525 cooling questions (2 issues)
 

Issue No. 1: I'm feeding more raw water out the starboard header vs the port one and the port one is running a lot hotter. I did a back flush and the header checks out. I noticed that the heat exchanger was the last thing in line before it gets routed to the headers. Is it possible for part of that to be clogged and to allow one exit into a header to pass more water than the other? Is there an easy way to check its internals or do I have to pull it and take the bolts off of each end? I was thinking about disconnecting the connections to the headers and firing the engine for about 20 or 30 seconds. The previous owner never used a sea strainer, but I put one on very shortly after buying the boat and I remember reading that some of the internals of heat exchangers can get clogged.

Issue 2: The boat was sold to me with a blown headgasket, but blown between an oil passage and a coolant passage. Hence it ran fine, but dumped a lot of oil into the coolant tank and water into the crankcase. The coolant tank was never properly cleaned and there still is some residual leftovers and it's tricking me into thinking I've got the same problem again. I'm pretty sure everything is ok though, but I need to get that tank clean to be sure, but it's chambered and hard to flush out. I need suggestions on how to get it clean and get all of the oil out of there. I really don't want to have to pull the right side header to take the tank off, but I will if I have to. Is there anything I can do while the tank is in there? Bleach??? or something else??? I am keeping a very close eye on it and my dipstick and peeking into the valve covers thru the fillholes looking for milk in the mean time. Just don't want a nasty coolant tank anymore and I don't want to pay what Merc wants for one.

Put some liquid Cascade in it. Run it for 15-20 mins. and cut it off. Then drain it and refill it.

Are you talking about the tank, or the whole cooling system?

The whole system. It will get rid of any oil residue left in there.

I was told about the drains on the bottom of the motor before. Where are they and what do they look like (brass etc...) How much coolant does it hold? Thx for the info.

My port headers do run hotter at idle than the starboard. They are cool to the touch after coming off plane though. Come to think of it my 496's did the same.