cmb 67 gh cyl leaking water

[mike farrell]

I have cmb 67 green head and I was having a problem with water getting in my boat so I ran it on the stand with water pressure and noticed water coming out around the cooling fins on the cylinder I think its making my engine quit after a couple of laps any body ever hear of this leaking.

 

[steve wood]

I have cmb 67 green head and I was having a problem with water getting in my boat so I ran it on the stand with water pressure and noticed water coming out around the cooling fins on the cylinder I think its making my engine quit after a couple of laps any body ever hear of this leaking.

never use water pressure from a hose or pump,way too much pressure. they will all leak like this

if someone has removed head shims,check to see if the water jacket is bottoming on the case. if it is, the best way to fix it is to m achine some material off the bottom of the water jacket. in a hurry, put a thick head shim on top of head button,to raise the water jacket up a little. check the oring for damage also

 

[Dasboatman]

Hey Mike,

Based on what you are saying - K.I.S.S. Principle says - - replace the O-ring and try again. I have had issues with these o-rings in the past and have gone to a better quality aftermarket product. CHEERS !!! Bob

 

[misshydro]

Hey Mike,

Based on what you are saying - K.I.S.S. Principle says - - replace the O-ring and try again. I have had issues with these o-rings in the past and have gone to a better quality aftermarket product. CHEERS !!! Bob

and if that dont work,,put a thin coat of RTV as a gasket/make a water tight seal..

 

[FloridaScaleBoater]

Hey Mike,

Based on what you are saying - K.I.S.S. Principle says - - replace the O-ring and try again. I have had issues with these o-rings in the past and have gone to a better quality aftermarket product. CHEERS !!! Bob

and if that dont work,,put a thin coat of RTV as a gasket/make a water tight seal..

No thanks,,, NO Monkey S*#t for me,, if the O-Ring isn't sealing... Somethings wrong,,Find the problem

 

[Hydro Junkie]

I have to agree on NO RTV. RTV is known for breaking up over time and clogging small fluid lines. Unless an instruction sheet or manual specifically says to use the stuff, I WON'T!!!!!!!!!!!!!!!!!!!!!!

 

[Duck899]

I have to agree on NO RTV. RTV is known for breaking up over time and clogging small fluid lines. Unless an instruction sheet or manual specifically says to use the stuff, I WON'T!!!!!!!!!!!!!!!!!!!!!!

Like

 

[jwo]

Hey Rob, Take the water jacket and use a fine grit sand paper on a flat surface and gently remove material from the bottom. Also check to see if the engine has an aluminum head shim. If it does replace it with a good one. I have found that the original aluminum shim tend to squish over time. Had the same problem last year. John

 

[Mike Cathey]

You definitly want to install the head button and water jacket and hold the motor up to the light and you should see a small gap beteween the case and the bottom of the water jacket. If you don't see it, you need to remove some material from the bottom of the water jacket. Pretty common on the CMB's when you start getting lower head clearences. I did a motor for a guy that had .020 head clearence and the water jacket was still was hitting the case (this was brand new motor).

A little smear of petroleum jelly on the inside of the O-ring before you install it will ensure it doesn't roll on you.

 

[Terry Keeley]

Mine was leaking past the head bolts and coming out the bottom of the holes, think it's worse if you use "loose" stainless screws like I do.

I installed some 6-32 x 1/8" ss set screws at the bottom of the holes with a generous amount of red locktite.

Problem solved! B)

 

[bsmtboy2]

I learned from Stu Barr himself that when you use WD40 after running to clean out the water lines and coat the head screws it eats at the rubber O ring or swells it up distorting it.. Stu says use alcohol to clean it out to save the gasket from damage. I had this same thing happen 2 years ago and a new o ring later problem went away. Been using alky ever since with no issues.