15 hp overheating after impeller replacement

[rustyscrew]

I have an evinrude 15hp 1998 outboard (E15RCEC). I replaced the impeller, but not the water pump. On test using the hose everything seemed to be fine with the indicator showing strong. I took it out on the lake and a quarter of a mile out, I noticed that it seemed very hot. The pee stream was intermittent, pulsing as we ran. Upon inspection, the water was scalding hot coming out. The engine didn't falter or sieze so I think I caught it early enough. I rowed back, removed the lower unit and inspected the water pump. Nothing looked out of line. I reassembled it and tried it again at the dock. Again it seemed to heat up very quickly and was pulsing. Usually it has a weak pee stream but has never overheated before.

I have a water pump on order and will start there, but I was curious if there are other ideas out there. It is perplexing and I am really hoping to have it ready by next weekend.

Some theories I have come up with:

1) Blockage? Earwig or such crawling up the intake.
2) Poor seal between waterpump rubber cup and the downpipe.
3) Thermostat? I have read about this, but I have never done anything with it.

How hot can the indicator water be without concern?

 

[rrw]

Re: 15 hp overheating after impeller replacement

Hi, being that it was working before replacement I'm leaning towards #2, bad seal between pump and tube, or something of that nature. I'm not sure how much heat for how long it can take, but if the pee stream was that hot the actual powerhead temp was probably dangerously hot, but if it still runs, and runs good you should be ok.

 

[Watermann]

Re: 15 hp overheating after impeller replacement

I found that it's best to replace the water pump and impeller in a kit form with all the new seals and grommets as well as the thermostat if it's never been done before. Also be sure the impeller vanes are going in the correct direction when reassembling. I've seen power heads get so hot the paint burns and discolors on them and they have run for years afterwards.

 

[rustyscrew]

Re: 15 hp overheating after impeller replacement

Thanks rrw and watermann. I haven't looked into changing the thermostat before. Is that a big job?

 

[tomhath]

Re: 15 hp overheating after impeller replacement

When you get the new water pump remove the tube and run something like a piece of weed whacker line through it. I've found the remains of old impellers in them even when the impeller I was replacing was still together. Don't assume the guy who did the job before you did it right.

 

[Watermann]

Re: 15 hp overheating after impeller replacement

Thanks rrw and watermann. I haven't looked into changing the thermostat before. Is that a big job?

Very easy on your motor, it looks to me like it's on top of the power head and has 3 bolts. Here is the schematic for it and parts list. Man they want some money for yours, I just bought a thermostats for a 70 HP rude that was only 10 bucks. Part # 19 and the seal comes with it.

Evinrude Cylinder & Crankcase Parts for 1989 15hp E15RCEC Outboard Motor

 

[the machinist]

Re: 15 hp overheating after impeller replacement

All the above info is good.

I just replaced a thermostat on my 92, boy are they proud of it, $40 for it and the seat, but that is the only way they sell it. Mine was stuck open, but that stat is sealed inside a plastic case, no way to even get to anything other than blow it out with air. However, I cut my old one open after replacing it & it was seized on the inner shaft, so it could seize either way. I think in the future, each fall I will pull it off & spray down with WD-40.

 

[EagleNuke]

Re: 15 hp overheating after impeller replacement

I just replaced mine in j15elcec and still have the last bolts to put in yet. My old one had the pin out when I got it, so I replaced that. Then when I started it, the old hardened impellor vanes didintegrated.

Watemann mentioned making sure the vanes are in the right direction...Which direction is that? I guessed and bent them so the ends point CW looking down, but since I haven't run it yet, this would be a great time to find out if it is wrong.

 

[Rick.]

Re: 15 hp overheating after impeller replacement

I just replaced mine in j15elcec and still have the last bolts to put in yet. My old one had the pin out when I got it, so I replaced that. Then when I started it, the old hardened impellor vanes didintegrated.

Watemann mentioned making sure the vanes are in the right direction...Which direction is that? I guessed and bent them so the ends point CW looking down, but since I haven't run it yet, this would be a great time to find out if it is wrong.

You did it right. IMO they will right themselves in seconds even if you do it wrong. Best of luck. Rick.

 

[geoffwga1]

Re: 15 hp overheating after impeller replacement

You did it right. IMO they will right themselves in seconds even if you do it wrong. Best of luck. Rick.

Generally yes.However I have on occasions opened up the pump and found 1 or more vanes facing the wrong way.Bear in mind that the shaft turns clockwise looking from above,therefore the vanes should be trailing,in other words they should be pointing acw.

 

[Watermann]

Re: 15 hp overheating after impeller replacement

Just as geoff said the drive shaft will always turn clockwise and the vanes must be folding backwards away from the rotation, not facing into it which could cause them to loose some longevity right off the bat reversing directions. I even go so far as to smear a thin layer of marine grease inside the cup just to give the new vanes something slippery to run on before the water gets up.

 

[EagleNuke]

Re: 15 hp overheating after impeller replacement

Thanks Geoff and Watetmann. I finished the engine last night as it was, and it is moving water very well now. I will probably not mess with it now, but the next time I will bend the vanes the other way.
So, back to Rustyscrew, any progress?

 

[Ryan0186]

Re: 15 hp overheating after impeller replacement

I had the same problem with my 15hp and found that the exhaust housing was so corroded that the hole and grommet for the water pickup tube no longer existed. Don't know how my motor was getting ny water at all. This was after I had replaced my entire water pump kit and housing. The motor would pump a little water while in a test tank but would get nothing while on the muffs. Does your motor pump on muffs? If your feeling up to it I would pull the powerhead and check the water tube grommets and tubes for blockages and corrosion.