Will a crack in cylinder wall to water jacket cause a melted piston on 150 black

[gr82fish]

I have a 150 blackmax that melted the top off #5 cylinder. Wondering which came first- the melted piston causing the crack or the water in cylinder causing piston damage. Engine was slow to pick up speed a every time I used the boat about a year or so before this happend. Was doing about 55 mph when it started making noise.

 

[Chris1956]

Re: Will a crack in cylinder wall to water jacket cause a melted piston on 150 b

Re: Will a crack in cylinder wall to water jacket cause a melted piston on 150 b

I would think the expansion of the piston during the overheat caused the crack.

 

[gr82fish]

Re: Will a crack in cylinder wall to water jacket cause a melted piston on 150 b

Re: Will a crack in cylinder wall to water jacket cause a melted piston on 150 b

Any idea why only one cylinder would overheat? The other 5 look great.

 

[WillyBWright]

Re: Will a crack in cylinder wall to water jacket cause a melted piston on 150 b

Re: Will a crack in cylinder wall to water jacket cause a melted piston on 150 b

Not from overheating. Detonation is caused by poor fuel, lean carburetion, improper timing (any 1, 2 or all 3). I typically set max timing 2 degrees below spec on older motors for that reason.