Oil Injection System Q's : 175 HP Mercury V-6

[P51D]

I have a ?91 or 92 175 HP Mercury V-6, 2.5 liter, Serial # OD223009. Just got it in the water last week, and discovered a cracked cap for the oil reservoir on the engine (it made QUITE a mess). I ordered a new cap and gasket, but they won't arrive 'til next week.

I'd like to get the boat out for at least one quick run this weekend. I was planning on running it on a portable tank with pre-mix. I was going to:

1. Hook up to the pre-mix portable tank

2. temporarily immobilize the reservoir float in the "Full" position to avoid the low oil alert.

3. Loosen the remote reservoir cap to prevent pumping more oil into the engine reservoir, preventing another oil mess. This is essentially creating a big air leak in the remote tank to keep it from pressurizing.

Then I got to thinking (uh-oh):

a. Will it hurt anything in the engine if it isn't working against a pressure in the remote oil tank?

b. If the reservoir on the engine does run dry, will it hurt the oil pump, or some other component "upstream" of the pre-mix that might depend on oil from the reservoir?

c. Does the reservoir & pump on the engine depend on pressure via the remote tank to feed the oil pump, or is gravity feed enough once you have oil in the engine mounted tank (I know you need pressure to feed the engine mounted reservoir)? Put another way, if you have oil, but no pressure, in the engine mounted tank, will it feed and mix oil properly?

THANKS

P51D

 

[P51D]

Re: Oil Injection System Q's : 175 HP Mercury V-6

Also, will "double dosing" the engine with oil harm anything? It'll be running on the pre-mix, plus whatever the VRO delivers from the tank on the engine.

 

[gss036]

Re: Oil Injection System Q's : 175 HP Mercury V-6

I think you answered your own question. The oil pump is gravity fed. Don't know how long you are going to be running, but, you could just let the tank on the engine fill up and the loosen the cap on the reservoir for the boat tank and when you need more oil in the engine tank tighten it back for a few mi utes until it fills up. The engine tank will last for quite a while.

 

[P51D]

Re: Oil Injection System Q's : 175 HP Mercury V-6

Thanks, GSS! I'll try it that way.

 

[wilde1j]

Re: Oil Injection System Q's : 175 HP Mercury V-6

The only thing you may damage is the oil pump itself (expensive). It's a gear pump as I recall and lubed by the oil it pumps. If I were going to run w/o it, I'd take the pump off, remove the driven shaft which is keyed to the pump and replace the pump. That way the pump would not rotate. The only risk then would be if the bushing at the internal end of the driven shaft came loose.
Jim

 

[P51D]

Re: Oil Injection System Q's : 175 HP Mercury V-6

Thanks, Jim. I ran it (on pre-mix), AND made sure there was always oil in the engine mounted tank. Gravity seemed to be feeding the pump fine, since the oil level did go down some. My concern was that the system might rely on both gravity and pressure to feed the oil pump properly.

At any rate, I got done what I needed to get done, and thanks to all for the input.

P51D