96 Mercury 4cyl 2 stroke oil injection

[fishin0001]

Hi everyone need some advice, my motor got very hot and I noticed I have 125psi on 3 cylinders and 70psi on one, I did notice my motor has a dead head there's no cylinder head is it worth rebuilding or should I look into buying a good used motor and is the good place to by used motors
Thanks

 

[Chris1956]

You realize that an oil injection failure would affect all cylinders, right? You likely have another issue, like a clogged carb, wrong ign timing or failure in the cooling system.

 

[jimmbo]

Possibly cheaper to find a used Motor, but you could end up with someone else's problem. Rebuilding yours, you would also need to find out why it lost that Cylinder, or else the rebuild is likely to end up the same. Have you used a Borescope to look in the Cylinders, or pulled the Exhaust Cover off to look at the Piston Skirts? If the remaining 3 cylinders are fine, the Cost of rebuilding may be reasonable

 

[racerone]

Was water pump impeller replaced every 5 years?

 

[Chris1956]

Generally speaking, the undamaged pistons and cylinders will look brand-new, and the damaged ones will look all torn up.

 

[jimmbo]

IF one cylinder/piston got Hot enough to be nuked, the ones next it also likely suffered some Damage...
It may have been a Cooling problem, but since the OP hasn't revealed what 4 Cylinder design it was, there is some lack of Context. The 4 Cylinder Direct Charge Blocks had 2 Carbs, so a lean out should have bothered 2 Cylinders. The 4 Cylinder Loopers had 4 Carbs, 2 of which don't even supply fuel at low speeds

 

[Chris1956]

IF one cylinder/piston got Hot enough to be nuked, the ones next it also likely suffered some Damage...
It may have been a Cooling problem, but since the OP hasn't revealed what 4 Cylinder design it was, there is some lack of Context. The 4 Cylinder Direct Charge Blocks had 2 Carbs, so a lean out should have bothered 2 Cylinders. The 4 Cylinder Loopers had 4 Carbs, 2 of which don't even supply fuel at low speeds

My IL6 had overheat damage to #1 and #3, as it typical for that motor design. The rest of the pistons and cylinders were like new.

Those IL6 motors tended to run hotter on the top cylinders, as it took more water pressure to cool them.

I expect that #2 and #4 cylinders were spared due to the cold fuel on the bottom cylinder of the carb pair, negating the effects of overheat.

 

[fishin0001]

Was water pump impeller replaced every 5 years?

Ever year

 

[fishin0001]

Possibly cheaper to find a used Motor, but you could end up with someone else's problem. Rebuilding yours, you would also need to find out why it lost that Cylinder, or else the rebuild is likely to end up the same. Have you used a Borescope to look in the Cylinders, or pulled the Exhaust Cover off to look at the Piston Skirts? If the remaining 3 cylinders are fine, the Cost of rebuilding may be reasonable

I will definitely have friend do that