Piston problem

[zach103]

Ok so toward the end of the season my engine was acting weird.. it would jerk the boat.. somone said it was because something was turning on and off.. so i started to take a look and found one wire that the mice bit part of the insulation off so i thouhgt that might be it.. but i was talking a look more and this is what i found when i looked inside the two port side cylinders.. the starboard side cylinders are fine

This is looking thru the hole for the spark plug looking at the top of the piston.. theres one big indent and like 4 or 5 small little ones

 

[RadarRick]

Re: Piston problem

Looks like something has let loose in there.

How is the other port side cylinder?

 

[zach103]

Re: Piston problem

its a v4 both port side cylinders look like that.. the two starboard side cylinders look normal

 

[metriccrescentwrench]

Re: Piston problem

If you're pretty sure something's amiss you may as well pull the head to get a better look. Post some more photos when you do.

 

[blimp]

Re: Piston problem

looks a lot like factory stamp on an OS piston...

 

[zach103]

Re: Piston problem

looks a lot like factory stamp on an OS piston...

but why would they stamp it there?? seems kind of odd..


i am in the process of taking it off.. jus gunna run to the hardware store to get the knuckle for the socket

 

[wilde1j]

Re: Piston problem

Ok so toward the end of the season my engine was acting weird.. it would jerk the boat.. somone said it was because something was turning on and off.. so i started to take a look and found one wire that the mice bit part of the insulation off so i thouhgt that might be it.. but i was talking a look more and this is what i found when i looked inside the two port side cylinders.. the starboard side cylinders are fine

This is looking thru the hole for the spark plug looking at the top of the piston.. theres one big indent and like 4 or 5 small little ones

When a motor "would jerk the boat", it's usually caused by a worn clutch dog/forward gear in the gearcase and typically nothing to do with the powerhead. This is typically caused by "gentle shifting".

 

[zach103]

Re: Piston problem

When a motor "would jerk the boat", it's usually caused by a worn clutch dog/forward gear in the gearcase and typically nothing to do with the powerhead. This is typically caused by "gentle shifting".

Ok how do i fix that loll

heres two new pics with the head off

 

[wilde1j]

Re: Piston problem

Start with an OEM shop manual, then ask questions for what you don't understand.

 

[F_R]

Re: Piston problem

The big hole is a center drill. A point goes in it to hold it in a lathe when they finish the outside. Here is a brand new piston. See the center drill? This one is oversize, thus the .020" stamping.

I believe somebody deliberatly made the other holes with a punch. It is common for mechanics to do that for identification purposes when they tear an engine apart. Has yours been apart?

 

[zach103]

Re: Piston problem

I have the manual and looked at all the piston heads didnt see the holes so thats why i asked..

that deff looks like it.. the powerhead has not been touched by a mechanic since ive owned it.. only the lower unit. thats why im going thru my manual and replacing the things that should be replaced and cleaned

 

[surrender]

Re: Piston problem

I have the manual and looked at all the piston heads didnt see the holes so thats why i asked..

that deff looks like it.. the powerhead has not been touched by a mechanic since ive owned it.. only the lower unit. thats why im going thru my manual and replacing the things that should be replaced and cleaned

On my cross flow v-4 all four piston tops have the center hole and a few(2,3 or 4) smaller "holes". All look good and everything has been running pretty good all year. What your looking at may be normal.