compression problems..worth repairing?

[Judgey]

I have a 1978 70HP Evinrude. Model 70873C. I've been having alot of problems with stalling under load. Sometimes the boat can get up to plane , other times not, the more the load the less likely.

I completely rebuilt the carbs and checked the spark, no problems. As an afterthought did a compression check. Top 2 cylinders are around 90psi, the bottom gives no reading. I took out the tester and can feel air coming out when the engine is turned over but obviously when there is resistance the air goes elsewhere. I assume this means either a head gasket or cylinder/piston/ring problem. Either way seems that with the low compression on the other cylinders that a rebuilt is required and if so it may be time to put this old girl to pasture. Any thoughts?

 

[tashasdaddy]

Re: compression problems..worth repairing?

i would pull the cylinder head and investigate, could be a very bad blown head gasket. at the cost of new motors, it is be worth, taking a look.

 

[Sandhammaren05]

Re: compression problems..worth repairing?

Gasket leak will show up by water on the spark plug. Pull the head gasket and see, see what the cylinders look like. Those motors can run forever, can be honed, rebored to .020" and .030" oversize. No reason to abandon it. The later models through 1996 were essentially the same as the 1975 model, cubic inches were increased in 1988 and hp was measured at prop shaft, but essentially the same motor.

I have a 1978 70HP Evinrude. Model 70873C. I've been having alot of problems with stalling under load. Sometimes the boat can get up to plane , other times not, the more the load the less likely.

I completely rebuilt the carbs and checked the spark, no problems. As an afterthought did a compression check. Top 2 cylinders are around 90psi, the bottom gives no reading. I took out the tester and can feel air coming out when the engine is turned over but obviously when there is resistance the air goes elsewhere. I assume this means either a head gasket or cylinder/piston/ring problem. Either way seems that with the low compression on the other cylinders that a rebuilt is required and if so it may be time to put this old girl to pasture. Any thoughts?