Removing Old Seacocks and Through Hulls

Thanks to my (our) good friend Parks I have completed my first thru hull/ seacock replacement. I cut the 1 1/2" NPS Groco thru hull to the proper length, bedded the Groco backing plate (a great way to go) in thickened West and all worked out great. One more shout out to Parks for his patience and commitment to taking care of my needs during my "learning curve"!!


1983 Present 42 Sundeck
Twin Lehman 135's

Great looking work, Steve. Hope mine turn out as well; just waiting on Spring to get started.

Is that a Fein Multimaster toolbag? Did you use it to remove the old one?

Good Catch Angus99! I did try to split the original valve laterally, and did with the Fein but still no luck. I was going to drive a short piece of round wood dowel rod into the thru hull and use this to center a hole saw which would have worked well as was suggested. The dowel size I grabbed was too small so I took plan B (kulas44) and used a 4" side grinder to grind the mushroom head off, which also heated the old glue. Came off like a champ!


1983 Present 42 Sundeck
Twin Lehman 135's

Forklift, thanks for your kind words. I noticed you used 5200 like a real man. Well done.

Ha Ha!! Now I have a silly question. Since all the sea strainers/ thru hulls have been cleaned, serviced or replaced I have to purge the air out of the lines and strainers when we are dropped in the water. Normally in a haul out I would close the sea cocks before being lifted out of the water and it avoids the problem of purging.
So....
Next Friday when we get splashed could I:
Have all seacocks closed, pull the cap on all four sea strainers, fill them with water from a hose, along with the hose going to the seacock and put the caps back on. I'm hoping to avoid wrestling with removing hoses at the heat exchangers, etc when the Travel lift sets us down. It seems that if most of the system is "precharged", when I open the seacocks while in the water the raw water pumps/ AC pump may purge the remaining air out. Has anyone tried this??


1983 Present 42 Sundeck
Twin Lehman 135's

That looks like a nice fix . I like it . I need to replace all of mine .Forklift you know high quality tools .I still want your lathe .

Steve your engine cooling pumps will move the air through the system and self prime very quickly. If you want top up the strainers it won't hurt but I dont think you need to.
The air conditioner pumps being centrifugal are mounted below the waterline and should be flooded. When you start them check the discharge to make sure they don't have an air lock. If water doesn't come out pretty quick, you'll need to crack something on the discharge side to let the air out and the water into the pump.

️Roger. Thanks Parks


1983 Present 42 Sundeck
Twin Lehman 135's

Steve, I`ve been on boats put back in the water, the operator holds you while you start the engine(s). After an agonizing 15 seconds or so water flows at the exhaust, I`ve not heard of pre filling strainers.

Hold your hand, or have someone else do it, on your engines raw water pump impeller cover as you fire up the motor. You should feel the cover cool off fairly quickly after you start the engine as the pump catches prime and starts pumping. If it gets warm to hot shut the engine off as the pump is not priming.

Forkliftt said:

Thanks to my (our) good friend Parks I have completed my first thru hull/ seacock replacement. I cut the 1 1/2" NPS Groco thru hull to the proper length, bedded the Groco backing plate (a great way to go) in thickened West and all worked out great. One more shout out to Parks for his patience and commitment to taking care of my needs during my "learning curve"!!View attachment 37794View attachment 37795View attachment 37796View attachment 37797


1983 Present 42 Sundeck
Twin Lehman 135's

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Looks really nice with the backing plate. The only input I would have is using 90 sweep fittings instead of 90 degree fittings. They catch less grass and have less water resistance which provides better unrestricted flow.

Thanks Pgitug. What is a sweep fitting? The new install is a slow radius so it might be what you are referring to?
The seacock/ backing plate I removed (not original to the boat) had a rotten plywood backing plate. The more I studied the correct material to use on the backing plate, and the labor cost, the more I hoped that something was already available. Parks put me on to it, and the cost is very reasonable.


1983 Present 42 Sundeck
Twin Lehman 135's

Yep. I do believe a slow radius is the correct term for the 90 I was referencing.

You know- now that I look at it, it is more 90 than slow radius. I suppose I can manage with it though.


1983 Present 42 Sundeck
Twin Lehman 135's

That is a sweep 90. You can tell by just looking at the picture.

Since the subject has come up, I shipped Steve a Perko Hose to Pipe 90. I consider it a sweep type elbow. I'll post pictures of the Perko fitting and the equivalent Groco so you can see the difference.



With it's more gentle curve, I think the Perko is a better elbow. The thing is, the Groco is significantly cheaper than the Perko. Is the Perko worth spending more money on? Would you pay twice as much for the Perko? 25% more? Give me a number.

Without seeing the internal roughness, I would guess that the k value would be more than double the long radius to the short radius, as the short radius looks a tad square on the extrados. But come on, this is on the suction side of a positive displacement pump, with low volume, and low velocity. I mean your running the water thru a hull strainer, a basket strainer, and rubber hose with nipples. Generally speaking the thru hull, strainer and hose are all within close proximity to the pump, so the minor increase in the equivalent length of the system with an elbow is a really not a worry at all.

But the Perko is much prettier!

It's not the length of the bend, it's to improve the flow rate.
A 90 deg elbow(angle) will have a slightly slower flow rate than a 90 deg gentle bend, pipework benefits from reducing interior drag(due to sharp angles or rough interiors) to improve the flowrate. apologies for the different terminology. Personally I would have put an exterior scoop type strainer to help to force feed the engine but that's just a personal choice, not a criticism.
A wee tip, when the boat is on the hard, inspect the seawater impeller and give it a liberal coat of washing up liquid, when the boat is launched it will lubricate the impeller during the start up.
It's best done a couple of days before re launching to prevent the washing up liquid drying and getting sticky as that negates the benefits.
I found Parks (Hopcar) equally helpful finding an answer to my bow thruster control, nothing was too much trouble, very refreshing in today's society.

If anyone needs to change out a seacock valve in the water, there is a nifty little device available to avoid any minor floods. I haven't tried it myself but it looks like a good idea.

AusCan said:

If anyone needs to change out a seacock valve in the water, there is a nifty little device available to avoid any minor floods. I haven't tried it myself but it looks like a good idea.

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Now why didn't I think of that?
Too cool.
Here is a Groco 90 sweep,that is the type I used. The normal 90 degree fittings do reduce the water flow, but the main reason I use these is that when sea grass fills the strainer and then backs up in the pipe, before you catch it or the temp begins to rise, this fitting with back wash the grass out with less effort than a normal 90 will.

That is very cool! It could also be used on a small hull breach as well I suspect???


1983 Present 42 Sundeck
Twin Lehman 135's

AusCan said:

If anyone needs to change out a seacock valve in the water, there is a nifty little device available to avoid any minor floods. I haven't tried it myself but it looks like a good idea.

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unless that is the 2 piece Graco flange/ball valve seacock....

the video is more properly describing changing a "ball valve" underway.

not insinuating the best practice as actually using a proper seacock...but is a cool tool in case your make believe seacocks breaks off and you need to stem the flow till you pound in a plug.

AusCan said:

If anyone needs to change out a seacock valve in the water, there is a nifty little device available to avoid any minor floods. I haven't tried it myself but it looks like a good idea.

Click to expand...

Wow very cool little tool

Pgitug, that's an excellent fitting. Unfortunately Groco doesn't make it in the size Steve needed.
I see you're in Punta Gorda. Do you know the Navi-Gator restaurant up the Peace River? Food is good and it's a fun boat ride to get there. Small boats only.

Pgitug said:

the main reason I use these is that when sea grass fills the strainer and then backs up in the pipe, before you catch it or the temp begins to rise, this fitting with back wash the grass out with less effort than a normal 90 will.

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That makes sense.

HopCar said:

Pgitug, that's an excellent fitting. Unfortunately Groco doesn't make it in the size Steve needed.

I see you're in Punta Gorda. Do you know the Navi-Gator restaurant up the Peace River? Food is good and it's a fun boat ride to get there. Small boats only.

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You bet. We kayak all over the peace River launching at the Navi-Gator. Nice place to spend an afternoon.
Our weather has rewarded us lately. High 83 Low 60. We will take it. Hate to be north right now. An extremely long winter for our friends up north.

Any ideas on a slotted, raw water scoop ? The screw heads are buried under 8 coats of ablative, and the MSW seacock/ strainer/etc is mounted right above it, to it. Neither the MSW nor the head valve move at all, too...
TICK TICK TICK - I know

Welcome, while I don't have an answer to your specific question, you've come to the right place for advice and counsel.

As the OP for this thread, I thought I'd also report that I just had all 15 below-the-waterline through hulls removed. Getting ready to go back new throughout.

angus99 said:

Welcome, while I don't have an answer to your specific question, you've come to the right place for advice and counsel.

As the OP for this thread, I thought I'd also report that I just had all 15 below-the-waterline through hulls removed. Getting ready to go back new throughout.

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If I had to replace 15 thru hulls I'd look into consolidating many of them if possible.

Capt.Bill11 said:

If I had to replace 15 thru hulls I'd look into consolidating many of them if possible.

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That's part of the plan. All but 5 of them are in a sea chest. Thnx.