Good water flow/low water pressure

**dtmeeks** · 07-13-2019, 01:04 PM

I've got an 86 2.0 150 that I put on an 85 2.4 200 adapter plate. Same lower, same water pump, just ported the exhaust to match. Went from making 25 psi at idle to 10 and now it drops when I bring the rpm's up. Any insight on what's going on? I'm at a loss and have tried plumbing it every which way without pulling the power head.

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**dtmeeks** · 07-13-2019, 01:07 PM

Water pump has less than 2 hrs on it and made 20+ psi on old power head at idle. It has a ton of flow just no psi.

**Dave Strong** · 07-13-2019, 01:48 PM

If you made 20 at idle you had an issue before you did anything.

Dave

**Merc 2.5** · 07-13-2019, 02:20 PM

Originally Posted by Dave Strong

If you made 20 at idle you had an issue before you did anything.

Dave

I agree with this

**Jay Smith** · 07-13-2019, 03:24 PM

No Mercury should ever have over 18 lbs pressure at WOT you have a spent water blockage leaving the block or a bad gauge ...

Jayb

**half fast** · 07-13-2019, 03:29 PM

Sum ting Wong

**dtmeeks** · 07-13-2019, 06:12 PM

Gauge possibly but I don't think so. 2 4 was clean inside and had no blockage. New 2.0 is clean as well and nothing else has changed.

**Jay Smith** · 07-13-2019, 07:18 PM

Most of the time your blockage or restriction will NOT be in the engine it will be tuner adapter plates ...

Jay

**dtmeeks** · 07-13-2019, 07:32 PM

Adapter plates were clean as could be. I swapped mids and motor mounts at the same time so I got a good look. I had to open the exhaust port in the 2.4 to match the 2.0 but didnt touch anything else. Made sure the gasket matched too before I bolted it together but I'm wondering if there is a difference in water channels

**Dave Strong** · 07-13-2019, 07:50 PM

Originally Posted by dtmeeks

Adapter plates were clean as could be. I swapped mids and motor mounts at the same time so I got a good look. I had to open the exhaust port in the 2.4 to match the 2.0 but didnt touch anything else. Made sure the gasket matched too before I bolted it together but I'm wondering if there is a difference in water channels

Might be a difference in dump hole size.

Dave

**dtmeeks** · 07-14-2019, 03:35 AM

Originally Posted by Dave Strong

Might be a difference in dump hole size.

Dave

It seems that way but it's the same water pump, same water tube, and same 2 peice plate. You would think psi should be closer to where it was. I did go from a 2.4 clamshell cowl to a 2.5 cowl with a pan so I added some height and now wondering if there isn't a good seal on the water tube.

**tlwjkw** · 07-14-2019, 05:02 AM

did you change tha gasket between tha two plates?.. thats what wrong gasket there will do..

**dtmeeks** · 07-14-2019, 06:08 AM

Originally Posted by tlwjkw

did you change tha gasket between tha two plates?.. thats what wrong gasket there will do..

When I separated it the old one tore so I replaced it. It appeared to match but I'm wonderin if there were maybe some differences in hole sizes I didn't catch. I'm honestly thinking about going to a 1 piece plate and modifying it so I can control the flow.