90hp vro only 3000rpm

[Lee23]

My 1989 90hp V-4 vro will run fine for about five min at 5000rpm then it starts running rough and slows to about 3000rpm. If I stop for about 30 minutes it will run at 5000rpm for about five miutes and then it starts acting up again. I have squeezed the primer bulb when the problem occurs and swapped fuel tanks and fuel lines. The motor is not over heating. The vro and warning horn have been disconnected. Could it be going into slow mode?

 

[OBJ]

Re: 90hp vro only 3000rpm

Welcome Lee23 to iboats!<br /><br />What it's doing is dropping a cylinder. Two ways to find out which one.<br /><br />1 way - when it starts running rough, pull the hood and start pulling spark plug wires, one at a time. What your looking for is the one that don't make a difference in how the engine runs.<br /><br />2nd way - get an inductive timing light. When the engine starts acting up, just take the timing like and see what cylinder has no spark.<br /><br />I'm curious, is 5000rpm the max the engine will turn?

 

[rickdb1boat]

Re: 90hp vro only 3000rpm

Have to ask, How do you know it's not overheating??

 

[ob15]

Re: 90hp vro only 3000rpm

My thoughts are with Rick. How do you know it's not overheating?

 

[OBJ]

Re: 90hp vro only 3000rpm

Good question.

 

[Silvertip]

Re: 90hp vro only 3000rpm

Why was the overheat AND VRO warning disconnected. That's just asking for trouble. If you are pre-mixing all that needs to be disconnected is the VRO. Overheat is a separate function. Because the water pump is working does not mean the engine is cooling properly. Stuck thermostat is one probable cause. Losing a cylinder is another reason for the RPM drop.

 

[Lee23]

Re: 90hp vro only 3000rpm

The previous owner disconnected the vro, he said that after he did this the alarm kept sounding so he disconnected it. The engine will reach 5500rpm. The water stream squirting from the motor is warm. about the same as others that I've felt.

 

[Silvertip]

Re: 90hp vro only 3000rpm

OK -- another question then. Does the alarm provide a beep when the key is turned to the ON (not start) position. If not, get it fixed. That beep is the overheat warning and is independent of the VRO warnings. You need to have that working.

 

[rickdb1boat]

Re: 90hp vro only 3000rpm

Just because the pisser water feels right does not mean it's getting sufficient cooling. Might keep that in mind....5 minutes, slows down. 30 minutes rest, runs again. Repeat process, same thing... Huuummmm....

 

[OBJ]

Re: 90hp vro only 3000rpm

Makes sense. Lee, what you need to do when it stops is pull the hood and see if there is an excessive amout of heat coming from the block.<br /><br />(Boy....this'll teach me to take things a face value.... at 5:30am )

 

[alden135]

Re: 90hp vro only 3000rpm

You can buy some thermomelt sticks at your local auto parts store.

 

[Lee23]

Re: 90hp vro only 3000rpm

I found where the alarm wire was disconncted and I reconnected it. Now I get a beep when I turn on the key. I will take the boat out and see if I get an alarm when it starts acting up. Thanks for all of the information.