35 hp johnson one cylinder no compression

[WFC]

Boat runs good at idle but boggs down at higher rpm. So I did a compression check. I took out both the plugs. Top cylinder showed 118 lbs. Bottom cylinder showed 0 lbs. When I put the top plug back in a test of bottom cylinder then showed 118 lbs.
any ideas?

 

[Texasmark]

Yeah. Take the top plug back out and retest the bottom cylinder....if it reads good you didn't have a good seat on your gauge or it malfunctioned... pressure release button stuck.

 

[WFC]

Yeah. Take the top plug back out and retest the bottom cylinder....if it reads good you didn't have a good seat on your gauge or it malfunctioned... pressure release button stuck.

OK here's what i did. I removed both plugs tested top cylinder it showed 118psi. bottom cylinder test showed 0 psi. Without removing gage from bottom cylinder I put plug back in top cylinder, bottom cylinder then pressurized to 118 psi. I then removed plug from top cylinder and bottom cylinder dropped to 0 psi

 

[Crosbyman]

check the gasket for a split

 

[F_R]

OK here's what i did. I removed both plugs tested top cylinder it showed 118psi. bottom cylinder test showed 0 psi. Without removing gage from bottom cylinder I put plug back in top cylinder, bottom cylinder then pressurized to 118 psi. I then removed plug from top cylinder and bottom cylinder dropped to 0 psi

Very interesting. Be sure to let us know what you find out.

What year is this 35hp?

 

[Dave1027]

Yep. Sounds like the head gasket is blown between the two cylinders basically linking them together.

 

[flyingscott]

Except for the fact both Fire rings would have to be blown, and one cylinder has compression so Not so sure its a split head gasket.