'54 Evinrude 15 hp compression

[trebot]

Tried compression test on my barn find. 0 on both cylinders. Is there a compression relief on this motor? If not, guess next step is check head gasket. Any thoughts?

 

[GA_Boater]

A compression release reduces compression, but not to zero. A motor needs compression to start.

Head gasket and looking for holes in the pistons is a starting point. Can you try the compression test on another motor in case it's the gauge?

 

[flyingscott]

First put penetrating oil/brake fluid/powersteering fluid or tranny fluid in the cylinders and let it sit overnite. Re-check compression then if still 0 take off the head I would also have a second gauge to double check.

 

[HighTrim]

Are the pistons moving in the cylinders?

 

[Bluestream]

Do not put brake fluid in the cylinders, it can eat your seals away

 

[trebot]

Pulled cylinder head and pistons weren't moving. Someone had failed to install the woodruff key on the crankshaft/flywheel and the flywheel turned but the crank doesn't. Find a woodruff and try again.

 

[jbuote]

I'm probably about to state the obvious, and I apologize if this is already known to you, but reading your last post..
​It's crazy the key wasn't installed.. lol

​The woodruff key is not what makes the flywheel turn the crankshaft.. It's having the flywheel nut torqued properly, and having good mating surfaces on the tapers..
​The key really just aligns the flywheel on the crankshaft for ignition timing purposes.. It's the torque and taper mating surfaces that hold the flywheel in place on the crankshaft..

​Clean mating surfaces and a torque wrench are a MUST if you don't want to shear a key in the future.. (Once it's installed that is.. haha.. )

​Again, I apologize if you already knew that.. (Betting you did already know that),
​But just wanted to be sure.. lol

For what it's worth...

 

[mla2ofus]

Crankshaft and flywheel tapers must be clean and dry with out any type of lube on them and as already said torqued to the right value.
Mike

 

[oldboat1]

So you may have no compression issues, right? That's good news. Need to try to find an OEM flywheel key for proper fit.

 

[F_R]

Flywheel key part number 120395

 

[HighTrim]

That's good news. What I figured, pretty rare you get both cylinders with 0 compression!

Someone was likely just working on it, dropped the flywheel on and it has sat like that for years. Might end up being a good find.

 

[trebot]

Shot some fuel in the carb and she fired on both cyl. Rebuilding carb, water pump and lower gear case. Think I found a sweet motor.

 

[Bluestream]

What is the compression now?

 

[trebot]

90-95 with old head gasket. Replacing head gasket, looks pretty rough

 

[oldboat1]

Have a new head gasket in hand before pulling off the head cover (trouble finding one for a 10hp I have). But when you get one, refinish the cover to take out any minor warping -- piece of maybe 400 grit wet/dry paper on a flat surface, maybe a piece of glass. Move the mating surface in a figure eight pattern until all surfaces are equally shiny.