CMB 67 help

[m brater]

I got my first inboard engine cmb 67 and have a newbe question. I put some marvel m oil in the glow plug hole w/ both glow plugs out and when I turn over the engine right before TDC it gets stiff like it should but then it has a clunk or ruff spot then you turn a little more past TDC and another clunk, kinda feels like a bent rod, bought it new though. My 7.5 outbrd pro has lots of compression but dosen't have any clunks, is that normal w/ the cmb 67? thanks for the help, Mike

 

[Propjockey]

I don't have a CMB, but I have had several engines do that when new. I think what you're feeling is the crank slipping past the tiny bit of play in the wrist pin while the piston is "jammed" in the top of the sleeve. It usually goes away after break-in.

 

[jklimpel]

....it's all good.

Run the engine in,..it will feel much smoother after 20oz of fuel.