This is one where I think I know the answer, but there's something to drilling a hole into a hull that gives one pause. I checked the archives but couldn't find anything specific to installation. I wanted to install an external strainer to the thru-hull to compliment the in-line strainer. Had a bad experience where the entire thru-hull got plugged and thought an external strainer would help reduce the chance of that happening again. Its been recommended that I go with one with a clean-out door to keep barnacles from finding permanent homes. The question is the installation. With the plywood backing of the thru-hull, I expect to simply drill and mount the strainers, with sealant for the screws. Any additional advice, critique and confidence building that could be offered would be greatly appreciated. Just the idea of holding a drill to the hull has me queasy. As always, appreciate the advice.
Thru-Hull Strainer Installation
- Thread starter PHitchcox
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Strainer
I've never seen one with a "clean-out door" but I did have a scoop type strainer on a previous boat that I removed when I replaced a standpipe exhaust with a waterlift muffler. Theory was that the scoop could force water to fill the muffler & back up into the engine while under sail alone. After removing the strainer I immediately started picking up seaweed and plugging the inline strainer as this boat had a fairly shallow pickup. Next season I put the scoop strainer back on but drilled holes in the back end of it to keep pressure from building up & had no more problems. I attached it by drilling 1/4" deep holes in the glass (not going through the hull) & used 3/8" stainless sheet metal type screws with some marine-tex on the threads to seal them from the water. I never had problems with barnacles growing inside or on the strainer in the 28 years I had that boat. I did have to open up the holes in the spring after painting the bottom as the bottom paint would tend to fill them in.
I've never seen one with a "clean-out door" but I did have a scoop type strainer on a previous boat that I removed when I replaced a standpipe exhaust with a waterlift muffler. Theory was that the scoop could force water to fill the muffler & back up into the engine while under sail alone. After removing the strainer I immediately started picking up seaweed and plugging the inline strainer as this boat had a fairly shallow pickup. Next season I put the scoop strainer back on but drilled holes in the back end of it to keep pressure from building up & had no more problems. I attached it by drilling 1/4" deep holes in the glass (not going through the hull) & used 3/8" stainless sheet metal type screws with some marine-tex on the threads to seal them from the water. I never had problems with barnacles growing inside or on the strainer in the 28 years I had that boat. I did have to open up the holes in the spring after painting the bottom as the bottom paint would tend to fill them in.
Face scoop strainer aft
In the Barnegat Bay region of New Jersey, we have a significant problem with eel grass. It can and does block the engine water intake freqently. I have added aft facing scoop strainers to both of the boats I have sailed there over the past 15 years with great success. Grass and other junk seems to flow under and past the strainer and I rarely have to clear my in-line strainer. This orientation also gets rid of the potential problem of water being forced up into and and flooding the engine when sailing. I have not had any problems with barnacles or other fouling of the strainer. This is an old debate here on the HOW site so you can check the archives. If you check the boats still in your local yard you will find at least 50% have aft facing external strainers. I contacted Hunter before I installed a strainer on my current boat (2000 H340) about the hull thickness around the intake. They said that the hull is approximately 5/8" thick, and if for some reason I drilled all the way through then they recommended that I should go ahead and through bolt it using some 3M 5200 as a sealer. I drilled some pilot holes and used short SS screws with 3M 4200.
In the Barnegat Bay region of New Jersey, we have a significant problem with eel grass. It can and does block the engine water intake freqently. I have added aft facing scoop strainers to both of the boats I have sailed there over the past 15 years with great success. Grass and other junk seems to flow under and past the strainer and I rarely have to clear my in-line strainer. This orientation also gets rid of the potential problem of water being forced up into and and flooding the engine when sailing. I have not had any problems with barnacles or other fouling of the strainer. This is an old debate here on the HOW site so you can check the archives. If you check the boats still in your local yard you will find at least 50% have aft facing external strainers. I contacted Hunter before I installed a strainer on my current boat (2000 H340) about the hull thickness around the intake. They said that the hull is approximately 5/8" thick, and if for some reason I drilled all the way through then they recommended that I should go ahead and through bolt it using some 3M 5200 as a sealer. I drilled some pilot holes and used short SS screws with 3M 4200.
I did both.
Paul, when I had my boat in Maine, I had no strainer on the intake thru hull and that summer took in rockweed 5 times and clogged the intake. It became a real nusance. The final capper was sitting in Newport harbor three years ago and charging batteries. I suck up a jelly fish - what a mess to clean.. It also helped me make up my mind. I put an integrated clam shell/ thru hull intake in. Over the last two years, I have had no problems with the intake. Also, I went thru a long debate on this site as to how to orient the slots. The consensus was to orient the slots facing aft. I did and have had no problems since then (knock wood). The two previous posts have hit it on the head.
Paul, when I had my boat in Maine, I had no strainer on the intake thru hull and that summer took in rockweed 5 times and clogged the intake. It became a real nusance. The final capper was sitting in Newport harbor three years ago and charging batteries. I suck up a jelly fish - what a mess to clean.. It also helped me make up my mind. I put an integrated clam shell/ thru hull intake in. Over the last two years, I have had no problems with the intake. Also, I went thru a long debate on this site as to how to orient the slots. The consensus was to orient the slots facing aft. I did and have had no problems since then (knock wood). The two previous posts have hit it on the head.
Question.....
I do not have external strainers on my through hull for the engine. I was wondering, what happens if weeds, plastic, jelly fish etc..get caught on the strainer rather than just the hole. I guess regardless of having one or not a dive is necessary? Or does the external strainer prevent this all together......
I do not have external strainers on my through hull for the engine. I was wondering, what happens if weeds, plastic, jelly fish etc..get caught on the strainer rather than just the hole. I guess regardless of having one or not a dive is necessary? Or does the external strainer prevent this all together......
The hope is....
the strainer prevents most of the flotsam and jetsam and jelly-fish from even starting the journey up the thru-hull. At worst, I guess they could cover the entrance with the suction from the engine, but would fall away once the engine was turned off. Far better than sucking something up and then cleaning it out. Had to take apart each section of pipe from the thru-hull to the in-line strainer while underway once; never again. Groco makes a version with a swing door to clean out barnacles; Forespar makes one one-tenth as expensive out of marelon but semi-permamently installed. So far, I think the latter is the way I'm going.
the strainer prevents most of the flotsam and jetsam and jelly-fish from even starting the journey up the thru-hull. At worst, I guess they could cover the entrance with the suction from the engine, but would fall away once the engine was turned off. Far better than sucking something up and then cleaning it out. Had to take apart each section of pipe from the thru-hull to the in-line strainer while underway once; never again. Groco makes a version with a swing door to clean out barnacles; Forespar makes one one-tenth as expensive out of marelon but semi-permamently installed. So far, I think the latter is the way I'm going.
thru hull strainers
Hi, PHitchcox! I just installed the marelon strainers on WWW.Escape. Hopefully, no more seagrasss and rockweed! I installed them grill aft, using 2 $6-1/2 screws in each (diagnally, with small pilot holes) to hold them tight to the hull while the caulk cured. Since the hull was already painted with ablative paint, I used fast set 5200 for the installation and made sure that the screw holes were well sealed. the installation went fine, just be careful not to drill too deeply into the hull
Hi, PHitchcox! I just installed the marelon strainers on WWW.Escape. Hopefully, no more seagrasss and rockweed! I installed them grill aft, using 2 $6-1/2 screws in each (diagnally, with small pilot holes) to hold them tight to the hull while the caulk cured. Since the hull was already painted with ablative paint, I used fast set 5200 for the installation and made sure that the screw holes were well sealed. the installation went fine, just be careful not to drill too deeply into the hull
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