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Author Topic:   Yamaha 90-HP Internal Oil Tank
Sixer posted 11-10-2002 08:04 PM ET (US)   Profile for Sixer  
1988 Yamaha 90-HP has a built in oil reservoir under the hood with small capacity. Has anyone tried to connect a remote oil reservoir? Is this possible? Thanks for any insight.
John Bocskay posted 11-10-2002 08:18 PM ET (US)     Profile for John Bocskay  Send Email to John Bocskay     
I had twin 70s, they don't burn that much oil, you can run them for a long time before adding oil, don't know if it's worth it.
jimh posted 11-11-2002 08:01 AM ET (US)     Profile for jimh  Send Email to jimh     
In the Yamaha engine, it looks to me like the oil tank is located above the oil injection pump. This means the oil is supplied to the pump inlet via a gravity feed. I don't think the oil injection pump is necessarily self-priming.

One of the recommendations in the manual is to manually bleed and prime the oil injection pump whenever the engine has not run for a while.

In oil systems where the oil tank is located remote from the engine, there must be some pumping action to draw the oil into the engine. I don't know if you'd get that with the Yamaha.

The capacity of the oil tank in the 90-HP is about three quarts. Since the mix ratio is variable, how long this will last depends on the speed you run the engine.
Even at 50:1 oiling, the tank should contain enough oil to mix with about 37 gallons of gasoline. With a 90-HP outboard, 37 gallons of gasoline can take one quite a distance.

Of course, you don't get the benefit of all the oil in the tank, as the "low oil" alarm will come on long before the last drop of oil is consumed.

Most owners think the internal oil tank is a definite benefit. It eliminates the remote tank and the hose connection to it. This removes some of the clutter from the transom and splash well area.

John from Madison CT posted 11-11-2002 08:13 AM ET (US)     Profile for John from Madison CT  Send Email to John from Madison CT     
I wouldn't mess with trying to add an external reservoir to the Yamaha 90's internal tank. You'll average less than 50:1 in oil use, and the 3/4 gal tank goes a long way.

JimH is correct, the pump needs to be bleed to work properly.

John from Madison, CT

Sixer posted 11-11-2002 11:31 AM ET (US)     Profile for Sixer    
Thanks guys, thought it would be more convenient/safe if needed to refill on the water.
jimh posted 11-11-2002 01:30 PM ET (US)     Profile for jimh  Send Email to jimh     
To refill the internal oil tank on the 70/90-HP Yamaha, it is best to use a funnel, especially if you are pouring from a 1-gallon capacity oil container. Those large oil containers are hard to handle without spilling.
Bigshot posted 11-11-2002 02:02 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
That tank will run about 2 27 Pates before a fillup. You will run out of gas before you need to fill the oil. Just make sure you top off the oil when you top off the tank and you'll be fine. If you decide you want a remote tank, I have a like new Yamaha tank 3 gal? with pump.
The Chesapeake Explorer posted 11-12-2002 11:01 PM ET (US)     Profile for The Chesapeake Explorer  Send Email to The Chesapeake Explorer     
Has any one had any problems with the Yamaha oil Injection on the 90. I had VRO on my 88 90 Evinrude and took it off about 1992 after 2 engine siezes..Too many troubles, oil horn blowing.. sensors in the oil tank messed up. Long story Ill tell some day and some ,money out my pocket till I started mixing 50-1 and quit fooling with it. 1500+ hours now on it.
John from Madison CT posted 11-13-2002 07:54 AM ET (US)     Profile for John from Madison CT  Send Email to John from Madison CT     
You almost never hear of a oil injection failure on Yamaha OB's.

As JimH stated, they are gravity fed and the mikuni pump is very reliable. I trust them 100%.


Bigshot posted 11-13-2002 09:25 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
The pump is actually conected to the crankshaft on these yamahas and moreso gravity fed. Gear on crank is metal, not plastic like on mercs. This system will outlast the rest of the engine.

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