power loss - help

[whalerjet]

My 1994 OMC 115 will lose power after 20 minutes. Peak RPM drop from 5000 to around 4000. This is consistant at around 20 minutes. Compression is 120 in all four cylinders, coils test with spec. while cold, flywheel indexed and it fires right on for each cylinder. This is a VRO engine and it is not disconnected. No warning buzzer. My first thought is the power pack is breaking down since the problem develops at the same time. I did replace the #1 plug wire, but that didn't solve the problem. I am wondering if it may be the VRO or the anti siphon valve at the fuel tank. Any advice would be appreciated.

 

[whalerjet]

Re: power loss - help

What I mean by no warning buzzer is that it has not/did not sound off. The engine did not overheat. Just wanted to clear that up.

 

[ob]

Re: power loss - help

Does motor smoke more than did when new on cold start-up?vro's are notorious for internal seal leaking into fuel half of pump assy.resulting in oil rich mixture.If you suspect vro I would not hesitate to defeat it and mix 50:1.

 

[whalerjet]

Re: power loss - help

Thanks OB,<br /><br />It is not really a smoker, but the plugs appear a little wet. Almost as if they are too cold, but they are the factory plugs. I have heard more bad about the VRO than good. Can the leakage you mentioned affect the performance I mentioned? What is the procedure to disconnect the VRO as I will do that anyway?

 

[ob]

Re: power loss - help

you could perform a consumption check on vro tank per gallon of fuel to determine oil rich condition but I would disconnect.procedure for defeating the vro is fairly simple.remove oil line from oil pump half of unit and cap off nipple.next either plug or remove oil line from oil tank to motor assy. some people leave line routed and plugged as future owner may want to re-able oil system.dis-connect the two wire lead from vro tank to motor.this is the low oil level alarm wiring.next I believe your year model has a four wire harness that goes from vro pump to a rubber plug adapter .this adapter is approx. 2" long and about 3/4 " diameter. unplug and cap the disconnected ends.this is your no oil pressure and fuel pump alarm leads.the only alarm you will have remaining is your motor high temp alarm.You can test to insure it is still working by turning on key and grounding the tan colored wire to engine block .location of this wire can be found by tracing the temperature sensor on power head end of engine bock .Next mix 50:1 oil in fuel tank after discarding any leftover fuel as it is difficult to determine the amount in tank to accurately mix.after mixing new batch in tank disconnect fuel line from motor and depress ball valve while purging fuel line into clear container until you have established that the fuel oil mix has reached engine and purged all raw gas from fuel line.By the way , the fuel half of the vro pump works just fine as a fuel pump only set-up.In the future if you experience a fuel pump failure you can buy a conventional fuel pump as replacement significantly cheaper than the vro pump . Also, wondering if your power loss drop in rpm's is an immediate drop as possibly the S.L.O.W. system if equipped is detecting high engine temp and limiting rpms.I believe that if that is the case that this system by design is suppose to drop rpms to around 2500 though. Just a shot.Try looking into cooling system operation .Good flow from engine , thermostats.