1973 115 V4 crossflow
On the water yesterday running like a champ @ 5000 rpm....then rapid fire knocking and the motor died. Probably had about 35 minutes of running time (on and off) including a 5 mile ski prior to failure. Tried to restart and motor was seized. Pulled plugs and # 3 electrode had been struck by piston. After the motor cooled it would restart with substantial knocking.I shut it back down immediately.
Tore into it this morning and found the #3 rod to crank bearing disintegrated and evidence of major heat discoloration.
I know what happened but not why.
When I pulled the plugs all four were dry. Not oily like they should be.
Cylinder walls are not damaged with the exception being #3 slight scuff...aparently from the bearing failure.
Exhaust housing dry soot, not oily. Same thing behind exhaust cover.
The pistons and exhaust route all look steam cleaned. I believe water was ingested causing lube failure causing bearing failure.
Head gaskets showed no sign of failure.
First start of the day was normal, about 4 seconds of cranking while choked it fired right up and after about 20 seconds of fast idle (2000 rpm) it idled perfect at 600 rpm.
Water was flowing out the tell tale like normal and water pressure was normal.
Motor has about 160 hours since rebuild in 2004.
Two days ago I replaced the lower unit oil and had the lower unit off for a clean up.
Man this thing ran sweet. I'm sick thinking I fowled up.
Is it possible for water to get forced back thru the motor via the exhaust housing due to a bad Exhaust housing to gearcase seal?
A few pictures of todays teardown...Photos
On the water yesterday running like a champ @ 5000 rpm....then rapid fire knocking and the motor died. Probably had about 35 minutes of running time (on and off) including a 5 mile ski prior to failure. Tried to restart and motor was seized. Pulled plugs and # 3 electrode had been struck by piston. After the motor cooled it would restart with substantial knocking.I shut it back down immediately.
Tore into it this morning and found the #3 rod to crank bearing disintegrated and evidence of major heat discoloration.
I know what happened but not why.
When I pulled the plugs all four were dry. Not oily like they should be.
Cylinder walls are not damaged with the exception being #3 slight scuff...aparently from the bearing failure.
Exhaust housing dry soot, not oily. Same thing behind exhaust cover.
The pistons and exhaust route all look steam cleaned. I believe water was ingested causing lube failure causing bearing failure.
Head gaskets showed no sign of failure.
First start of the day was normal, about 4 seconds of cranking while choked it fired right up and after about 20 seconds of fast idle (2000 rpm) it idled perfect at 600 rpm.
Water was flowing out the tell tale like normal and water pressure was normal.
Motor has about 160 hours since rebuild in 2004.
Two days ago I replaced the lower unit oil and had the lower unit off for a clean up.
Man this thing ran sweet. I'm sick thinking I fowled up.
Is it possible for water to get forced back thru the motor via the exhaust housing due to a bad Exhaust housing to gearcase seal?
A few pictures of todays teardown...Photos
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