View Full Version : Closed cooling question about hose size

01-24-2013, 07:46 PM
I'm finally back on my 22 project and am dry-fitting the plumbing. I am using a full flow cooling system like what our man George Carter is using on his redhead.


Here's my question and a little background. On the OMC boats the raw water hoses that flow to both the power steering cooler and oil cooler are 1" I.D. The heat exchanger raw water intake calls for 1 1/4"id hose. My plan is to just put a coupler in and step the hose up from 1"to 1 1/4". The only other option is to replace the oil coolers with something that is set up for 1 1/4" water hose. ...still going to start at 1"coming off the water inlet hose coming off the transom mount. I guess I could also put a raw water thru hull in--- maybe even in tandem with the stern drive water inlet...

Does anyone know of have any thoughts if I will have either water volume or pressure problems if I just put a coupler in to make the connection? ...that's kind of my plan and if I need to make any changes then figure it out but thought I'd bounce it off of you guys here first.
Thanks, pics below:


01-25-2013, 05:06 PM
Hi Jay!
You've purchased the finest add-on closed system in existence, IMHO. Are you planning to keep the raw water pump in the outdrive? Is it the type of OMC that uses a drive mounted pump? If so, this may be your first decision. You might consider using a transom pickup for the raw water, if you do, you can remove the out-drive pump impeller. You can cap the the raw water inlet on the inside of the gimbal assembly. If you do this, also remove the hose that runs from the out-drive to the gimbal. Water will still flow through the out-drive for gear cooling purposes, but it simply dumps back into the water.
A Johnson crank driven pump makes a neat raw water pump installation. You can get them here;


for about $225.00 complete w/bracket.
So, my personal ideal system has a transom mounted pick-up (Stainless Marine http://www.stainlessmarine.com/?wpsc-product=1-n-p-t-male-1-14-o-d-s-s-transom-mount ), followed by the two coolers, and on the way to the Johnson crank mounted raw water pump.
It's easy to adapt the inlet 1" from the pick-up to 1-1/4" hose size.
The S-M pick-up supplies a tremendous amount pf water and I'm sure it would do well w/your coolers, after which the hose size could be increased to 1-1/4". Or, you can replace your coolers w/one of these http://www.ebay.com/itm/Revolution-Marine-Severe-Duty-Combo-Cooler-Assembly-/220343786399?pt=Boat_Parts_Accessories_Gear&hash=item334d835b9f&vxp=mtr which includes both oil and steering cooler and accomodates 1-1/4" hoses.

01-27-2013, 10:36 AM
As always, Thanks for your help George.