External hull mounted water pickup for a triple outboard cat

[Garmin]

<HR SIZE=1><!-- / icon and title --><!-- message --><!-- google_ad_section_start -->I am rigging a 35 Motion with triple outboards. Are hull mounted external water pickups necessary, particularly for the center engine? i have one thing worrying me. the current location of the pickups on the sponsons is directly in the line of the bullet of the Sportmaster gearcases, would that be a problem? how do i go about this?

[1fastg3]

Talk to Mr. Demeanor on the borad He Just did one ...<!-- BEGIN TEMPLATE: postbit_onlinestatus -->

[Mr. Demeanor]

Your not going to find much info out there. Heres the thread I started when I began the project. I still dont have any hard data other than I have good pressure at any speed but have only run it to about 75mph so far. Its a very different setup than you have...about 1/3 scale.
http://www.screamandfly.com/showthre...p&daysprune=14

[Shaun Torrente]

The only hull mounted pickup that works well without hurting performance because of drag is thru-hull style... problem is they are very finicky and hard to get just right... i expiramented when i had my 24 with every transom style mounted pickup you could think of.... Whe i had good pressure i lost as much as 9 mph... When i would grind it down where it was not hurting performance i would lose pressure.... You should not need it on your triple setup, notch the sponsons and the center motor will do fine

Shaun

[Brad Zastrow]

It is not necessary but you will need to run the engines low enough to maintain water pressure. That will cost you a few mph. Personally I like the extra protection the low water pickups give you. Losing an engine to low water pressure happens fast. On a big cat like your Motion when making a turn you could lose water pressure on one engine without pickups. I used two water pickups on my triple Motion. I do not remember how we split the plumbing. But the best way to rig it is to use both the lower units and the lower water pickups with one way check valves. I believe we installed the water pickups in the lowest part of the sponson that kept them out of the water flow of the bullet of the lower unit.

[Shaun Torrente]

Brad,

You are correct about having to run the motors a touch lower, but it has been my experience that on a pleasure boat you lose less doing that than running transom mounted pickups... Also you made a good point about losing pressure when turning, what we have done with the race boats and i now started doing on the pleasure boats is to run a stabilizer hose between the motors, because when you turn one motor picks up a bunch of pressure and the other loses a bunch, so with a stabilizer hose between the motors it solves that problem

Shaun

[Brad Zastrow]

I found a photo of my 35 Motion. Notice the water pickup at the lowest part of the sponson. That is where the drain plug would normally go. Use the location and make a new drain plug further out. Notice the vents in the top of the notch. Those have long hoses that go up above the water line to help the boat plane off much, much faster. Day and night difference.



Here is a 35 Motion with quad setup with the water pickup in the same location.

[Brad Zastrow]

I like the stabilizer idea. The loss of water pressure while turning cost me an engine. After that I added the low water pickups. Another good idea is use ramps in the bottom of the hull directing water to the lower unit pickups. I have only seen that recently and have no pictures. Anybody have some to post?

[Adam McKeon]

Give Hardin Marine a call 1-877-900-7278, they will have what you need. Pick ups, high capacity strainer, ect ect. And the ventilation tubes help tremendously.

[BUZZIN' DOZEN]

[Brad Zastrow]

Shaun, do you use some sort of check valves on the stabilizer hose? I am assuming if only one engine is running at idle it may cause problems? How do you plumb this setup?

[Mr. Demeanor]

Shan thats a huge drop in speed. Not doubting you but wow! I only have 3/16" exposed and have 20psi. I did run the boat to 80mph with the pickup 1/2" down but not plumbed to the engine. Just wanted to see if it effected speed and it went right to 80.5mph before I had to get out of it. I dont think it going to hurt and on mine, getting the lower unit up further has to reduce drag more than the little scoop cold increase it.
Did you try putting a ramp in front of the transom mounted pickup? I am thinking about doing that just to get the pickup even higher and out of the path of debris.
This is how mine is now. The white plastic is there to show how it fits against the transom. And yes, I know we are talking about completely different animals!

[Mr. Demeanor]

Slightly off topic...
Brad, my center console and a lot of others have similar issues with suction under the notch or engine bracket. A lot of the builders use through hulls like yours to vent the area but are much bigger. Fountain used half round tunnels under the notch on mine to vent. I also get better hole shot by leaving the fishbox drain seacock open which vents to the same area. You can hear the air being sucked out of the forward fishbox.

Pic also shows the transom mounted water pickup for the livewell which will fill the 50 gallon livewell quickly with the pump off at speed. Make for a clean install. They make one with an adjsutable tube and I bet you could mount it right through where a drain plug was mounted.

[STV_Keith]

Not the same setup as you, but I have gone to supplemental water pickups on my Scarab. I run Johnson V8's with Merc V6 gearcases and they just don't move the volume of water at idle that the V8 cases did. I installed pickups through my trim tabs, go in to a 29GPM pump (free flow), then up to the exhaust adapters into the cold water stream with a check valve to keep the water from coming back out if the gearcase made more pressure than the pump/pickup. Here's a few pics...

[Shaun Torrente]

Shaun, do you use some sort of check valves on the stabilizer hose? I am assuming if only one engine is running at idle it may cause problems? How do you plumb this setup?

What i do on a pleasure boat, especially one in salt water is put a ball valve between the 2 motors, when i am testing or flushing i have the ball valve in the off position (stopping flow between the 2 motors) because you are right with only one motor running it will dump out the other... The other reason i turn it off when testing is so that i can dial in the ramps an engine hieght properly on each motor without the stabilizer affecting my pressure reading.... To me the ramp is a must and will allow you to run plenty of engine height, but the ramp also causes pressure drop to be worse when turning because the motor pickups move out of that stream created by the ramp.... After the boat is dialed in i only turn the valve off for flushing (not an issue for you freshwater guys).... Parking and short periods around docks and such don't give you enough time to worry about overheating... It is also good to have the valve in case of a breakdown and you have to get home on one motor... On a triple setup i would run 2 valves....

Demeanor,

Every application is different it might not hurt you as much, my testing was done with 2 3/4" square pickups, one on each sponson hanging 3/8" below the bottom... I could not believe how it effected the boat... I started out with a 9 mph loss but 25+psi (without the pickups i had 8psi).... Came back to the trailer and ground them to 1/4" below and now lost only 6mph and pressure dropped to 14-16 psi.... Came back in ground it to about an 1/8" and still lost 4 mph and water pressure was about 12psi.... ground them level and lost no speed but had no extra pressure.... Lowered the motors an 1/8" had 12 psi and only lost 1mph ..... Later on i put the ramps and was able raise the motors an extra 1/4" during the winter and bested my speed by 2mph

Shaun