Mercruiser 165HP 6 Cylinder Inline

[jarruiz13]

So I recently got a boat nearly for free with a Mercruiser 165 HP 6cylinder Inline engine, according to previous owner he was using this boat as a project but eventually got bored and quit working on it. He said the motor did work but never stated in what year. He did give me a new head for the motor. I came around moving the motor as it was missing its front motor mount. In that process i checked the dipstick and it was milky-coffee looking. So my million dollar question is what can it be, is it time for me to replace the heads and see what is going on. Or simply do a rebuilt on the engine? I bought the manual from this website so I am not sure what to incline as more problems arise gives me the depression that it will cause more of an hold up to get this project of mine completed. Any suggestion will be great! Thank you

 

[Fishermark]

... i checked the dipstick and it was milky-coffee looking. So my million dollar question is what can it be...

Only one thing it can be - water in the oil.

There are several ways the water can get in the oil. You will have to check them out as you go. Could be a bad manifold or riser... could be a cracked engine block... maybe a few more things. You will not know till you check. The good news? It doesn't cost anything to disassemble and check. If nothing else, you will get some good experience disassembling an engine! That is a good basic long lasting engine. Worth your while to do some more investigating.

 

[WOEISMEIGOTTA470]

X2 on what Fishermark said. At least you got a new cylinder head in the deal! That helps. Hopefully in your case, if there is a crack or leak, it's limited to the cylinder head. Before you pull anything apart, you could perform a leak-down test, that will tell you the condition of each cylinder, and may help pinpoint where a leak would be coming from. Or if you don't have access to a leak-down tester, just pressurize each cylinder via the spark plug hole with air using a compression tester hose with the schrader valve removed. Remove the valve cover to verify both valves are closed (TDC comp stroke). Listen for where air is escaping from, (manifold, cooling system, crankcase).

Good thing is these engines are designed simply, and are fairly inexpensive to rebuild. I can't wait to try mine out!
Good luck!!

 

[Fishermark]

A leak down test is a good idea. In addition to the test mentioned by WOE (the full name is too long! ;-) ) - you also need to pressurize the cooling system. That may be a little more difficult depending upon what you still have attached to the engine.

 

[jarruiz13]

Sounds good with all the feedback I am going to try this weekend and see where this leads me to. Is their a way to make my own freshwater cooled system or would I need to buy the actual kit? Any ideas to avoid these problems in the long run.

 

[Bondo]

Sounds good with all the feedback I am going to try this weekend and see where this leads me to. Is their a way to make my own freshwater cooled system or would I need to buy the actual kit? Any ideas to avoid these problems in the long run.

Ayuh,..... FreebeTony built his own system, 'n documented in right here at iboats, 'bout 10 years ago, I believe,....

Tony still stops by occasionally, 'n his thread is no doubt in the archives,....

 

[WOEISMEIGOTTA470]

A leak down test is a good idea. In addition to the test mentioned by WOE (the full name is too long! ;-) ) - you also need to pressurize the cooling system. That may be a little more difficult depending upon what you still have attached to the engine.

Yeaahhh i know it's too long lol...WOE is good, or Jim ;-)

On the subject of FWC...I was going to build my own kit as well using a 4" heat exchanger from a 470 engine. But then I got lucky and found an entire kit for sale designed for the GM inline 4's and 6's. These kits can be hard to find but if you look long enough you might get lucky like me. I actually still have my spare 470 heat exchanger, and a spare t-stat housing and reservoir brand new that I had bought. I was going to sell these items eventually...

 

[jarruiz13]

Yeaahhh i know it's too long lol...WOE is good, or Jim ;-)

On the subject of FWC...I was going to build my own kit as well using a 4" heat exchanger from a 470 engine. But then I got lucky and found an entire kit for sale designed for the GM inline 4's and 6's. These kits can be hard to find but if you look long enough you might get lucky like me. I actually still have my spare 470 heat exchanger, and a spare t-stat housing and reservoir brand new that I had bought. I was going to sell these items eventually...

Yeah, I have been looking and the rough price for the GM 6 inline kit is running about $1k. I was trying to see if I can make myself a heat exchanger and construct it out of copper & nickel. But I am trying to get all info, if I need a separate thermostat housing, thermostat and all those nice information.

 

[jarruiz13]

Yeaahhh i know it's too long lol...WOE is good, or Jim ;-)

On the subject of FWC...I was going to build my own kit as well using a 4" heat exchanger from a 470 engine. But then I got lucky and found an entire kit for sale designed for the GM inline 4's and 6's. These kits can be hard to find but if you look long enough you might get lucky like me. I actually still have my spare 470 heat exchanger, and a spare t-stat housing and reservoir brand new that I had bought. I was going to sell these items eventually...

Yeah, I have been looking and the rough price for the GM 6 inline kit is running about $1k. I was trying to see if I can make myself a heat exchanger and construct it out of copper & nickel. But I am trying to get all info, if I need a separate thermostat housing, thermostat and all those nice information.

 

[Scott Danforth]

Having worked for one of the heat exchanger companies that feeds the marine market, its just copper sheets, tubes, baffles, and castings. the problem building them is the core and getting the baffles correct. too much restriction and you choke off the circulation pump or raw water pump. to little restriction and the heat transfer isnt there. Then there is keeping the flow rate correct. too slow, and crap precipitates out plugging the heat exchanger. too fast and you wear out the core.

while a kit would cost $800-1000, the heat exchanger cost is about $600 of that. Which about half that cost is the copper alone based on LME pricing for that date. The rest is labor and packaging.

can you build one - sure. however is it worth building yourself. depends on your skills. the average 5" heat exchanger has 276 1/4" tubes (0.248"), each one secured to the baffles, then sealed to the headers.

you could get a heavy duty transmission cooler and simply change the connections and end caps. this would get you the core. you would have to add the appropriate dividers.