Cleaning Thru-hull water intakes with boat in the water - ideas?

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Pegasus

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I'm looking for some creative ideas on how to clean the mussels from my inboard cruiser water thru-hull intakes while the boat remains in the water. The intakes for both engines and the genset are as in the attached photo with grates over them.

My current plan is to have one person in the water (SCUBA) and one inside the boat at the thru hull when doing this job.

My primary question is "how best to clean under/inside the grates of the thru-hull that are not easily scraped with a putty knife?" My current plan is to use a rifle barrel cleaning brush. Any other thoughts? This will be a semi-annual 'to-do' item from this year forward with the mussel problems accelerating.

Thoughts appreciated, Doug
 

Endurance

Well-Known Member
Unless I'm missing something, the guy inside the boat won't have anything to do. If you unscrew the through-hull from the hull, you will be gushing water. If you try to take the intake hose off the inside of the though-hull to gain an access point through the hose fitting, you will be gushing water. If you leave a hose on the through-hull long enough to keep the top of the hose above the level of the water outside the boat, the guy on the inside would be too far back to see or do anything unless he's an endoscopic surgeon.

I think your best bet is to do what you can from the bottom only or put the boat on a trailer. Maybe you can talk your dentist out of an old scaling tool to make the SCUBA work easier.

Technically, we're not supposed to scrape mussels off and let them fall into the lake. Something about the decaying bodies of too many mussels adding nutrients to the water causing a concern of an algae bloom like the one that closed Utah Lake for a time last summer. I don't know that anyone would give you a hard time about as few as you would be removing, but you might run into a over-zealous ranger.

I think yours is among the first of many such concerns we will be having.
 

Pegasus

Well-Known Member
Unless I'm missing something, the guy inside the boat won't have anything to do. If you unscrew the through-hull from the hull, you will be gushing water. If you try to take the intake hose off the inside of the though-hull to gain an access point through the hose fitting, you will be gushing water. If you leave a hose on the through-hull long enough to keep the top of the hose above the level of the water outside the boat, the guy on the inside would be too far back to see or do anything unless he's an endoscopic surgeon.

I think your best bet is to do what you can from the bottom only or put the boat on a trailer. Maybe you can talk your dentist out of an old scaling tool to make the SCUBA work easier.

Technically, we're not supposed to scrape mussels off and let them fall into the lake. Something about the decaying bodies of too many mussels adding nutrients to the water causing a concern of an algae bloom like the one that closed Utah Lake for a time last summer. I don't know that anyone would give you a hard time about as few as you would be removing, but you might run into a over-zealous ranger.

I think yours is among the first of many such concerns we will be having.

My thinking was we could put a plastic garbage bag over the thru-hull under the water and remove the interior hose and clean the intake grates from the inside with a smaller toilet bowl brush without a big gush of water coming through - this will be easy to verify just by opening the thru-hull slowly and seeing what happens - and closing quickly if too much water is coming in.

I truly hope it isn't a problem to clean engine and air conditioning intakes while the boat is in the water. I'm not talking about cleaning the entire bottom, just the intakes! It would not be physically possible for every year-round in water boat to but hauled to do this twice a year. Logistically (and expense wise for boat owners) this would be a nightmare.

And I do agree that this issue is going to be everyone's issue very soon.
 
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Endurance

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I think the plastic is a great idea. Maybe you could use something a little stronger right under the through-hull then cover it with the plastic. That would avoid the moment of d'oh followed by panic if you inadvertently poked something sharp through the plastic.

About avoiding the long arm of the law, my experience is that most of the ranger staff is trying to do the right thing and that they are smart enough to know the difference between scraping a whole houseboat bottom and cleaning some intake grates. So long as you pass the attitude test, I'm betting they would exercise their discretion and not cite you for intake grate cleaning. I did have one of them chew me out a few years ago for sweeping sand into the lake. Let's hope you don't encounter someone like that.
 

ScottF

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Hello Doug. It seems like you're leading the way for all of us in mussel prevention/cleaning. Thank you!

I don't really have anything to add. My current (woefully inadequate) strategy is to pull the boat every year or two, ask the marina mechanics to clean away the mussels, and hope what they do is enough. Will I end up with expensive repairs to water lines, filters, water maker, etc.? Probably.
 

Pegasus

Well-Known Member
Hey Scott, I worry that this is "the year" that mussels will begin impacting boat motors/gensets/water systems significantly, especially boats that are not maintained properly. I'm a huge 'preventative maintenance' guy, so the more I can do to avoid BIG problems later the better. The eye opener for me was leaving my dinghy in from last October until February - less than 5 months - and when hauling it out in February it had hundreds of small mussels on it - in the 1/16" to 1/8" size.

I'm not as much worried about mussels on the bottom of the boat (although I don't like them there!) as I am about them attaching to my water intakes and reducing water inflow to the point of engine/genset overheating and potential fires or other damage - any of these things could be catastrophic. I agree in pulling the boat every year or two to clean the entire bottom, but I don't believe that will be enough to avoid problems to internal propulsion systems. Additional diligence will be required to keep those water intakes open.

I already close my thru-hulls when the boat is not in use so no water can naturally circulate on its own. I would recommend you do the same. (I put big red signs on my keys reminding me they are closed so I don't accidentally forget) My overall goal is to keep mussels from ever populating anywhere from the strainers on, leaving my only areas of concern being from the strainers through the exterior thru-hulls. I posted on the 'old' message board about some UV solutions I'm still considering, but I have not pulled the trigger yet.

Back to the original post, this will be my first attempt at cleaning the thru-hulls via SCUBA, so it will be a learning experience. I've scheduled to do it in early April and will post results.
 

Pegasus

Well-Known Member
Update - My nephew Grady donned the dry suite today to check out water intakes. The good news is there were not as many mussels as I expected - a few but not horrible. There were a few mussels on the shafts/props/strut box but not horrible. There were quite a few on the trim tabs. IMG_20170408_1308288.jpg
 

Pegasus

Well-Known Member
We ended up using a putty knife, a screwdriver, and a couple of bristle brushes to clean the intakes. Back to my original question - how to clean the grated intakes for the motors - we did not have to address cleaning mussels out of the inside of the grates this trip. Next update, this summer. -Doug
 

TYme2Fish

Well-Known Member
Just a thought from me as I have zero experience in this matter. But wouldn't a stiff metal brush, like the ones found in auto parts store, do the job. It'll take rust off of metal. Plus with the multiple layers it'll reach in between the grates and rub it clean.
 

Doug Elworthy

Active Member
Would it be possible, and or effective to periodically do a hot water flush on the engines with earmuffs type connections using the water heater on board?
And possibly a hot water back flush for the thru hull intakes?
Thoughts??
 

Pegasus

Well-Known Member
TYme2Fish, I actually did use a strong bristle brush, not metal but stiff nylon - worked great. I also had several sizes of gun barrel cleaning brushes to get between the grates, but it turned out I didn't need them (yet).

Doug Elworthy, if you could back flush hot water, that may kill the mussels in the grates, but once they are there even if dead, you've got to break the dead shell away from the surface which is not easily done - they attach themselves pretty good - and clean out the shells from the intakes. I'll have to think about that idea a bit more.

Thanks both for your comments, Doug T.
 

Jim Morgan

Active Member
Doug,
We always shut all thru-hulls when we are not using. Leaving ac water pumps on all of the time is the worst thing. Mussels attach near currents in the water, which is why they like intake fittings. The bottom painting guys scrape off what they can and then treat with Muriatic Acid and finish by directing their power wash spray into the fitting. Bad ones they take apart and clean. We have outdrives and they have no mussels near the intakes. Our generator intake is rarely used and has no mussels. Our lake water intake is brushed with a pole brush every trip and has never plugged up. My understanding is that AC Water intakes are the main problem (constant flow)....We have rooftop units, so no problem for us. Our mussels are in the swim platform supports only. Coal Tar Enamel is our bottom paint, over a steel hull.
Jim
 

capt.catfish

Well-Known Member
i think we are going to try these guys this year for the engines and also hang one by each of our (2) water intakes for the a/c system for this year. we will see what happens. I am going to bridle two of them right over the outdrives and pray for the best.
http://www.dockdisk.com/copy-of-about

I, as I'm sure everyone else, would be very interested to know if these work for you. Would be nice if a solution was this simple, but my instincts tell me that it's unlikely.
 
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