Oil Injection - The Hull Truth

fly2xsaol · 07-08-2009, 08:46 PM

Thanks for your help in advance.

I have a 93 Merc 150 Blackmax that I am having the powerhead rebuilt. Since the engine is older and I have herd horror stories about the oil injection system on outboards this old, is it wise to disconnect the oil injection system and mix the oil yourself?

Pros? Cons? Any system mods that will have to be done? Will the cards have to be rebuilt more often?

Thanks,

New Member

A1 Outboard · 07-09-2009, 04:38 AM

Oil injection that works properly is great. The Mercury system uses a plastic gear on the crank to drive the pump. This gear has been known to fail. The system uses plastic hoses which harden and break when with age. If you decide to keep the oil injection the gear and hoses need to be replaced at rebuild. There are aftermarket electric pumps, that replace the mechanical pump, that work well. Mixing your own oil can be a problem with a built in tank. The tendancy is to mix more oil than is needed, or to forget the oil all together. Too much oil causes spark plug fouling and smoking. Too little oil can cause failure. You may never have a problem, but, when someone else uses the boat they may not add oil correctly. The oil in fuel does not cause carb problems, it is the poor quality fuel with alcohol. The alcohol can also cause the oil in the fuel tank to separate from the gas. If you keep the oil injection, you need to watch the hoses for leakage and watch the oil tank to be certain the oil level is dropping. If you remove the system, you need to be certain that everyone who fuels the boat knows that oil MUST be added to the fuel in a 50-1 ratio.