PDA

View Full Version : Thru Hull fitting questions


kbob
10-01-2009, 05:02 PM
I have a few questions before starting my ballast project:

- Does having a thru hull scooper installed with the vents facing forward (to scoop the water) put too much pressure on the lines and pumps when at higher speeds?

- Would it be alright to turn the thru hull scoop with the vents in the back to prevent any excess pressure on the lines?

-Is it better to close the shut off valve everytime the ballast is full...because that seems like a pain.

-Would it be better to add two or three drain thru hull fittings for better performance or tie them all together into one drain fitting? Would the extra thru hull fittings devalue the boat?

I'd appreciate any thoughts or opinions? Thanks in advance!

P-hat_in_Cincy
10-01-2009, 09:42 PM
I have a few questions before starting my ballast project:

- Does having a thru hull scooper installed with the vents facing forward (to scoop the water) put too much pressure on the lines and pumps when at higher speeds?

- Would it be alright to turn the thru hull scoop with the vents in the back to prevent any excess pressure on the lines?

-Is it better to close the shut off valve everytime the ballast is full...because that seems like a pain.

-Would it be better to add two or three drain thru hull fittings for better performance or tie them all together into one drain fitting? Would the extra thru hull fittings devalue the boat?

I'd appreciate any thoughts or opinions? Thanks in advance!

My opinions only:

1-2) I woouldn't put a scooper thru-hull on the ballast system...facing forward or rear. With aerator pumps, they have no way to prevent flow. With impeller pumps you MIGHT get away with it unless you plan on draing/filling out the same hole while under way. IIRC, in MC's stock system, they didn't use scooper thru-hulls.
3) 1st, I would put a manual shut off valve directly after the thru-hull. Closing the shutoff valve every time depends on your system design and what type of pump you use. Impeller pumps can act as their own check valve. Aerators cannot...without help.
4) Varying opinions on this. MC used 1 for 3 pumps. This requires the design/use of a manifold. I put separate thru-hulls for each pump (4). If something happens in 1 line of my setup, it won't affect the others. Both ways work. Regarding devalue...I don't know, but I hope not! :D

kbob
10-02-2009, 11:46 AM
I was just curious whether sucking something up through the regular thru hull without a strainer would be a problem. Thanks for your help!

jason@wakemakers.com
10-02-2009, 03:01 PM
Paul's the man when it comes to Mastercraft ballast installs, so definitely listen to what he has to say. Here's my input on your questions based on our experience:


- Does having a thru hull scooper installed with the vents facing forward (to scoop the water) put too much pressure on the lines and pumps when at higher speeds?

No, it doesn't create too much pressure for the hoses and pumps, so long as you're using impeller (Jabsco, Johnson, Simer, etc.) pumps. The amount of pressure created by the scoop is actually quite small. As Paul said, definitely don't use a Scupper for aerator pumps, you'll have water filling the bags all of the time with that setup.


- Would it be alright to turn the thru hull scoop with the vents in the back to prevent any excess pressure on the lines?

No, if you do that you won't be able to fill the system when running at speed, and the amount of pressure created is minimal. I agree with Paul though, I would use mushroom style intakes as opposed to scuppers. There's really no downside, and plus they're cheaper!


-Is it better to close the shut off valve everytime the ballast is full...because that seems like a pain.

This is unnecessary, the ball valve is really only there as an emergency shut off in case something down stream breaks. If the system is designed correctly you do not need a manual (or automatic) valve to be closed every time you're done filling.


-Would it be better to add two or three drain thru hull fittings for better performance or tie them all together into one drain fitting? Would the extra thru hull fittings devalue the boat?

This depends primarily on what type of system you're installing, and how you want it to function. With reversible pumps, most customers we speak with will use one thru-hull fitting for each ballast location, and tie the vent and drain lines together. That saves drilling an extra hole, but does cost more, so ultimately it just depends on how you want it setup.

Newer boats from the factory have multiple thru-hull fittings, so as long as quality parts are used, and the installation is done correctly, the overall effect on resale value should be an increase, as the boat will be more desirable with the ballast system installed.

kbob
10-02-2009, 03:30 PM
Thanks I really appreciate it. I'm sure i'll have a few more questions here in the future as i am trying to work out all the details. I love this forum, its such a great resource...as well as a good past time for a slow work day :)

TallRedRider
10-02-2009, 03:42 PM
My mushroom has a strainer on it. I would try and find one like it so that you can't pick up bigger debris. But it depends on the lake you are in. Most of the water I am in is pretty debris free, so I could probably get a non strainer and be fine, but in some places there is a constant barrage of small twigs you don't want tearing the pumps up or ending in the sacks.

jason@wakemakers.com
10-04-2009, 08:11 PM
If you're using a 3/4" or 1" fitting (which is sufficient for almost all systems), then you really don't need to worry about a strainer.

What type of system are you planning on doing?

TallRedRider
10-04-2009, 09:59 PM
If you're using a 3/4" or 1" fitting (which is sufficient for almost all systems), then you really don't need to worry about a strainer.

What type of system are you planning on doing?

Jason,

Are you suggesting a 1 inch intake fitting would be OK for a 3 pump system?

jason@wakemakers.com
10-04-2009, 11:01 PM
There are lots of variables that go into determining what size intake is appropriate for a given system, so it's hard to make a blanket statement, BUT, a 1" intake will support a theoretical maximum of 3,500GPH, so if you're installing a system that uses Jabsco pumps (an assumption to be sure, but most Mastercraft owners do because that's what the factory uses), there is plenty of capacity available for three pump system that is correctly designed.

TallRedRider
10-05-2009, 01:09 AM
There are lots of variables that go into determining what size intake is appropriate for a given system, so it's hard to make a blanket statement, BUT, a 1" intake will support a theoretical maximum of 3,500GPH, so if you're installing a system that uses Jabsco pumps (an assumption to be sure, but most Mastercraft owners do because that's what the factory uses), there is plenty of capacity available for three pump system that is correctly designed.

The surface area of a 1 inch hose is about 0.785 inches (Pi R squared), but the surface area of 3 3/4 inch hoses is about 1.32 inches. So I suppose that you are right, but the flow would have to be about 40% faster through the 1 inch hose since the surface area is only about 60% of the surface area of the pump intakes. It is more complex than that, but for 'back of the envelope' kind of math it works. For that reason, I would go with a 1.5 inch intake, and that is what it appears that the engineers at MC thought also. The only way to make the water go faster is to create more suction pressure. I think a 1 inch hose would be slightly restrictive since the pumps would have to create a little more suction to pull the water through a 1 inch intake at a faster rate than it already goes.

If the intake had to travel a long distance, then it would magnify the problem. Over a short distance, there may not be any noticeable difference in flow.

kbob
10-05-2009, 05:36 PM
My plan is to have a 1500 lb fat seat with two 2000 gph pumps for in an out connected to a 1" line, and then maybe an integrated bow sac and a ski locker sack with a 1" line...maybe a 3/4"...not sure yet and might try to tee them into the existing bilge line. But i'd have separate aerator pumps connected to each fat sac. I can't deside on one or two thru hull fittings for the intake. I'll try to post up a diagram this week for clarity.

endl
10-05-2009, 06:32 PM
A manifold system is not a bad idea simply because a 1" line coming in is plenty big then you can come off the maifold to all your other points. Only 1 inbound below the water level is good then you can have 1 shut off point. Some of the other brands use low voltage sprinkler system valves and aerator pumps like you described. They work fine and are a little cheaper than going the Jabsco pump route. Creating a manifold out of PVC is simple. and can be put just about anywhere convient.

I personally like mine exiting throught the sides so I can see the guage and the side and know when its completly empty. The newer boats exit through the bottom.

kbob
10-06-2009, 12:00 PM
Ok here is a rough sketch in paint of my system so far for my '94 PS205. The green arrows are swing check valves and the red boxes are pumps. There are two 2000 gph pumps for the Fat Seat and probably T-1200's for the rest.http://i197.photobucket.com/albums/aa6/kdwall44/Ballast.jpg

TallRedRider
10-06-2009, 02:08 PM
A manifold system is not a bad idea simply because a 1" line coming in is plenty big then you can come off the maifold to all your other points. Only 1 inbound below the water level is good then you can have 1 shut off point. Some of the other brands use low voltage sprinkler system valves and aerator pumps like you described. They work fine and are a little cheaper than going the Jabsco pump route. Creating a manifold out of PVC is simple. and can be put just about anywhere convient.

I personally like mine exiting throught the sides so I can see the guage and the side and know when its completly empty. The newer boats exit through the bottom.

Kbob, I like your diagram.

I am going to stick with my guns on the size of the intake. The Tsunami T-1200's have a 1 1/8 intake on them, whereas the T-800's have 3/4 inch. The 3/4 inch is much easier to find connectors for, so you might consider those. I think there is a reason that Tsunami went with a bigger hose, and they are the ones who engineer the pumps. If you just go with one intake, you are going to be disappointed in a 1 inch intake for 3 pumps. 1 inch might work for how you have it drawn up, but IMHO, I would go bigger so that you don't end up doing it a second time when you realize how much flow restriction you have.

jason@wakemakers.com
10-06-2009, 04:02 PM
The surface area of a 1 inch hose is about 0.785 inches (Pi R squared), but the surface area of 3 3/4 inch hoses is about 1.32 inches. So I suppose that you are right, but the flow would have to be about 40% faster through the 1 inch hose since the surface area is only about 60% of the surface area of the pump intakes. It is more complex than that, but for 'back of the envelope' kind of math it works. For that reason, I would go with a 1.5 inch intake, and that is what it appears that the engineers at MC thought also. The only way to make the water go faster is to create more suction pressure. I think a 1 inch hose would be slightly restrictive since the pumps would have to create a little more suction to pull the water through a 1 inch intake at a faster rate than it already goes.

If the intake had to travel a long distance, then it would magnify the problem. Over a short distance, there may not be any noticeable difference in flow.
Like I said, there are lots of variables that go into determining what is the correct size intake (pump head, number of bends, type of fittings, number of pumps, etc.), so it's almost always possible to over engineer things. I won't make a guess as to why Mastercraft (and others) use 1.5" intakes, but the fact that the engine raw water supply uses the same size hole, fitting, ball valve, etc. is worth noting.

I'm actually in agreement with you that going to a larger thru-hull is good insurance that you won't have flow problems, but many of our customers want to know the absolute least they can get away with because the incremental cost for the intake, ball valve, hole saw, etc. starts to add up. Ultimately, based on our actual testing, for the amount of water that we're talking about (typically at the most 100 gallons/reservoir), there is almost no difference in fill speed given the variables we're discussing. If you were talking about moving an order of magnitude more water then the difference may become apparent.

My plan is to have a 1500 lb fat seat with two 2000 gph pumps for in an out connected to a 1" line, and then maybe an integrated bow sac and a ski locker sack with a 1" line...maybe a 3/4"...not sure yet and might try to tee them into the existing bilge line. But i'd have separate aerator pumps connected to each fat sac. I can't deside on one or two thru hull fittings for the intake. I'll try to post up a diagram this week for clarity.
I would recommend NOT Teeing into your bilge line. If you were only installing one bag and wanted to get away without drilling any new holes in the boat that may make sense, but given the size of your system, and the fact that you're comfortable drilling multiple holes, I would suggest installing a new dedicated thru-hull for each bag.

Ok here is a rough sketch in paint of my system so far for my '94 PS205. The green arrows are swing check valves and the red boxes are pumps. There are two 2000 gph pumps for the Fat Seat and probably T-1200's for the rest.
You may want to revisit your use of check valves; for your forward bags, they may not provide the functionality you're looking for.


I am going to stick with my guns on the size of the intake. The Tsunami T-1200's have a 1 1/8 intake on them, whereas the T-800's have 3/4 inch. The 3/4 inch is much easier to find connectors for, so you might consider those. I think there is a reason that Tsunami went with a bigger hose, and they are the ones who engineer the pumps. If you just go with one intake, you are going to be disappointed in a 1 inch intake for 3 pumps. 1 inch might work for how you have it drawn up, but IMHO, I would go bigger so that you don't end up doing it a second time when you realize how much flow restriction you have.
I agree on the intake issue, either install one that is large enough to feed the whole system, or go with an individual intake for each bag. There are pros and cons to each, but if you have the packaging space for manifold in the bilge (which can be hard in direct drive boats), go with the single intake, it will cost you less money and be less work to install.

T1200 vs. T800 is a hot debate, and again, there are pros and cons to each. You can use Fly High's W747 fitting to make integrating the T1200 MUCH easier if you ultimately decide to go that route. For many people, the extra cost of the T1200 (pump, fitting, hose, thru-hulls, it all adds up), isn't worth the relatively small increase in speed they realize.

brucemac
10-06-2009, 04:14 PM
been following this thread. what is/are the disadvantages of using a larger single intake? is it simply a matter of cost adding up downstream or are there other concerns?

TallRedRider
10-06-2009, 04:32 PM
been following this thread. what is/are the disadvantages of using a larger single intake? is it simply a matter of cost adding up downstream or are there other concerns?

I am obviously on the side of the bigger intake. The cost of the intake is a little more, but we are not talking big numbers here, extra $20. A short segment of bigger hose, a few extra bucks. The only other disadvantage of a bigger intake I can think of is in the event of a catastrophic failure. The boat will fill with water faster if you have a 1.5 inch breech in the hull vs a 1 inch breech. If you have 2 bilge pumps, you might even be able to come close to keeping up with a 1 inch hole, but a 1.5 inch hole will overpower you quickly.

All through hulls should be immediately mounted to a shut off valve for quick shut off in the event of a failure.

Jason, thanks for your insights. I appreciate hearing your experience. I am unsure of the size of the through hull for the engine impeller...you are saying it is just 1 inch? I noticed when wakeboarding that there is an incredible volume of water flowing through it when the boat is going.

kbob
10-06-2009, 04:57 PM
I appreciate all the thoughts, and I am open to all suggestions because i'd like to do it as well as i can the first time around. I've seen several posts on here as well as WakeWorld where guys have added thru hull fittings under the floor between the motor and the gas tank on their direct drives close to the shaft. With that set up, I don't see how they could quickly access their shut off valves.

Also...where would be a better place to put my check valves?

brucemac
10-06-2009, 05:17 PM
jason, pm at ya.

jason@wakemakers.com
10-07-2009, 01:00 PM
been following this thread. what is/are the disadvantages of using a larger single intake? is it simply a matter of cost adding up downstream or are there other concerns?
Practically speaking, the disadvantage is increased cost. Larger intake, larger ball valve, larger hose, it adds up to at least $50. If you're on a budget, you may be trying to save money wherever you can.

All through hulls should be immediately mounted to a shut off valve for quick shut off in the event of a failure.
This is paramount!

Jason, thanks for your insights. I appreciate hearing your experience. I am unsure of the size of the through hull for the engine impeller...you are saying it is just 1 inch? I noticed when wakeboarding that there is an incredible volume of water flowing through it when the boat is going.
At the end of the day, I don't propose to be an expert here, but we have done one or two systems, so I have a little experience. ;)

I was implying that the raw water intake is 1.5", so from Mastercraft's standpoint I can see where it would be advantageous to have only one size intake and one size drill bit to speed up rigging and reduce the number of mistakes that are made. I'm not in any way suggesting that I have any knowledge or information to support that theory, but if I was Mastercraft and looking to optimize production and reduce costs, that's something I would look at.

I appreciate all the thoughts, and I am open to all suggestions because i'd like to do it as well as i can the first time around. I've seen several posts on here as well as WakeWorld where guys have added thru hull fittings under the floor between the motor and the gas tank on their direct drives close to the shaft. With that set up, I don't see how they could quickly access their shut off valves.

Also...where would be a better place to put my check valves?
For direct drive boats it usually makes the most sense to have the intake installed on the opposite side of the raw water intake for the engine. That's far enough back in the boat that you will always have water, even when surfing, and it's far enough forward that you can easily access the ball valve if you need to. Also, that should be behind the paddle wheel if you have one, so you won't effect it's functionality.

I was suggesting that you revisit using check valve at all. They will work for your rear bag no problem because that typically drains at speed, but bags up front typically fill at speed, which a check valve can't prevent. To stop that you need to use a vented loop. PM if you want more info.

jason, pm at ya.
Back at you, let me know if I can help.