I have recently changed out a stock set of iron heads to Ederlbrock aluminum marine heads on a 502MPI. I have done some research and would like to know who sells a closed cooling system kit for this motor? We spend more time in brackish-to-salt water here around the Gulf of Mexico and concerned with corrosion in the heads. The heads are anodized with Cometic head gskt but still not confident that is enough? I do have the Mercathode working......

I am a firm believer in closed cooling. I would recommend a system from Monitor Products.. I have used them before with success.

http://www.monitorpro.com/

Man, after looking at the kits that cost $800+, it seems like someone with some decent mechanical aptitude could put together their own system at a fraction of the cost. I have a buddy who works for an outfit that does a lot of stainless steel welding and fabricating, and this has the wheels turning for me.

http://www.offshoreonly.com/forums/g...ng-system.html

Not sure if you saw this when the thread was active, but the above link will get to a thread I started a short time ago. Its regarding a pair if 575's I built this winter. I had to fabricate a closed cooling system for these engines. I only wish I could have bought a pre made kit for $800 and be done. It must have cost nearly that much in parts anyway, not to mention the hours and hours it took me to make everything. If you are lucky enough to find a kit for your engine, buy it and just bolt it on...

Looks like the blower complicated that installation considerably. I'm thinking that my NA installation should be a lot simpler, but I'm sure there are several "gotchas" that I'm not seeing. Still, the concept is so simple that it's surprising that Merc didn't equip their motors with this from the outset, especially the expensive blue motors.

I was thinking of doing the same thing but I shelled out about $1,200 and got the monitor system...... I picked it up from the factory as I live in Tampa and I am very happy with it. I talked with some of the people there and they do a ripping business supplying systems for OEM manufacturers namely Yanmar. There facility was cranking out stuff like you would not believe! I have been taking it easy so far with my new NA 502 and so far I have not exceeded 4,000rpm and the water temp has not even got above 170 yet...... I have aluminum heads, intake and exhaust and needed to go closed cooling here in the salt water. I did think about getting a used system and making it myself but having a proven setup that will work at my horsepower level with a warranty as well made the decision easy........ TBF

TBF, did you go with the full system that includes the exhaust, or just the block and heads? I might add the block system as a future upgrade to mine, since I am running the AFR aluminum heads (non-adonized) and aluminum intake. I am running in fresh water, which will help, but I will get in the habit of pulling my block plugs after running it just in case.

Speaking of block plugs, has anyone ever tried just plumbing some fittings leading up to some ball valves instead of the plugs? It would make it real easy to drain the block without worrying about dropping the plugs in the bilge, but I could also see it getting blocked with silt.

I have the full system as I am using aluminum 496 Exhaust..... I did have them ceramic coated inside and out but I need all the help I can get being in salt water! I have stainless risers and they of course see the exhaust sea water from the heat exchanger but they should last a long time as I fresh water flush after every use with salt away as well...... I would say the half system would be fine for you if you are always in fresh water. Having anti-freeze and the corrosion protection in your block all the time has got to be a bonus.......

Also, I forgot to mention that did you say you were going to drain the lock after each use? I would say that is a bad idea as rust and corrosion will really get bad when all that air hits the wet cast iron....... Keep the water in the block as oxygen is what is the real culprit that causes all the rust......