water pump shot?

[timbucktom]

My 79 100 hp Evinrude's water pump works fine at slower speeds, but when you open it up, the flow sometimes stops. If you quickly pull the throttle off back to an idle, the water flows again. I've checked the intake screens repeatedly and they're never clogged or anything. What's going on? I thought water pumps just quit and can't possilbly die a slow death. Anyone help?

 

[Vic.S]

Re: water pump shot?

Engine set so that the pump loses its water supply at high speeds? ie too high.

 

[kenmyfam]

Re: water pump shot?

My 79 100 hp Evinrude's water pump works fine at slower speeds, but when you open it up, the flow sometimes stops. If you quickly pull the throttle off back to an idle, the water flows again. I've checked the intake screens repeatedly and they're never clogged or anything. What's going on? I thought water pumps just quit and can't possilbly die a slow death. Anyone help?

Give us a little history on this. Couple of questions to begin with though.
When was the water pump last serviced ???
Is the motor overheating ???
Have you checked the head temperatures ???

 

[timbucktom]

Re: water pump shot?

Thanks for responding. Do you mean set too high as in trim?

 

[kenmyfam]

Re: water pump shot?

Thanks for responding. Do you mean set too high as in trim?

I think he means too high as in motor height and not having enough of the lower unit in the water when planing. Therefore your motor can not draw enough cooling water.

 

[timbucktom]

Re: water pump shot?

The motor will get hot if you keep running it, but I pull the throttle back as soon as I notice. Haven't checked the head tempuratures, but did have an alarm on the motor sound after I failed to notice the pump wasn't working. As for the last service, I don't know.

 

[timbucktom]

Re: water pump shot?

gotcha. I don't think so because it doesn't happen every time. It's tempermental. won't happen for days or weeks, then it happens for a while, then it doesn't. BTW the boat is a 15 foot Starcraft, if that helps

 

[kenmyfam]

Re: water pump shot?

gotcha. I don't think so because it doesn't happen every time. It's tempermental. won't happen for days or weeks, then it happens for a while, then it doesn't. BTW the boat is a 15 foot Starcraft, if that helps

So going back to my earlier post. How about some info ???

 

[timbucktom]

Re: water pump shot?

the loss of water supply makes the most sense as the pump is working at slower speeds. The motor is not original to the boat, which is an 1985. Is there a certain measurement below the hull that is required for water pumps to work properly? Is there a way to increase water supply?

 

[timbucktom]

Re: water pump shot?

What else do you want to know? I think you might have skipped one of my replies.

 

[kenmyfam]

Re: water pump shot?

the loss of water supply makes the most sense as the pump is working at slower speeds. The motor is not original to the boat, which is an 1985. Is there a certain measurement below the hull that is required for water pumps to work properly? Is there a way to increase water supply?

Basically the intake must be submerged at all speeds.
Back to one of my original questions. When was the water pump last serviced ???

 

[timbucktom]

Re: water pump shot?

don't know when the pump was last serviced. as for depth of the lower end in the water, it has to deep enough because it doesn't happen every time at high speeds. So it's definitely getting good water supply then. I wonder if the intake could have something caught inside the grates that's plugging it up and shutting off the supply on occasion.

 

[bktheking]

Re: water pump shot?

First thing almost anyone on here will tell you, if you don't know when it was serviced last, time for a new impeller at least, possibly an entire kit for starters.

 

[kenmyfam]

Re: water pump shot?

don't know when the pump was last serviced. as for depth of the lower end in the water, it has to deep enough because it doesn't happen every time at high speeds. So it's definitely getting good water supply then. I wonder if the intake could have something caught inside the grates that's plugging it up and shutting off the supply on occasion.

Time for a water pump service and a back flush. Should be part of routine maintenance. Check the thermostats while you are at it.