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Author Topic:   engine help
SWarren posted 02-27-2001 07:35 AM ET (US)   Profile for SWarren   Send Email to SWarren  
I have 95 twin 115 motors on my revenge. This past weekend I cranked them up for the first time in about 3 weeks. After I ran them on the hose for a while I noticed some oil/exaust coming out of the prop area. It was doing this on both motors. Am I correct to assume that this is the oil that builds up in the carbs during storage. I know it is not the oil from the lower unit, because it looked like exahust oil and I change the lower unit oil all the time, and it never looks like this. Is this just a function of the vro tanks draining oil into the motor while the boat in stored? My yamahas never did this, they just burned rich for a little while after it had been sitting. Thanks.

Steve

Clark Roberts posted 02-27-2001 08:05 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Steve, I have seen this (black oil dripping from lower unit,,, exhaust/propshaft) on other OMC engines (I'm assuming OMC since you mention VRO!). You will get differing answers even from mechanics, but my guess is that the VRO is metering too much oil. This could be a clue that the VRO is about to quit working alltogether but since both are doing same thing, who knows... you could disconnect the VRO on one of the engines and premix (in an independant tank) at 50:1 or maybe even 60:1 and see if that engine stops the dripping! Then you will know it's the VRO supplying too much oil... I don't think there's an adjustment for more/less oil on the VRO system. Others may have better suggestions.... Happy Whalin'.. Clark.. Spruce Creek Navy
SWarren posted 02-27-2001 08:19 AM ET (US)     Profile for SWarren  Send Email to SWarren     
Clark,
Sorry they are OMC motors ( Johnsons). I have two vro tanks, one for each motor. I thought that maybe they just always ooze oil if it is not running. This is why the carbs get oil in them when they sit for a few weeks. I hope they vro is not about to stop working. Any idea on cost to put new tanks in? Thanks.

Steve

SWarren posted 02-27-2001 08:24 AM ET (US)     Profile for SWarren  Send Email to SWarren     
Clark,
Forgot to mention that I check the tanks after every time I go out to see if they are working. They level is always the same on both tanks, so there is no indication that way of tanks going bad.
Clark Roberts posted 02-28-2001 06:00 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Steve, I'm no expert on anything but usually have an opinion on everything! The VRO was just a guess at what the problem may be. If it is the VRO (OMC's Variable Ratio Oiling) it's most likey the pumps and not the tanks. The tanks are unpressurized and simply are a reservoir. The pump is mounted under engine cowling and is combined with the fuel pump (one unit). The oil is pumped via diaphram action created by the "plus-minus" pressure pulses of the crankcase therefore more oil for more rpm and vice-versa. As the oil is pumped it is mixed into the gas as it exits the fuel pump and then on to the carbs. Now it's possible (my opinion again) that, since oil changes viscosity with temp changes, the oil mixture ratio is higher as ambient temp rises (oil is thinner and pumps more easily) and lower in cold weather (oil is thicker and pumps less easily). If this is true, then your oil leaking problem may go away in cold weather!??? Just grabbing at straws here, mind you! VRO pumps fail due to cardiac arrest as the diaphrams loose ability to flex and/or rupture. Disconnection is fairly easy and the pump can be left in engine with only the fuel pump side working. There are even plugs supplied with engine (clamped onto fuel/oil line,, usually yellow plastic gadgets) to seal off the incoming oil line from tank. It's better to remove entire pump and replace with standard fuel pump (IMHO)... I have several VRO pumps hanging on my garage wall..... Checking oil level in tanks is a good way to verify that oil is being used and you say that is the case but can you determine if ratio is too high? Seems that it would take a long cruise to do it accurately.. What about trying the premix in separate tank as suggested... this would "nail it down" don't you think? Best to check with OMC expert in any case... hope some of the above ramblings help out! Clark... Spruce Creek Navy
skookum point posted 02-28-2001 11:25 PM ET (US)     Profile for skookum point  Send Email to skookum point     
Just curious - what happens when a VRO pump fails? I assume no oil means no lubrication which means a major powerhead rebuild. Am I right? Does it make any sense to disconnect the VRO system and use mixed fuel instead? Was the VRO system intended to improve engine lubrication, to make it run cleaner, or just to make refueling easier? You may have guessed I have an OMC with VRO and I worry about offshore engine failure.
John
SWarren posted 03-01-2001 09:01 AM ET (US)     Profile for SWarren  Send Email to SWarren     
Thats a great question. Most people that I have talked to that have been around omc for a long time say to bypass the vro. Others say that in the early 90's they fixed it. I am leaving mine hooked up. They made those tanks for a reason, so why not use them. I would be curious as to what the OMC vets on the forum think.

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