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JayZ
04-24-2014, 08:59 AM
For a variety of reasons i am converting my King Cobra setup to a crank mounted raw water pump.

it has closed cooling (like George's TR)

First question is how do i determine where to mount the transom pickup? ...also why not a thru-hull pickup?

Next question if a transom pickup do I run the risk of too much water pressure and maybe blowing off a raw water hose or injuring the heat exchanger etc?

Thanks,

Jay

gcarter
04-24-2014, 10:18 AM
Here's an example on Von Kamp's sharp keel 18.....
http://www.donzi.net/forums/showthread.php?49388-vonkamp-s-Barrel-Back-18/page2

And here's ditto on the TR.
http://www.donzi.net/forums/showthread.php?50476-Now-I-m-getting-serious/page42

I really like Stainless Marine pickups:
http://www.stainlessmarine.com/?wpsc-product=1-n-p-t-male-1-14-o-d-s-s-transom-mount
I've used this pickup several times w/very good results.

And here's the Johnson pump I like:
Johnson F6-B9 pump. It'll also need a stabilizer bracket (kept in stock).
http://www.marineexhaustmanifolds.com/raw-water-pumps.htm

The idea is to make a heavy paper template of the pickup mounting flange (I use a manila folder). I cut out all the holes and mark all the center lines. Then measure the distance from the pickup mounting flange bottom edge to the short edge of the pickup itself. The short edge of the pickup should be even w/the hull bottom, and the extended will be about 3/8" into the slip stream of the water flow. Locating the template requires some thought. you need to miss the gimbal castings inside and out. You also need to miss the stringers. You don't want to drill a hole into the endgrain of the stringers but it's a lot easier than it sounds. The inlet pipe is 1" SST pipe and I used a 1-3/8" hole saw to cut the hole. The important thing is to make sure your drill is perpendicular to the transom!!! :nilly:
I also like to saturate the wood around the large hole w/a thin penetrating epoxy like System Three "Clearcoat".
If you do it will never absorb water.

gcarter
04-24-2014, 10:42 AM
Through hull pickups will ultimately be offset to one side and will upset the handling (and probably slow you down if one or two MPH are that important).
Pressure isn't, or shouldn't be a problem. I mounted a mechanical pressure gauge pickup in the oil cooler drain port and a gauge in the dash. I also installed a 35# relief valve in the raw water supply line downstream of all the coolers. The valve goes overboard just in front of the bilge pump discharge.

I used this Johnson F6-B9 pump from J. A. Chamberlain who has the very best prices for these pumps. You'll also need to buy a stabilizer bracket for the pump and sized for your particular engine. I think they're about $25.00. They supply the same pump for both BBC's and SBC's. It's a very adequate pump.

JayZ
04-24-2014, 10:50 AM
Thanks George. ...so you recommend the relief valve i presume?

I was planning on using the surewood P105 pump since I found it locally locally. It is also stainless so might resist galling if i suck up any trash. (I do plan on using a strainer.)




Through hull pickups will ultimately be offset to one side and will upset the handling (and probably slow you down if one or two MPH are that important).
Pressure isn't, or shouldn't be a problem a problem. I mounted a mechanical pressure gauge pickup in the oil cooler drain port and a gauge in the dash. I also installed a 35# relief valve in the raw water supply line downstream of all the coolers. The valve goes overboard just in front of the bilge pump discharge.

I used this Johnson F6-B9 pump from J. A. Chamberlain who has the very best prices for these pumps. You'll also need to buy a stabilizer bracket for the pump and sized for your particular engine. I think they're about $25.00. They supply the same pump for both BBC's and SBC's. It's a very adequate pump.

JayZ
04-24-2014, 11:00 AM
Just for the record (and i should probably start another thread on this)

My power steering actuator appears to be leaking fluid. I have decided not to spend the $400-$700 I have been quoted for another obsolete OMC piece of hardware. Instead I think i will go ahead and start planning on converting to full hydraulic steering with external rams.

in order to do this on the King I plan on taking off the raw water pump from the back of the drive and putting some studs into the back of the drive to mount a machine shop fabricated bracket for the ram.

...stay tuned.

jZ

gcarter
04-24-2014, 11:05 AM
Thanks George. ...so you recommend the relief valve i presume?

I was planning on using the surewood P105 pump since I found it locally locally. It is also stainless so might resist galling if i suck up any trash. (I do plan on using a strainer.)

I didn't use a relief valve on the Minx, but it was only capable of about 65 MPH. It may be a good idea if you're looking for some bigger numbers.
Brand of pump doesn't matter to me. Chamberlain just has the best prices I've seen.
I also really like a hard mounted ball valve inside the transom. It's fail proof way of guaranteeing your boat won't sink!

JayZ
04-24-2014, 11:46 AM
I didn't use a relief valve on the Minx, but it was only capable of about 65 MPH. It may be a good idea if you're looking for some bigger numbers.
Brand of pump doesn't matter to me. Chamberlain just has the best prices I've seen.
I also really like a hard mounted ball valve inside the transom. It's fail proof way of guaranteeing your boat won't sink!


You forget I am first and foremost a sailboat guy and have an offshore sailboat. There will be a proper seacock (ball valve) installed.

Fishermanjm
04-24-2014, 09:10 PM
do the crank mount pumps work better that the belt driven pumps?

gcarter
04-24-2014, 10:22 PM
do the crank mount pumps work better that the belt driven pumps?

1. No belt to fail.
2. Very easy to change the impeller.
3. ya don't have to climb under the engine to remove the Merc pump.

Other than that, they're pretty much the same.

pipnit
04-26-2014, 09:23 AM
A couple years back when I did a bunch of work to the "Orange Whip," I used the stainless marine transom mount pickup. I then put a fitting, long tube on the motor and taped the guage to the dash and went out to see what pressure she would run. I think I was told not to exceed 15psi or you might start to shred head gaskets. So, I had to take the boat in and out of the water many times, carefully using a grinder to trim off the edge that went past the hull until I got to the numbers I was happy with.

gcarter
04-26-2014, 10:35 AM
A couple years back when I did a bunch of work to the "Orange Whip," I used the stainless marine transom mount pickup. I then put a fitting, long tube on the motor and taped the guage to the dash and went out to see what pressure she would run. I think I was told not to exceed 15psi or you might start to shred head gaskets. So, I had to take the boat in and out of the water many times, carefully using a grinder to trim off the edge that went past the hull until I got to the numbers I was happy with.

Thanks for that response! That's important on a raw water cooled boat! :yes:
But for heat exchanger cooled, the real limiting factor (I think) is the strength of the hoses. They really weren't designed for say 35-80 PSI.
The formula for ram pressure (Speedometer pitot pressure) is V squared X .0147= PSI. V is speed in statute MPH, thus, water pressure at 30 MPH = 13.23 PSI. 100 MPH = 147 PSI. The same could hold true (or close to the same) for cooling water pickups.

JayZ
05-10-2014, 10:31 AM
Going for a test run today with transom pickup and crank pump.

Plumbed to strainer, coolers first then pump.

Will be monitoring water pressure before pump.

How much is too much to come through coolers and hoses?

Thanks!

gcarter
05-10-2014, 10:41 AM
As stated previously, I think the limiting factor is the strength of the hoses.
I would be concerned w/pressure over about 35-40 PSI. Particularly
w/molded hoses. Obviously wire reinforced water/exhaust hose will stand more.
I once thought about a bypass around the raw water pump so max flow would
be available to the exchanger, but that's probably a bad idea.
I believe a relief valve is a better solution (if necessary).
Good luck w/your trial.

Conquistador_del_mar
05-10-2014, 02:54 PM
Going for a test run today with transom pickup and crank pump.

Plumbed to strainer, coolers first then pump.

Will be monitoring water pressure before pump.

How much is too much to come through coolers and hoses?

Thanks!

I just bought a 23' Warlock which is the first boat I ever had with a water pressure gauge. After reviewing a video I made, it looks like it reached 18-20lbs at WOT or 4900RPMs at 70+MPH. I don't know what would be acceptable PSI limits, but I thought I would post my results. Good luck on your first run :yes: