Water pump problem?

[Spurger72]

Im not sure whats going on with this 18hp evinrude fastwin. Put it in a drum of water idling and its pumping water fine. So i decided to carry it and put in at the river. I took off from the landing and it was pushing my 14/52 flat bottum really well. I looked to see if it was pumping water and it wasn't(Holy Crap!!)no water was coming out of the tell tale, so i got off the throttle quickly, put the motor in neutral got the rpm's back to idle and it began to pump water again. This can't be good turned around and was heading back to the landing never made it back. Again it stop pumping water and was extremely hot and quit running. By the time i got to the landing(after paddling all the way back) it had cooled and i cranked it but then shut it off, i was just checking to make sure it hadnt seized up... So it just didn't make sense that it would pump water
with engine at an idle in a barrel of water then quit when i put it in the river and run it at full throttle then start back pumping water again after getting off the throttle and return to an idle. So should i replace the impeller and thermastat since both of these parts haven't been replaced since ive acquired this motor? Or is it something else causing this?

 

[CedarRiverScooter]

Sounds like a clog that blocks with pressure.

I would take the lower unit off inspect/ run a wire through every passage.

If a pc of impeller had broke off, it can get stuck.

inspect water pump & housing, water tube grommets, et al.

Also check the thermostat, maybe it is in backwards.

As long as I am kibitzing, check the little dowel pin that drives WP impeller, maybe it is slipping by at faster RPM.

 

[Spurger72]

Thanks for the advice. I'll give it a try. Thanks cedar river scooter.

 

[CedarRiverScooter]

NP
Just to be clear, a impeller pc can get stuck inside the power head passages. So keep that in mind if you don't find a simpler cause.

 

[Pappy]

Did it seem to pump okay at idle and just off idle then go away up on plane?
If so, take a look behind the propeller. Behind the prop is where your water inlet is. There is a screen there and behind the screen is a drilled passage.
There should be a plug in the drilled passage that is at the very end (or bottom) and you should be able to see and touch it. If all you see is a hole then a plug will have to be sourced and installed.
This passage angles back and as speed increases it will pick up air and starve the pump and powerhead. Easy check.
By all means replace the entire pump. Much has been written about when to replace a complete pump in lieu of just an impeller. The general rule is that when the impeller housing shows grooves than you can sort of hook a fingernail in and feel them...replace the complete pump.
Let us know what you see.

 

[chadzeilenga]

I have the same 18hp Fastwin. If I recall, these don't pump a steady stream. Is there a video of what it should look like?

 

[Shaugh]

I agree with Pappy, check your intake screen and make sure this plug is installed:

https://www.marineengine.com/newparts/part_details.php?pnum=OMC0300314

https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1970&hp=18&model=18002C&manufacturer=Evinrude&section=Gearcase+Group

It could also be as simple as a clogged or heavily painted screen. At idle when the boat is low in the water a restricted screen let's water fill up that tube. At speed a clogged screen could be preventing enough water from getting into the motor. Causing the pump to lose prime.

 

[Spurger72]

Update on my water pump. Turns out it was multiple problems. I went ahead and replaced the impeller and decided to check out the thermastat and it was shot. Replaced the thermastat and noticed something in the inlet where water enters the thermastat. So i took compressed air and blew it out and there was so much debris that came out, its a wonder any water could flow through this thing. Now i was trying to find and clear every hole on or the foot of this motor. The screen that you guys mentioned in earlier post did have the plug in it. Where the screen ended i noticed a cover plate with holes and two screws holding it, removed them to find even more debris. The hole that led down to the screen was severely clogged. It took awhile to get that 1 cleared. Finally got everything put back together and after dinner took it back to the river and it was FANTASTIC!! I bet i ran a half a tank through her. It never overheated had great waterflow and i decided, at a low speed, to carefully reach back to check the temp of the water leaving the motor and it was the temp for washing your hands, mildly warm...so very pleased with this 50year old Rude!! My wife and enjoyed the ride as well. Thanks to all of you who responded to my post.

 

[Shaugh]

It’s a good reminder for anyone that has a motor that’s sat around. Mice.... Mud wasps... Paper wasps.... ants....I can’t tell you all the things that love motors and those little passages.

Every motor I rebuild is packed with that garbage. My current work table. Mud wasps are the worst....