Raw water wash down install

[BryceWCP]

Hi guys. Just purchased a raw water wash down kit. The plan is to plumb it to the existing thru hull that is in place for the fresh water pickup to the mercruiser impeller. Has anyone done this or can think of any issues with that setup? Possible flow restriction to the motor? Possible damage to the wash down pump while on plane? I don’t think there would be any issues but stranger things have happened.

Thanks in advance
Bryce

 

[gungadin]

I don't know how much or how fast the mercruiser raw water pump is able pull water from the ocean, but I would think that it would also attempt to pull whatever is in the line to and out of the washdown pump. This may or may not cause problems for the mercruiser pump especially if it involves air. Imo you could either install a shut off valve in the line you "T" off the raw water pump or run a dedicated circuit. Their may be ways to install the washdown system without using a thru hull that is below the waterline

 

[BryceWCP]

I don't know how much or how fast the mercruiser raw water pump is able pull water from the ocean, but I would think that it would also attempt to pull whatever is in the line to and out of the washdown pump. This may or may not cause problems for the mercruiser pump especially if it involves air. Imo you could either install a shut off valve in the line you "T" off the raw water pump or run a dedicated circuit. Their may be ways to install the washdown system without using a thru hull that is below the waterline

I see they do make in line check valves. Maybe a check valve right after the “t” going to the raw water pump.

 

[ship happens]

Put a separate thruhull fitting and ball valve for the washdown. Dont attempt to combine the 2.

Aluminum boat.. need to weld in an aluminum pipe with pipe threaded ends. Ball valve on that. Or go with plastic thruhull.

Fiberglass hull, bronze thruhull with ball valve. Make sure you run a ground wire to this assembly


Have fun

 

[Foxsea]

https://www.sportfishingbc.com/forum/index.php?threads/feeding-raw-water-washdown-pump.57370/

I agree with Ship: an additional through hull is the way to go. You do not want to pull water away from the cooling system. If you have a head intake that would be a better place to tee in if you decide to go with a tee. Definitely use high quality components for through hull and sea ****. Install a well-bedded backing plate for the installation.

 

[BryceWCP]

Thanks guys seems like that’s the consensus I’m finding. Will look into adding a thru hull. Seems like a more intimidating job than it actually is.

 

[gungadin]

If your raw water pump is capable of self priming, it is possible to install a thru hull well above the water line, if having one below the water line is of concern to you. It does need to be installed at the transom though. You need a thru hull of the appropriate size, one that you can use a pipe tap to thread the part of the thru hull that will sit on the outside to 1/2 or 3/4 in npt. you then thread a street elbow into that and run a plastic pipe down it to just above the edge of the transom, so it is above the water flow when on a plane. This allows you to use the washdown when trolling or stopped.
One thing I neglected to mention though. If you mount the wasdown pump below the level of the thru hull, there is the possibility of syphoning, especially if you use the pump and then don't break the syphon bu getting up on plane. Install a shut off valve or use a quick connector.

 

[profisher]

My thru hull for my wash down has the ball valve right on the thru hull fitting. I added a tee ball ball above the water line, between the thru hull and the pump. (my pump is mounted well above the water line as well) I have a 4 ft hose attached to the tee valve that allows me to turn the valve and use the 4 ft section to draw fresh water from a bucket sitting on the deck. After a days use I fill the bucket with fresh water, turn the valve, switch on the pump and flush the salt water out with the fresh.....extending the life of the pump.

 

[BryceWCP]

Alright guys. Going to attempt this install myself. Did some research looks like I’ll be using epoxy to mount the backing plate to the hull. From what I’ve read the thru-hull mushroom and seacock are then sealed using 3M 5200 (usually). At the local marine store today they did not have the 5200 only sikaflex. The store worker says that they always just use the sikaflex but sikaflex stays slightly soft in comparison to the 5200 witch cures hard. I’m leaning towards the 5200 as this is a fitting through the bottom of my hull and it’s most likely not coming off once it’s in there. Any reason to say use the sikaflex vs the 5200??

Thanks guys
Bryce

 

[bigbruce]

Alright guys. Going to attempt this install myself. Did some research looks like I’ll be using epoxy to mount the backing plate to the hull. From what I’ve read the thru-hull mushroom and seacock are then sealed using 3M 5200 (usually). At the local marine store today they did not have the 5200 only sikaflex. The store worker says that they always just use the sikaflex but sikaflex stays slightly soft in comparison to the 5200 witch cures hard. I’m leaning towards the 5200 as this is a fitting through the bottom of my hull and it’s most likely not coming off once it’s in there. Any reason to say use the sikaflex vs the 5200??

Thanks guys
Bryce

“Most likely” is the key. If you use 5200, you’ll never get it off. If there’s even a remote reason you’ll want to take it off, use 4200. Almost the same adhesion/sealing ability but not so permanent. I used 4200 to seal around my thru Hull transducer.

 

[ship happens]

I always use 5200 for below the water line permanent mounting. It doesnt dry hard. Just alot denser and alot more of a permanent material.


5200 will come off. We heat it up and it comes off no problem.

 

[dance a jig]

make sure the hose line from the seacock/shutoff valve leading to the pump is rated for such use, otherwise if you have seacock open and hose between it and pump fail, you better have a bilge pump that can keep up. good luck. DAJ

 

[bigbruce]

I always use 5200 for below the water line permanent mounting. It doesnt dry hard. Just alot denser and alot more of a permanent material.


5200 will come off. We heat it up and it comes off no problem.

I stand (or sit) corrected...

 

[ship happens]

I went away from using regular clear braided water line. I personally like to use the suction line. Its clear and has a blue coil stripe, some have a grey stripe depending on manufacturer. It does not kink, and holds up forever pretty much. It's the cats meow

 

[BryceWCP]

“Most likely” is the key. If you use 5200, you’ll never get it off. If there’s even a remote reason you’ll want to take it off, use 4200. Almost the same adhesion/sealing ability but not so permanent. I used 4200 to seal around

I went away from using regular clear braided water line. I personally like to use the suction line. Its clear and has a blue coil stripe, some have a grey stripe depending on manufacturer. It does not kink, and holds up forever pretty much. It's the cats meow

Thanks! I think I’m going go to with 5200 and I’ll look into that type of hose!

 

[Sandpiper]

Hey Bryce, Just incase you need some installation information from a guy that overbuilds everything on his boat.

Replacing Thru-Hulls and Seacocks - Marine How To

Tip: If you would like a higher resolution or larger photo simply click on the picture and it will get bigger. A Poor Idea The picture on the left is what not to do if starting from scratch and installing new seacocks.

marinehowto.com

 

[BryceWCP]

Hey Bryce, Just incase you need some installation information from a guy that overbuilds everything on his boat.

Replacing Thru-Hulls and Seacocks - Marine How To

Tip: If you would like a higher resolution or larger photo simply click on the picture and it will get bigger. A Poor Idea The picture on the left is what not to do if starting from scratch and installing new seacocks.

marinehowto.com

I like overbuilt. Thanks will give that a read probably a few times before starting this project!

 

[Aces]

For my set up I just ran a suction pick up off the back off my pod to the pump in the transom. Works great and I don’t have any thru hull fittings at all, filled them all in.

 

[dance a jig]

for your raw water intake hose between thru-hull/seacock and the pump, you want a hose specifically rated for "below water line". You will likely need a sawzall to cut the hose because it has so much reinforcement layers, which is there to protect you. something like https://tridentmarine.com/product/trident-silicon-rubber-heater-hose-132134-2/

 

[ship happens]

for your raw water intake hose between thru-hull/seacock and the pump, you want a hose specifically rated for "below water line". You will likely need a sawzall to cut the hose because it has so much reinforcement layers, which is there to protect you. something like https://tridentmarine.com/product/trident-silicon-rubber-heater-hose-132134-2/

That's hardwalled wet exhaust hose. Thats basically the most heavy duty hose you can buy. Awsome stuff