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90hp Oil Line replacement

D

Donald Boyer

Member
Hi all,

Mercury 90hp
1988
s/n 0b312461

Just doing a check of my 90hp, and noticed the clear hoses that run from the tank to the Oil pump are hard and showing cracks. I'm going to replace the whole lot, but just have a few questions:

What size is the hose?
Do I need special fuel hose for this application? (I'd like to replace with clear so the I can visually see that the line is full of oil)

When starting the engine for the first time after this job, how do I prime the Oil tubes so that the carbs recieve oil straight away and instead of nothing while the oil pump primes the tubes?

Thanks,

Donald.
 
Sorry, don't know the diameter but Merc sells it in "bulk" 10 or 15" lengths for 10 or 15 bucks - I don't know if it's "special" or not, but for under 20 bucks, given it's importance to the life of the motor, I wouldn't mess around with air hose for a fish tank (or the like).

There is a "bleed screw" on the oil pump. With the engine "off" you open the screw and gravity should fill the pump. The manual then suggests you run the motor at idle to bleed any air from the line between the oil pump and the fuel pump.

I would be inclined to fill the line with oil, using a syringe or the like, just to help it out a bit, and then bleed the pump before firing it up.
 
OK, I replaced all the lines. They were ALARMINGLY brittle!
Primed the pump and ran it on some 50:1 for 5-10mins just to be sure.

The Oil Pump was definitely working prior to replacing the lines, and since I've followed the Priming procedure correctly, I should be good to go. Or Should I run a tank of premix also?
 
The factory manual has a test for the oil pump output.------You run fast idle on 50:1 and collect oil from the pump.--Something like 18 cc of oil over 10 minutes.
 
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