PARADOX

Long story, short version. I had low water pressure on sensor some months ago. Not the sensor. Checked all hoses, OK. impeller is new. etc. So I bypassed the outdrive intake and did a temp, external water pick up. Water pressure is back, but it's actually higher then coming through the drive. I know with the speed. 50-60 MPH there is water forced into the tubs/ pipes but I'm getting 30-38 PSI at 4000+- RPM. Is this OK? with external pick ups? Apparently my low water issue is due to the hose or the 90 deg pipe in the drive and the transom. I know the damn part. I don't even want to mess with it so I'm thinking putting in external water pick ups but just want to make sure the pressure with them is in the normal range.
Thx
P

thirdchildhood

iTrader: (6)

With closed cooling it is OK. With raw water too high.

PARADOX

It's closed cooling, and 525's. EFI. I'm asking about the raw water (sea water) pressure.

Unlimited jd

iTrader: (5)

Is still try to get it lower. Not as detrimental as if it were open cooling but still not ideal. The high pressure could actually be a sign of the water backing up in the system and not getting out fast enough causing temps to rise. Again not as much of an issue with closed cooling but I'd rather see it around 20

PARADOX

With the bypass, external water pick up, temp is good. Both motors been running around 25-28 at higher RPM's with water from the outdrive. With this make shift by pass, and checked ALL the hoses, coolers, there is no restrictions. Temp is good with the bypass. Temp got to 165's when I had the water coming through the drive, so I know something was up. Merc.'s guess was that I have a leak and getting air in the system at that darn tube at the transom. They were right. I had air bubbles when I put in a plastic tube. With the bypass, everything is good but pressure is up.

HyFive578

iTrader: (3)

That pressure does seem a bit high. Maybe the external pickup is too wide and you are getting too much water volume compared to what comes in through the drive causing the higher pressure. If the pressure climbs too much you could start to see leakage at the seal in the sea water pump housing.

PARADOX

Good point. My temporary pick up, is 1" IS diam tube ( made a 45deg cut in it so yes, it an get a lot of water) into 1 1/4" rigid rubber tube into the impeller housing. Just like the outdrive system, but the 1" pick up might be too big. I know the drive little tube is smaller. (3/4" ? )

HyFive578

iTrader: (3)

I'm not sure of the exact size, but I'm pretty sure the water hose between the pickup holes in the drive and the fitting in the transom that the 1 1/4" hose connects to is less than 1" ID. I bet your pickup is just a little too big...

mike tkach

iTrader: (3)

the depth that the pickup enters into the water plays a big part in water pressure.can you raise the pickup one quarter inch?

PARADOX

Totally stumped on this one guys.
With the temp external pick ups pressure went up. may be a ted high, but it went up. So.. before I start drilling holes and install external pick ups as a permanent set up, I changed the drive inlet tubes from Port to Starboard. Thinking... if the issue is in the drive, then the Port drive should loose pressure. (Starboard was loosing prior) Sucking water from the Port drive (extended the intake hoses) Starboard pressure is still low. Port is OK. THus the outdrive hoses, etc are ok. All the engine hoses been removed and checked. Oil cooler; clean. Front heat exchanger; clean. Any thoughts why my water pressure could be low? HEEEEELP. Impeller is new. Rotation correct.