Mercruiser 165 Closed Cooling Conversion

[dhayes]

I have a strange question. I'm new to Mercruiser I\O's but I recently purchased a boat with a Mercruiser 165 inline 6. I'd like to convert it to a closed cooling system. I've done a little looking around at the various configurations and the 470 parts look like they will fit the larger 165 manifold.
A buddy of mine has a coolant tank, thermastat housing, and a 4" heat exchanger from a 470 (if I can make them work I can do it CHEAP). The main difference I've found between the two is the 470 includes the manifold in the closed loop so the location of the raw water introduction into the exhaust is back at the riser rather than at the front of the manifold. Do you know of any other differences or problems that I need to look out for? Is the heat exchanger big enough to work on the 6 cyl? I know it will take a different gasket at the riser but the rest of it seems to be a workable scenario. Have any of you ever seen this done successfully?

 

[JustJason]

Re: Mercruiser 165 Closed Cooling Conversion

To indirectly answer your question. It is generally a bad idea to put closed cooling on a motor more than a couple of years old. The openings on the inside of the heat exchanger are fairly small and with all of the years of rust and scaling inside of your engine, the exchanger will clog quickly and will clog often even after cleaning it out. Your best bet is to keep the raw water setup. You don't want to be overheating 3 times a month when your out on the water.

 

[ziggy]

Re: Mercruiser 165 Closed Cooling Conversion

and with all of the years of rust and scaling inside of your engine

i've had to empty my block and manifold 3 or four times now this spring for over night lows below freezing. ea. time i did it. i had to ream out the rust scale from the manifold before it'd start to drain. i catch the water in a coffee can so i can see what came out. i'm getting a little less the 3rd or 4th time. but still. maybe a half thimble full? certainly enough to plug the drain hole...
everything i've ever read, confirms what jj is saying. i wouldn't consider it on my L6 for reasons he's saying...

 

[Bondo]

Re: Mercruiser 165 Closed Cooling Conversion

I'd like to convert it to a closed cooling system.

Ayuh,... Several years ago(4-6), FreebeTony did the exact same thing,....

Search up Free Be Tony's threads,+ you should be able to find it...

 

[FreeBeeTony]

Re: Mercruiser 165 Closed Cooling Conversion

Thanks for the mention Bondo...........

But mine was on a freshly rebuilt/"boiled-out" engine...........

 

[JJJ]

Re: Mercruiser 165 Closed Cooling Conversion

I did it to my 10 yr. old 4.3 and haven't looked back

Let me add this though, I lost a cylinder head due to rust (plugged a cooling port), so while replacing the heads, I blew all the rust and scale out of the block.
Put a closed system on with different heads, new manifolds and strainers in the system to catch/check on rust debris.
Pulled the strainers apart last year and there was very very little rust.

In my case I had to do it, only because I don't use the boat. It gets used about 2 weeks a year to go to the keys. The sitting the rest of the year was destroying the engine from the inside out.

There was ALOT of rust in the block, so unless you can remove most of it OR strain it out - it would be iffy as to whether to do it or not.

OF course the other option is to watch the engine rust itself away!

 

[Bondo]

Re: Mercruiser 165 Closed Cooling Conversion

Thanks for the mention Bondo...........

But mine was on a freshly rebuilt/"boiled-out" engine...........

Ayuh,....
Your thread is probably the Best "How To" there is on the net for freshwater cooling an Inline motor,...
Especially a "Creatively Engineered" system.....

 

[FreeBeeTony]

Re: Mercruiser 165 Closed Cooling Conversion

WOW...........now that is one of the best compliments I have ever gotten.

Thanks Bondo!!!

Have to admit........it was fun.........but I kinda like the SBC better.

 

[WOEISMEIGOTTA470]

Re: Mercruiser 165 Closed Cooling Conversion

WOW...........now that is one of the best compliments I have ever gotten.

Thanks Bondo!!!

Have to admit........it was fun.........but I kinda like the SBC better.

zombie-ing this thread...I just PM'd you FreebeeTony, I read that whole thread of yours back from 2005. I assume that you no longer have that boat/or setup. Either case, It has helped me decide on what I may end up doing with my new freshly rebuilt 165. I may just opt for a 1/2 FWC setup and leave the exhaust manifold RWC...we'll see. I find these old 6cyl motors cool/different.