there is some cheap coolers and exchangers out there. Thin areas and very poor brazing and even smashed tubes, I have seen on brand new units. examine what you buy inside and out.

What is the size of your unit and diameter and how many tubes are inside and how many passes does the flow make ?

Also did you mount a remote reservoir in conjunction with the heat exchanger - mounted at a high point ?

38in long by 5" dia...3 pass..3 stag raw water pump...water pressure at wide open...50lbs

Sorry yes remote..tank up high

I have the heat exchanger that came on a merc. 454 HO. It’s on a 625hp 540 now and I’m running a 140* thermostat. I boat in very warm water and my temps never exceed 150* at 30 psi at 5400 rpm. I don’t know how that translates to your 525 sci but for $200 you might give one a shot.

Anyone run the 5” merc exchanger with manifolds likes gils included (full system)?