What Would Cause This

[HumberJewel]

1970 70 HP
Lost power while waterskiing. Limped home. Low compression on center cylinder.
Pieces missing from the center piston.



Center piston connecting rod sloppy on the crank.
Center piston rod cap is white and dry, the others are black and damp.

 

[HumberJewel]

I was going to undo the rod caps through the intake, but the rod bolts have weird heads.
What's the correct tool for these bolts?

 

[racerone]

There was no 70 HP motor in 1970 !!---Or is it a 1974 model ?-------A plugged / partially plugged carburetor can really mess that up.---Or oil recirculation was blocked somehow. ------Time to look for a bunch of repair parts I guess.

 

[racerone]

A 5/16" 12 point socket.-----Not really weird.-----Standard for super high strength rod bolts made with alloy steel.----About 180,000 PSI in yield I believe.-----The motor has to come right apart.----Can not be repaired the way you are trying !!

 

[faztbullet]

Looks like it ate a wristpin bearing..common problem on the old I beam style rod

 

[HumberJewel]

Thanks everyone, and ya, 1974.
I wasn't really considering repairing it.
I want to take out the piston to see the skirt (curious). 5/16 - 12 pt isn't in my toolbox (yet)

Why does the top of the piston look like this? Debris from the bearing carried through the intake port and bounced around?

 

[faztbullet]

Ya got it..

 

[HumberJewel]

I got got a 5/16" 12 pt socket today!

One tiny piece missing from a connecting rod bearing retainer and both retainers broken. All 16 rollers accounted for.