bottom was checked frequently enough to ensure that a problem like the one we had doesn't have a chance to occur.

I found it interesting that our boat had not been fitted with sea strainers during the first 25 years of its life that it spent in SFO bay.* It did have the perf plates over the intakes, however.* So perhaps long, tough, thin stringy stuff like eelgrass is not a problem in the bay, delta, and rivers down there, I don't know.


-- Edited by Marin on Tuesday 13th of March 2012 09:58:59 AM
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Old 03-13-2012, 10:44 AM   #22
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RE: do you need a strainer

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No tool seemed to work, to get around the elbow preceding the strainier, until upon further thought toward available tools brought me to the life-saver. I have this flexible pincher tool used for retrieving small objects which may have fallen in otherwise inaccessible locations. You push the plunger, and three little prongs with triangular tips come out of the tube and separate. This process allowed the tool to take about half inch bites of eel grass, and then drag that material and a few more strands out at a time.
*I remove the hose from the strainer and leave the hose attatched to the*thru hull fitting.* The I*use one of those hand held horns to blow out the debris in my suction hose.* Give the horn a couple of honks and the hose and thru hull fitting is cleared.* the trumpet on the air horn works as an adaptor to fit most any size hose.*
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Old 03-13-2012, 01:02 PM   #23
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do you need a strainer

I had sea strainers on all my intakes but always had a problem at anchor with the air conditioner and generator clogging up with sea grass...especially in the Florida Keys. The problem was solved when I added Buck Algonquin 10" x 5 3/4" (part # RSS-1000P) wedge shaped external scoop strainers. This is the one with the sliding perforated screen. If you do this, be sure to mount the one for the generator with the large blunt end facing the bow so as not to put any positive water pressure on the generator. Before I had it installed I put it up on a drill press and drilled a dozen or so small holes in the blunt end so that it would get enough water to run while underway. The one for the air conditioner benefits from a little positive water pressure.


-- Edited by Doc on Tuesday 13th of March 2012 01:03:26 PM
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Old 03-17-2012, 08:18 AM   #24
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RE: do you need a strainer

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rwidman wrote:Keith wrote:
I saw a neat setup one time. Straight mushroom through-hull, then a piece of pipe on the inside. There was a tee in the pipe. A short piece of pipe sticking straight up with a cap on it, then the tee went to a strainer, then on to the engine. That way, if anything got hung up ouside, you could just open the cap and ram a dowell or somehing down there to clear it. Work quick and you won't have too much water on board.

No seacock?
*

*Oops, yes, there was a seacock.
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Old 03-18-2012, 04:55 AM   #25
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RE: do you need a strainer

The Y type strainers from Sendure are my preference .

So good we install then on any marine engine on the FW side , after any rubber impeller pump..

Many of the older marine built , (not marinizations ) ,engines have no built in circ. pump like cars.

Keeping the chunks of a dead impeller out of the engine or heat exchanger at almost no cost can save a cruise!
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Old 07-31-2015, 10:32 PM   #26
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My boat has 1993 vintage twin Detroit 12v71TA's and no sea strainers for those engines...strainers for everything else, but not those. The seacock and hoses to the pumps are pretty large... like at least 4" ID maybe more. On trip from Naples, FL to coastal SC...no problems. But my air conditioning strainer gets an amazing amount of crap in it this time of year in just a week. Even found a small fish in there recently.

So I wonder how the heck my engines can keep from sucking up lord knows what when idling or underway if the AC strainer gets so gunky so quickly ?... I forgot to notice what the arrangement was on the outside the one time I've seen it hauled out. Presume a 4" ID strainer would cost a fortune.

Both Onan 20Kw generators have sea strainers...but not the big engines..I wonder how typical that is for that size engine ? I keep meaning to close the big engine seacocks and remove the hoses to see what's in there but afraid a gallon of water would spill out in the process. I should keep the seacocks closed when engines are not running but concerned I'll forget to open them one time I do fire up.
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Old 07-31-2015, 11:21 PM   #27
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You won't forget if you keep your start keys hanging on the closed seacock.
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Old 07-31-2015, 11:42 PM   #28
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They may have external strainers, which are becoming more common. What did your surveyor have to say about it when you were buying your boat? New Hatterases come so equipped. Since the engines only run when the boat is underway, the movement through the water cleans off the external grate. Generators and AC often operate when the boat is at anchor or otherwise moored, thus need internal strainers.

http://www.deepblueyachtsupply.com/m...coop-strainers
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Old 07-31-2015, 11:42 PM   #29
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I just added an external strainer to my genset intake, even though it has an internal as well. In certain anchorages the internal strainer and the hose preceding it would clog like crazy with grass, to the tune of me having to pull the hose off of the through hull and strainer to clear it. Once an hour on the hour, all night long. Joy.

Oddly, the air conditioner strainer does not clog.

I got a Groco external perffed strainer from Hopkins Carter, it is about 3 inches in diameter and is hinged, so if it does clog (which seems somewhat unlikely given its large size) it can be opened for cleaning.
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Old 08-01-2015, 07:17 AM   #30
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For clearing jellies from an air cond the stick from inside beats the swimming visit (at O dark 30) about 100-1!
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Old 08-01-2015, 07:28 AM   #31
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I think the issue is size of the demand versus the size of the intake.

In other words...what is the flow like being sucked in.

I have 1 inch demands on 1.5 intakes with no external screens.

Occasionally I clean the air conditioner internal basket, but the genset I hadn't cleaned in 3 years (not very heavy use) and the main only 2 times in 3 years of ICW travel back and forth to Fla.

I can only attest to flow...because of my travels...the conditions are varied but may never hit some real problem situations like Chesapeake jellies in the summer.
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Old 08-01-2015, 10:17 AM   #32
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They may have external strainers, which are becoming more common. What did your surveyor have to say about it when you were buying your boat?
Nothing that I recall, but he turned out to be not so great a surveyor....not terrible but he didn't really spend enough time for a boat that size and complexity. I might re read the survey to see if there is any mention of this and/or simply call him up to see how typical or untypical this boats configuration in that regard may be.

As to the other members comments about leaving the keys on the seacock...there are no keys (except to get in the salon or helm room)

As an aside, the engines can be started and stopped from three different locations on the boat....in the engine room (over 6 foot headroom, full beam), at the inside helm or on the flybridge.

FWIW, the procedure is to first turn on the ignition circuit breakers, then "engines on" toggle, and then momentary "start" toggle for inside helm and flybridge.

Procedure in engine room is ignition circuit breakers on (engine room has it's own breakers for that purpose) , then press momentary "start" button for each.

Also a button for "prime" but have never used it as the engines start in the same instant the start button is pushed. (aprox 280 hours since block up overhauls)

In contrast my Onan 20K generators, that have aprox 1300 and 1500 hours are much harder to start. Require a few seconds of preheat plus 2 or 3 tries at the start switch. But run perfectly after they finally start. I wonder if that is typical of those and why the difference compared to the Detroit monster prime movers..2 cycle diesel vs 4 cycle ?
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Old 08-01-2015, 09:30 PM   #33
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Most of the large sportfishing boats these days do not have internal basket strainers. They rely upon screens on the hull exterior. I think a lot has to do with the space the strainers would take up in the engine room due to the large size of the inlet piping.

If I had external screens and no basket strainers inside I wouldn't be in a hurry to add basket strainers until I had proved that I needed them. They are another piece in your engine room that will demand your attention as if you don't have enough things like that already and consume space you probably don't have.

I have been polling clients and yards about there experiences for quite a few years and looked at quite a few perforated and slotted strainers. Haven't heard complaints about either. What I have noticed is lots of big oysters, barnacles and other wildlife in slotted strainers and not much in perforated ones. I think they drift into the slotted ones and stay and just drift by the perforated ones. I have seen quite a few basket strainers that were in need of service.

This is one of those discussions that merits the old cliché "it all depends" which will work best for you...
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Old 08-01-2015, 11:03 PM   #34
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Growth on the Chesapeake Bay was bad last year. A friend of mine with a 41' SeaRay had an engine overheat due to his perforated strainer clogging up with what looked like a big mat of moss. My strainer is easy to get to and clean if required. I agree that "it all depends on which will work best for you"
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Old 08-01-2015, 11:27 PM   #35
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Originally Posted by Caladan View Post
Nothing that I recall, but he turned out to be not so great a surveyor....not terrible but he didn't really spend enough time for a boat that size and complexity. I might re read the survey to see if there is any mention of this and/or simply call him up to see how typical or untypical this boats configuration in that regard may be.

As to the other members comments about leaving the keys on the seacock...there are no keys (except to get in the salon or helm room)

As an aside, the engines can be started and stopped from three different locations on the boat....in the engine room (over 6 foot headroom, full beam), at the inside helm or on the flybridge.

FWIW, the procedure is to first turn on the ignition circuit breakers, then "engines on" toggle, and then momentary "start" toggle for inside helm and flybridge.

Procedure in engine room is ignition circuit breakers on (engine room has it's own breakers for that purpose) , then press momentary "start" button for each.

Also a button for "prime" but have never used it as the engines start in the same instant the start button is pushed. (aprox 280 hours since block up overhauls)

In contrast my Onan 20K generators, that have aprox 1300 and 1500 hours are much harder to start. Require a few seconds of preheat plus 2 or 3 tries at the start switch. But run perfectly after they finally start. I wonder if that is typical of those and why the difference compared to the Detroit monster prime movers..2 cycle diesel vs 4 cycle ?
the prime button might be to pre lube the engines before you start, i have been on a few boats that have that system,it is good to use if they havent been run for a while, or it could be to prime the fuel during a filter change. but if it is on the dash board it is for oil.i deliverd a few of the way back when they wer built in the old lazzar factory in saint pete florida
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Old 08-03-2015, 02:28 PM   #36
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the prime button might be to pre lube the engines before you start,
That sounds like a good feature to have but my 12v71 primer buttons are labeled "fuel prime".

Ironically the generator fuel primer buttons are labeled just "primer" but I know are also for fuel priming as I have used one of them for such.
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Old 08-03-2015, 03:28 PM   #37
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All we have is a through hull flanged port. No grillwork or screens of any kind. Never had much to clean out of the strainer either. If nothing was to change I could go for 10 years w/o opening the lid.

Always had thoughts about getting a screened intake though.
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Old 08-03-2015, 04:27 PM   #38
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do I need to spend the 300$ x 2 for sea strainer?

YES‼️
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Old 08-03-2015, 06:21 PM   #39
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....do I need to spend the 300$ x 2 for sea strainer I am wounder how many people have them
I think it depends on the waters you boat in. How likely is it that your engine intake(s) will suck in something potentially damaging?

In this area eelgrass grows all over the place in water 30 feet or less deep and one encounters individual strands to dense mats of it everywhere, particularly in the current lines and tide rips.

Eelgrass can easily thread its way past a lot of the external grill or perforated plate designs. Unless there is a sea strainer in the raw water line the strands can end up in the raw water pump where it has been known to clog the intake and output ports and even wrap itself tightly around the impeller shaft.

Our boat, which spent the first 25 years of its life in SFO Bay until we bought it in 1998 and trucked it north, did not have sea strainers on the raw water intakes. Perhaps they are not so necessary in the bay, delta, and Sacramento River, I don't know. But knowing what kind of debris is in the waters here, we had big sea strainers added to the intakes before the boat went back into the water after being offloaded from the truck.

It already had perforated bronze plates (cups, really) over each raw water intake in the bottom of the hull.

A friend once had eelgrass clog the entire hose run from the engine's raw water intake through-hull to the sea strainer. His boat does not have any sort of screen, grill, or perforated plate over the engine intake. It took him some two hours to remove all the grass from the hose. But the sea strainer prevented any of it from making it to the engine's raw water pump.
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Old 08-03-2015, 07:37 PM   #40
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Marin,
I don't read anything in the above post that would support the need for intake screens. Yet you put them on straight away. I probably should follow suite. Didn't even think of it though. Had the seacock replaced too. Where's the grass around here?
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