advancing the timing on the IL 4 motor to gain performance

[Bt Doctur]

 

[Bondo]

Ayuh,.... Detonation at it's finest,...

Did it hurt the piston,..?? deck,..?? head,..??

 

[Bt Doctur]

piston still has its head intact, no holes ,but #1 and #3 took a beating judging by the head gasket

 

[Scott Danforth]

My guess is also an overheat based on the exhaust gasket

check the head for flatness

 

[Bt Doctur]

to put this in perspective on buying your first boat at a great price more pics to follow
26-27 foot boat show special when offered Like a Sundancer model , aft cabin ,raised help station, etc
powered by twin IL 4 140 Hp motors 2 barrel carbs, Alpha drives
Owner: "Lets see how fast we can go with the timing advanced to 6 degrees"
" 40O0 rpm, sounds great, then BANG,EXAUST POPPING SOUNDS, ETC
One more thing,PO advanced tinging and unplugged the TKS to make it run better prior to sale.
No presale inspection was done.

 

[Bt Doctur]

 

[harringtondav]

GM knows engines, and their Marine engines are robust. Until someone starts tinkering with them, or fails to maintain them.