High Water Pressure 2.4 BP

**Little boat that could** · 08-06-2025, 11:00 PM

Can the restrictor size increase water psi or decrease. Running at 4500 rpm i have 15 to 20 psi on both motors anything above 5k and higher the water psi goes up as fast as the mph looks to max out the gauge.These are two fresh power heads one piece tuners 1/8 restrictors no poppet all new pans and gaskets updated part numbers from Mercury cross over hose from head to head cle big window four hole lowers.The only thing that i can think of that i could of changed was the size of the restrictor both motors are doing the same thing.Any help on this would be greatly appreciated. Thank You

**Carter Powell** · 08-06-2025, 11:15 PM

Is this the same gauge that you have had all along? 15-20 PSI at 4500 rpm is not bad. How high does it go?

Carter

**Little boat that could** · 08-06-2025, 11:24 PM

Same two gauges and they both max out its a twin engine and the only thing i could think of i never check the size of the restrictors

**David - WI** · 08-06-2025, 11:31 PM

The water pressure at the inlet on the lower unit does go up as fast as the mph... that's how the old speedometers work. If you don't have something (poppet) dumping water, the pressure in the motor goes up in proportion to your mph. I think the only thing you can do is open up the restrictors a bit, if the pressure bothers you.

**Little boat that could** · 08-06-2025, 11:44 PM

David the gauge is maxing out at 30 psi do you know what the max psi is allowed and thinking of opening the restrictor to 1/4

**skialot2** · 08-07-2025, 12:06 AM

I have stock cooling with poppet, two piece plate and thermostats on my 2000 2.5 200. I had 15 psi of water pressure at wide open with the stock fishing lower or a coned lower. But when I switched to a big window 4 hole CLE I now have 20 psi at wide open.

**David - WI** · 08-07-2025, 12:35 AM

I'm not sure, the gasket on the exhaust cover is probably the weak link?

**tlwjkw** · 08-07-2025, 06:47 AM

Originally Posted by Little boat that could

Can the restrictor size increase water psi or decrease.

stats, washers, hose from poppet cover??? which one? tha only one of that group would be tha from tha poppit cover.. one or two piece (with poppet) plate?...

**25two.stroke** · 08-07-2025, 05:10 PM

If I run my jack plate down too low I get high water pressure. 70-80 mph I can see 45-50 psi. If I bring it up to the edge of loosing pressure I can ride that line of 14-18 psi right where I want to be. If your engines are already at the correct height the best way to lower your pressure is to increase the dump out of the adapter plate. Either some of the dump holes are clogged with debris, someone plugged them, or you aren't taking water off of the poppet cover fitting. That 1/4 npt hole in the poppet cover should go to a 3/8 hose and out the cowl. You can also drill that pate out to put a bigger pipe fitting in it if you wish. Washer size only really changes how water flows in the head...

**Little boat that could** · 08-07-2025, 10:07 PM

one piece tuner with no poppet running 1/8 washers

**Onetime** · 08-07-2025, 10:42 PM

Bridgeport 2.4’s ran washers with a bigger hole. Going from memory it was at least 1/4”.

**tlwjkw** · 08-08-2025, 04:27 AM

tha bp's i remember had 1/8" washers, two 3/8's (or close to it) holes in tha adapter and a blank poppet cover.. we had ta "fine tune tha coolin' junk after tha fact... ANY high pressure (that amount is justa a judgement call by tha owner, we looked for minimum 10 lbs at max rpm) will be a restriction somewhere in tha system.... jmo.

**rjdubiel** · 08-08-2025, 08:14 AM

If these are stock BP with the stock adapter plates then they should have 4 small holes in the adapter plate to dump water into the mid section. Also you should have one hose off the heads, and one hose off the poppet cover dumping out the pan (no poppet in there, just the cover with a hose). When you had the powerheads off did you make sure all 4 holes in the adapter plate were open? You do have a dump off the poppet cover?

**tlwjkw** · 08-08-2025, 12:55 PM

i stand corrected.. tha 2.4's did have 4.. tha 2.5's had 2, but ya never knew what size they were gonna be from merc!

**25two.stroke** · 08-08-2025, 05:52 PM

Yeah all the 2.4 1 pc plates I ever saw had 4 little dump holes...like 3/16 of an inch or less. I usually open up the front 2 to about 5/16 and drill the back two near the exhaust to 1/4-20 and put cap screws in em with loctite...I never believed the 2.4 plates dumped enough without the poppet dump either. Something about hydrodynamics I don't think 4 small holes dump as much water as two bigger holes with the same cross sectional area. I ran a BP on a 2.5 plate with no poppet dump and big thermostat dumps (3/8") and always had perfect temps...for whatever that is worth.