I'm adding a Imco 2" shorty to my single engine vee baja 272 next week but will have no time to test it before going to run long and hard at hot boat weekend at hardy dam. When going from a std pickup lower to a Imc-2 shorty what kind of water pressure increase have you guys typically seen? My boat will run just about 100 mph and I'm worried the water pressure will be off the scale high from other threads I faintly remember seeing a few yaers ago>. I currently have a water pressure gauge and I see between 15-20 psi in the high 90's. I do have a water relief valve that I bought a few years ago that is supposed to open softly after 14 psi if I remember correctly,I never installed it though because it hasn''t been needed yet.
If I do install it before going next week where should I tee it in? I'm running a crossover with no thermostat or circ pump,my raw water pump is a single stage kpm run dry if that makes a difference. I'm currently plumbed from otdrive to pump,thru fuel cooler,power steering cooler,oil cooler then to the engine,my innercooler is fed off water entering the engine at crossover. I was thinking thats where I want to tee in the relief valve but not 100% sure,Smitty

Pretty much everybody I know sees higher water pressure with Imco lowers.

Install the pressure relief valve somewhere after the oil cooler.

I saw a 10 PSI increase over a stock XR housing.
The first time I tested one, it blew my water pump housing apart.
I would also recommend plumbing the pressure relief valve after the oil cooler to maximize oil cooling. My through hull fitting is positioned so it dumps on the upper drive housing, hopefully cooling it some too.
Regards,
Steve

I think I saw about a 15 psi increase. It was enough to blow water hose off. I have my intercooler T'ed off right after the water pump. Then reliief valve is right before it goes in the engine. Have had no problems since installing valve.

Why not plumb at the sea strainer? Many come with a .5 or .75 NPT fitting. This might be a better project to do after your vacation.

I saw a decrease in pressure. Wreaked havoc with the guardian system on my 600sci. Trying to avoid an external pickup so have a few more tweaks to try. The pickup on the IMCO is a slot on the bottom. If you need a lot of trim to run like I do, that slot dissappears from the leading edge as you add trim. I had to do holes on the top side of the bullet to keep the ram effect w/trim. It's not a 100% dialed in but getting close.

I think my case is the exception, not the rule (oh joy!) so hopefully you won't have my issues.
good luck.

Didn't see any difference between XR with a low water pick-up nose cone and the Imco.

I had no ploblem with pressure . But they will suck up weeds around the dock big time ! I would put the pressure valve in the strainer. If you do not have strainers I would get them and save yourself a lot of head aches !!!!!!!!!!! been there done that ! Just my 02 cents Jeff

15 PSI, increase on mine...Plumed a set of Merc units just before the crossover.

I've had big time pressure issues with my 496 ho's after adding the IMCO's. the winterize dump valves can't hold back the pressure and it dumps into the bildge. also blew a hose a few years ago. I think last time i checked I was getting like 43 psi on scan tool, which is way too much. Been experimenting with a relief valve, but that doesn't seem to be working.