Johnson 150 surges 800 RPM

[mollysyd]

Help! I'm new to boating forums. I recently bought a 94 fish & ski boat with a 94 Johnson 150HP V6 outboard. It overheated 1st time out. My mechanic found a stuck thermostat which burned out the rheostat because it is water cooled. He replaced both thermostats and I tried out the boat. Cooling problem is ok now but the engine has "power surges". (It did this on the day it overheated too). I tried to keep the tach at a steady 2600 RPM and every 20 -3o seconds or so it would speed up to 3400RPM and then fall back to 2600. You could feel the boat really lunge and then slow up. My fishing buddy tried pumping the fuel bulb and the boat picked up speed. We then switched fuel tanks from the built in unit to a portable gas tank and the engine did the same thing.
2nd Problem:
The VRO alarm sounds every other second while in the idle zone but goes off when I up the speed. If I turn the engine off in the idle zone and restart, the horn stays off for a couple of minutes and then starts beeping.
Should I just bypass the VRO? My local dealer priced a new one for $345.
Ouch!! He said they don't have VRO rebuild kits anymore.
Thanks for your help. Chuck

 

[tashasdaddy]

Re: Johnson 150 surges 800 RPM

you may have one of 2 problems, a coil starting to fail, fuel starvation, bad pump. betting on fuel starvation. it would be much cheaper to do away with the vro and go premixed.

 

[ezeke]

Re: Johnson 150 surges 800 RPM

Surging is often caused by air infiltration into the fuel/oil system.

The half second on-off alarm is a no oil warning. If the oil is not mixing properly, it may partly explain the overheating.

If you convert to conventional pumps, you will need two pumps and the system will not be as good as what you have.

If you convert to premix, the best choice would be the premix pump that looks like the VRO, but is strictly for premix Part # 5007422. It sells for around $260. from your local dealer.

 

[Joe Reeves]

Re: Johnson 150 surges 800 RPM

In addition to the above on target replies to which I agree.... the VRO pump has failed, my comments follow. I agree also as Zeke states "If you convert to premix, the best choice would be the premix pump that looks like the VRO, but is strictly for premix Part # 5007422. It sells for around $260. from your local dealer."

(VRO Horn Warnings)
(J. Reeves)

1 - A steady constant beep = Overheating - The V/6 engines, possibly some others, have a fuel restriction warning which is also a steady constant beep.
2 - A beep every 20 or 40 seconds = oil level has dropped to 1/4 tank. (Late model engine = Every 40 seconds)
3 - A beep every other second = VRO failure, air leak in oil line, oil restriction, (anything that would result in a lack of oil being supplied to the engine).

NOTE - If the warning horn is the black plastic (overpriced) three wire type horn, the warning horn should beep once when the ignition key is turned to the ON position. If it does not, it is either faulty or someone has disconnected it (a stupid move!). At any rate, if it does not beep which indicates that the horn is non functional, find out why and do not run the engine until the problem is corrected.

(Priming The VRO Pump)
(J. Reeves)

When hooking up or installing a VRO whether it is a new or original VRO pump, it must be primed in order to dispel any air that might be in the oil line.

Have the Oil line attached to the engine fitting BUT detached from the VRO. Add a piece of fuel hose if necessary to the oil line so that it can be aimed into some sort of container.

Pump the oil primer bulb, catching the oil flowing out of the line into the container until you are absolutely sure that you have rid the oil line of every bit of air that might have been trapped there.

Now, connect the oil line to the VRO and secure it. When the oil line is secured, apply pressure to the oil primer bulb ONE TIME only. That's it.

(VRO Pump Conversion To Straight Fuel Pump)
(J. Reeves)

You can convert the VRO pump into a straight fuel pump, eliminating the oil tank and VRO pump warning system, but retain the overheat warning setup by doing the following:

1 - Cut and plug the oil line at the engine so that the oil side of the VRO pump will not draw air into its system. Trace the wires from the back of the VRO to its rubber plug (electrical plug) and disconnect it.

2 - Trace the two wires from the oil tank to the engine, disconnect those two wires, then remove them and the oil tank.

3 - Mix the 50/1 oil in the proper amount with whatever quantity fuel you have. Disconnect the fuel line at the engine. Pump the fuel primer bulb until fuel exits that hose with the tint of whatever oil you used. Reconnect the fuel hose.

That's it. If you want to test the heat warning system to ease your mind, have the key in the on position, then ground out the tan heat sensor wire that you'll find protruding from the cylinder head. The warning horn should sound off.