dual water supply

K

KEVIN D TOBIN

Member
Jun 12, 2018
69
Boat Info
1993 290 sundancer, 7.4L mercruiser repower 2018
Engines
7.4L Bravo ll drive
I want to add a thru-transom watersupply but as mercury has advised me to keep the one that goes thru the outdrive, because it cools the outdrive. has anyone had any experience with this plumbing, I mean can I just come off the back of the transom exsisting supply and tee in at the thru-transom fitting then go thru a strainer then to the pump ? This will all be 1.25" id hose
 
Install a thru-hull pickup (bottom of the hull) with a seacock on the inside. Then to the strainer. Then to the raw water pump. Cut the drive hose before it goes through the transom and install a block-off kit. This way you'll have water constantly flowing through the drive but you won't have to worry about it getting clogged where it goes through the transom and eventually stopping the flow.
 
Lazy Daze said:
Install a thru-hull pickup (bottom of the hull) with a seacock on the inside. Then to the strainer. Then to the raw water pump. Cut the drive hose before it goes through the transom and install a block-off kit. This way you'll have water constantly flowing through the drive but you won't have to worry about it getting clogged where it goes through the transom and eventually stopping the flow.
Click to expand...
how will water go thru the drive if you are cutting off the suction from the pump ?
 
KEVIN D TOBIN said:
how will water go thru the drive if you are cutting off the suction from the pump ?
Click to expand...
I’m not sure of this question, but the thru hill pick up described above is how my 270 came from the factory. So, it can be done.

You definitely don’t want to go via the transom. You want get enough water flow that way. A scoop strainer pickup on the bottom will help push water the to engine at speed.
 
The dual pickups are nice, particularly if you trailer or use a rack. I had a thru hull but installed dual pickups so that I could use the muffs on the trailer. They are far easier to use than the fake a lake. Also, you don’t have to worry that the seacock is open.
 
b_arrington said:
I’m not sure of this question, but the thru hill pick up described above is how my 270 came from the factory. So, it can be done.

You definitely don’t want to go via the transom. You want get enough water flow that way. A scoop strainer pickup on the bottom will help push water the to engine at speed.
Click to expand...
Why don't you want to go thru the transom ? Mostly all high speed boats use this method . I don't want to loose anymore floor space to be able to move around in that bilge, if you are running with the transom supply blocked off which is what I wanted to do but mercruiser advised not to because it will make your outdrive run hotter, and the research I've read says the same thing. The advantage of running a thru-tranmsom is less chance of sucking up sand and wantnots, type in on google "thru-transom water pickup" and you will see what I'm talking about. Here is mercruiser #920-929-5040, call them and ask why yours came from the factory that way. Good talking to you thou.
 
KEVIN D TOBIN said:
If it doesn't have a place to go there won't be any flow
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Sure it will. Up above I mentioned cutting the hose - the hose end will now be open. The block-off kit is for the hole in the transom. This isn't anything new - this kind of thing has been done many, many times before... very succesfully. Lot's and LOT'S of boats have it setup with a thru-hull ONLY. It's a tried and true method.
 
Lazy Daze said:
Sure it will. Up above I mentioned cutting the hose - the hose end will now be open. The block-off kit is for the hole in the transom. This isn't anything new - this kind of thing has been done many, many times before... very succesfully. Lot's and LOT'S of boats have it setup with a thru-hull ONLY. It's a tried and true method.
Click to expand...
OK I didn't see the part about cutting the hose, why wouldn't you want both ?
 
KEVIN D TOBIN said:
Why don't you want to go thru the transom ? Mostly all high speed boats use this method . I don't want to loose anymore floor space to be able to move around in that bilge, if you are running with the transom supply blocked off which is what I wanted to do but mercruiser advised not to because it will make your outdrive run hotter, and the research I've read says the same thing. The advantage of running a thru-tranmsom is less chance of sucking up sand and wantnots, type in on google "thru-transom water pickup" and you will see what I'm talking about. Here is mercruiser #920-929-5040, call them and ask why yours came from the factory that way. Good talking to you thou.
Click to expand...

I'm not really interested in talking to Mercury. It worked great from the Sea Ray factory, and I've since sold the boat.

Seems like you've decided on your solution, so further discussion seems unproductive.
 
ColoSR said:
The dual pickups are nice, particularly if you trailer or use a rack. I had a thru hull but installed dual pickups so that I could use the muffs on the trailer. They are far easier to use than the fake a lake. Also, you don’t have to worry that the seacock is open.
Click to expand...
you must of seen my boat on the trailer, the thru-hulls sit right on a bunk support
 
Your bunks should line up with your stringers, apparently yours don't. you'll need a toilet plunger style flusher unless you use another method from the bilge.
 
scoflaw said:
Your bunks should line up with your stringers, apparently yours don't. you'll need a toilet plunger style flusher unless you use another method from the bilge.
Click to expand...
 
the outside flange seems to ride a little on the support or maybe the boat isn't sitting perfectly center, this is the thru-hull for the waste water, it's 1.5" id . I have to replace the valve cause it won'T close. Does anyone use those overboard ports ? Cause I was thinking about using that one for my water pick up ?
 
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