87 70 HP EVINRUDE VRO CUTTING DOWN AT FULL THROTTLE

HI<br /> MY 87 EVINRUDE VRO LOOSES SPEED SOMETIMES AT FULL THROTTLE . I WILL DRIVE AROUND FOR 5 MINUTES OR SO AT 5500RPMS AND THEN WILL CRUISE FOR A WHILE AT 1500 RPMS WHEN I GO TO THROTTLE UP TO 5500RPMS THE ENGINE WILL REV UP THEN BACK IT SELF DOWN AGAIN TO 1500 RPMS . I JUST HAD ALL THE CARBS CLEANED AND REBUILT . THE ENGINE IS GOING IN FOR WINTERIZATION AND STORAGE BUT THE MECHANIC SAID THAT WE COULD RUN IT FOR ONE MORE WEEKEND . THE MECHANIC WHO CLEANED THE CARBS TOOK OUT THE PLASTIC THERMOSTAT ( WHICH HAD MELTED ). HE SAID THAT AT ONE POINT THE ENGINE MUST HAVE OVERHEATED .HE SAID THAT HE WOULD CHECK IT OUT AND RELACE IT OVER THE WINTER . HE MENTIONED THAT I MIGHT NEED A HEAD GASKET TOO .THE ENGINE IDLED FINE DID NOT SMOKE RAN GOOD EXCEPT FOR THAT SLOWING DOWN PROBLEM ? IF THE MECHANIC HAD TESTED IT UNDER LOAD HE PROBABLY WOULD HAVE RUN INTO THE PROBLEM .

Re: 87 70 HP EVINRUDE VRO CUTTING DOWN AT FULL THROTTLE

Did he do a compression check? Did he check for an overheat condition. May be going into SLOW mode from overheating. Any warning horns going off? VRO OK??

Re: 87 70 HP EVINRUDE VRO CUTTING DOWN AT FULL THROTTLE

Your engine did not smoke...At ALL?<br /><br />That is not a good sign.<br /><br />TMD

Re: 87 70 HP EVINRUDE VRO CUTTING DOWN AT FULL THROTTLE

The engine did not smoke excessively just when it started . I put a mark on the vro tank and noticed it was going down . He did not tell me that he did a compression test but why would it fly for a while and then when I went to throttle up after going slow for a while would it back itself down to a slow speed gradually ? Could there be air leaks in the lines ?<br /><br /> thanks<br /><br /> gerry

Re: 87 70 HP EVINRUDE VRO CUTTING DOWN AT FULL THROTTLE

ZMANN,When engine started to fall off you could have tried pumpimg the primer bulb to see if engine picked up.This would indicate failing fuel pump or delivery problem to carbs.Also repeatedly bumping the primer switch could expose a problem with carbs ability to deliver fuel since it allows fuel flow to bypass the carbs.Insure that your fuel tank is venting properly and there are no restrictions in tank pickup tube.A colapsing or soft primer bulb while running would indicate such.

Re: 87 70 HP EVINRUDE VRO CUTTING DOWN AT FULL THROTTLE

Hey Zmaan,I have an 87' model 70h.p. Evinrude and it was having the exact same problem that your having.Did all routine checks and such and it ended up being water in fuel system.I took a clear fuel line and hooked it up on my inlet side of the pump and you could see the water.Used some water remover and problem was fixed.

Re: 87 70 HP EVINRUDE VRO CUTTING DOWN AT FULL THROTTLE

HEY GUYS<br /> THANKS FOR THE ADVICE . I JUST MADE AN APPOINTMENT TO HAVE THE BOAT WINTERIZED . THE MECHANIC IS GOING TO CHECK IT OUT SINCE HE HAS ALREADY WORKED ON IT AND GAVE IT A CLEAN BILL OF HEALTH HE WAS LEANING TOWARDS WATER IN THE LINE OR AIR HOLES IN THE HOSES ? THIS FORUM IS GREAT . I LOVE SMALL ENGINES SO MUCH I JUST SIGNED UP TO TAKE A SMALL ENGINE REPAIR COARSE. OUTBOARDS MIGHT BE A LITTLE OVER THE TOP BUT ITS ALWAYS GOOD TO HAVE A BASIC UNDERSTANDING.