What is this salt on my outboard block and spark plug holes?

[Miamipatriarch]

I just found this salt in the marked areas of the outboard and spark plug holes as shown on the pic

Can anyone share what this means?

Yamaha outboard 2 stroke V6 225 hp

 

[racerone]

Looks like the motor overheated at some time !----Over time water does seep through the head gasket.----Very little over a long time.----What inspection was done due to the overheat event ?

 

[Miamipatriarch]

Hey. Thanks. I think I first noticed the overheat sign on the engine one time after getting somewhat stuck in a sandbar. Right after this incident, after trying to get out and return to the marina that engine turned off and I arrived at the dock with its twin. I flushed them on the spot when I pulled it off the water, later dropped the leg / lower unit on its twin and saw very little sand left around the pump, cleaned it and repositioned the lower unit. Because I saw this engine on the pic with a tell tale stream, water through the propeller, and its twin had very little sand left, I assumed it was cooling fine and I decided not to check its water pump. They are due for service in October. Any advice?

 

[Scott Danforth]

Any advice?

should have changed the impeller when you had it apart.

sand will kill the efficiency of the impeller. Overheats kill the motor.

do a compression check. If you overheated enough for the motor to quit. you most likely you collapsed the pistons or scored the cylinders.

 

[Miamipatriarch]

should have changed the impeller when you had it apart.

sand will kill the efficiency of the impeller. Overheats kill the motor.

do a compression check. If you overheated enough for the motor to quit. you most likely you collapsed the pistons or scored the cylinders.

Thanks. I took apart the twin engine. There was no sand in the impeller casing or anywhere close to the impeller, and I didn't change the impeller on that one because it looked immaculate. I am concerned I didn't do the same inspection for this engine on the pic though. They are just so heavy to handle...sigh

 

[Miamipatriarch]

should have changed the impeller when you had it apart.

sand will kill the efficiency of the impeller. Overheats kill the motor.

do a compression check. If you overheated enough for the motor to quit. you most likely you collapsed the pistons or scored the cylinders.

Warm engine compression test today vs Cold engine test 5 months ago
Piston # PSI PSI
1 119 115
2 121 120
3 121 120
4 101 110
5 114 115
6 110 115

Two different compression testing gauges used
Thanks